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Zarr Python · FreedomIntelligence | DecimalAI

Databy FreedomIntelligence

Zarr Python

Chunked N-D arrays for cloud storage. Compressed arrays, parallel I/O, S3/GCS integration, NumPy/Dask/Xarray compatible, for large-scale scientific computing pipelines.

SkillScore

SkillScore33/100

Test results 33

Safety

3/3 safety checks passed

Code scan
Intent
Content

What it changes

8%33%of test cases passed +25 pts

Without skill2 of 24

With skill8 of 24

7 fixed1 passed either way15 still failing1 broke

Measured on gemini-3.6-flash7/26/2026v1

Track record

Agent runs: 0; All time

Use this skill

Your agent runs on

Adds every file the skill has, pinned so you can update it. No account needed.

pip install "decimalai>=0.15"
decimalai skills add zarr-python
claude --plugin-dir "$(git rev-parse --show-toplevel 2>/dev/null || pwd)/.agents"

The same install from Python, for a notebook or a setup script.

Install

pip install "decimalai>=0.15"

Add the skill

from decimalai import skillpkg

# Writes .agents/skills and .decimal/skills.toml. Safe to run twice.
result = skillpkg.add("zarr-python")
if result.exit_code:
    raise SystemExit(result.problems)

print("Added. Start Claude Code with the command below.")

Start Claude Code with it

claude --plugin-dir "$(git rev-parse --show-toplevel 2>/dev/null || pwd)/.agents"

Type these in a Claude Code session. No account or API key. It writes the skill and any files it bundles, and asks first when its safety rating isn't Passed.

Add the DecimalAI plugin, once

/plugin marketplace add decimal-labs/decimalai-claude-plugins
/plugin install decimalai@decimalai

Install this skill

/decimalai:install zarr-python

The plugin needs python3 and curl on your machine.

No Python or account. Claude Code picks it up in its next session.

Save it into your project

curl -fsSL --create-dirs -o .claude/skills/zarr-python/SKILL.md https://app.decimal.ai/s/zarr-python/SKILL.md

Copy SKILL.md

Save it in your project, as

.claude/skills/zarr-python/SKILL.md

This gets SKILL.md only. The skill's 1 other file is not included.

Other ways to add it

Claude Code docs

agent_config() hands your agent the skill. With no DecimalAI key it reads your project's files and sends nothing. Needs SDK 0.27 or newer.

Install

pip install "decimalai[claude-agent-sdk]"
decimalai skills add zarr-python

Add it to your agent

import asyncio

from claude_agent_sdk import ClaudeAgentOptions
from decimalai.claude_agent_sdk import agent_config

# With no DECIMAL_API_KEY this reads the skills your project lists, from disk.
support = agent_config("support", fallback="You are a helpful agent.")

async def main():
    question = "Hello!"
    async with support.run(question) as run:  # one user message, one run
        async for message in run.query(options=ClaudeAgentOptions(max_turns=6)):
            print(message)

# In a notebook or async code: await main()
asyncio.run(main())

Prefer its own loader? ClaudeAgentOptions(plugins=[skills_plugin()], skills="all") reads the same folder. Use one or the other: a skill delivered both ways reaches the prompt twice.

The same install from Python, for a notebook or a setup script. agent_config() hands your agent the skill. With no DecimalAI key it reads your project's files and sends nothing. Needs SDK 0.27 or newer.

Install

pip install "decimalai[claude-agent-sdk]"

Add it to your agent

from decimalai import skillpkg

# Writes .agents/skills and .decimal/skills.toml. Safe to run twice.
result = skillpkg.add("zarr-python")
if result.exit_code:
    raise SystemExit(result.problems)

import asyncio

from claude_agent_sdk import ClaudeAgentOptions
from decimalai.claude_agent_sdk import agent_config

# With no DECIMAL_API_KEY this reads the skills your project lists, from disk.
support = agent_config("support", fallback="You are a helpful agent.")

async def main():
    question = "Hello!"
    async with support.run(question) as run:  # one user message, one run
        async for message in run.query(options=ClaudeAgentOptions(max_turns=6)):
            print(message)

# In a notebook or async code: await main()
asyncio.run(main())

Prefer its own loader? ClaudeAgentOptions(plugins=[skills_plugin()], skills="all") reads the same folder. Use one or the other: a skill delivered both ways reaches the prompt twice.

No DecimalAI package. The whole skill goes in every prompt, and nothing pins or updates it.

Copy SKILL.md

Save it in your project, as

.agents/skills/zarr-python/SKILL.md

Give it to your agent

import asyncio
from pathlib import Path
from claude_agent_sdk import ClaudeAgentOptions, query

skill = Path(".agents/skills/zarr-python/SKILL.md").read_text()
options = ClaudeAgentOptions(system_prompt=f"You are a helpful agent.\n\n{skill}", max_turns=6)

async def main():
    async for message in query(prompt="Hello!", options=options):
        print(message)

# In a notebook or async code: await main()
asyncio.run(main())

This gets SKILL.md only. The skill's 1 other file is not included.

Other ways to add it

Claude Agent SDK docs

agent_config() hands your agent the skill. With no DecimalAI key it reads your project's files and sends nothing. Needs SDK 0.27 or newer.

Install

pip install "decimalai[openai-agents]"
decimalai skills add zarr-python

Add it to your agent

from agents import Agent, Runner
from decimalai.openai_agents import agent_config

# With no DECIMAL_API_KEY this reads the skills your project lists, from disk.
support = agent_config("support", fallback="You are a helpful agent.")

agent = Agent(
    name=support.name,
    instructions=support.instructions,  # your prompt, then the skill list
    tools=[*support.tools],             # your tools, then load_skill
)
# In a notebook or async code: result = await Runner.run(agent, "Hello!")
result = Runner.run_sync(agent, "Hello!")

Using SandboxAgent? capabilities=[Shell(), decimalai.openai_agents.sandbox_skills()] points its own loader at the same folder.

Install

pip install "decimalai[openai-agents]"

Add it to your agent

from decimalai import skillpkg

# Writes .agents/skills and .decimal/skills.toml. Safe to run twice.
result = skillpkg.add("zarr-python")
if result.exit_code:
    raise SystemExit(result.problems)

from agents import Agent, Runner
from decimalai.openai_agents import agent_config

# With no DECIMAL_API_KEY this reads the skills your project lists, from disk.
support = agent_config("support", fallback="You are a helpful agent.")

agent = Agent(
    name=support.name,
    instructions=support.instructions,  # your prompt, then the skill list
    tools=[*support.tools],             # your tools, then load_skill
)
# In a notebook or async code: result = await Runner.run(agent, "Hello!")
result = Runner.run_sync(agent, "Hello!")

Using SandboxAgent? capabilities=[Shell(), decimalai.openai_agents.sandbox_skills()] points its own loader at the same folder.

No DecimalAI package. The whole skill goes in every prompt, and nothing pins or updates it.

Copy SKILL.md

Save it in your project, as

.agents/skills/zarr-python/SKILL.md

Give it to your agent

from pathlib import Path
from agents import Agent, Runner

skill = Path(".agents/skills/zarr-python/SKILL.md").read_text()
agent = Agent(name="support", instructions=f"You are a helpful agent.\n\n{skill}")
# In a notebook or async code: result = await Runner.run(agent, "Hello!")
result = Runner.run_sync(agent, "Hello!")

This gets SKILL.md only. The skill's 1 other file is not included.

Other ways to add it

OpenAI Agents docs

agent_config() hands your agent the skill. With no DecimalAI key it reads your project's files and sends nothing. Needs SDK 0.27 or newer.

Install

pip install "decimalai[openai]"
decimalai skills add zarr-python

Add it to your agent

import json

from openai import OpenAI
from decimalai.openai import agent_config

client = OpenAI()
# With no DECIMAL_API_KEY this reads the skills your project lists, from disk.
support = agent_config("support", fallback="You are a helpful agent.")


def lookup_order(order_id: str) -> str:
    return f"Order {order_id} shipped yesterday."


# Your tools, as Chat Completions takes them, and what answers each.
TOOLS = [{"type": "function", "function": {
    "name": "lookup_order",
    "description": "Look up the status of an order.",
    "parameters": {"type": "object", "properties": {"order_id": {"type": "string"}},
                   "required": ["order_id"]},
}}]
FUNCTIONS = {"lookup_order": lookup_order}

question = "Where is order A1001?"
with support.run(question) as run:  # one user message, one run
    # run.system is your prompt, then the skill list.
    messages = [{"role": "system", "content": run.system}, run.message]
    while True:
        reply = client.chat.completions.create(
            model="gpt-5.4-mini",
            messages=messages,
            tools=[*TOOLS, *run.tools],  # your tools, then load_skill
        ).choices[0].message
        messages.append(reply)
        if not reply.tool_calls:
            break
        for call in reply.tool_calls:
            # load_skill is answered by the run; your own tools by FUNCTIONS.
            function = FUNCTIONS.get(call.function.name)
            messages.append(run.tool_result(call) or {
                "role": "tool", "tool_call_id": call.id,
                "content": function(**json.loads(call.function.arguments)) if function
                else f"There is no tool named {call.function.name!r}.",
            })
print(reply.content)

# The Responses API takes run.response_tools instead of run.tools.

Install

pip install "decimalai[openai]"

Add it to your agent

from decimalai import skillpkg

# Writes .agents/skills and .decimal/skills.toml. Safe to run twice.
result = skillpkg.add("zarr-python")
if result.exit_code:
    raise SystemExit(result.problems)

import json

from openai import OpenAI
from decimalai.openai import agent_config

client = OpenAI()
# With no DECIMAL_API_KEY this reads the skills your project lists, from disk.
support = agent_config("support", fallback="You are a helpful agent.")


def lookup_order(order_id: str) -> str:
    return f"Order {order_id} shipped yesterday."


# Your tools, as Chat Completions takes them, and what answers each.
TOOLS = [{"type": "function", "function": {
    "name": "lookup_order",
    "description": "Look up the status of an order.",
    "parameters": {"type": "object", "properties": {"order_id": {"type": "string"}},
                   "required": ["order_id"]},
}}]
FUNCTIONS = {"lookup_order": lookup_order}

question = "Where is order A1001?"
with support.run(question) as run:  # one user message, one run
    # run.system is your prompt, then the skill list.
    messages = [{"role": "system", "content": run.system}, run.message]
    while True:
        reply = client.chat.completions.create(
            model="gpt-5.4-mini",
            messages=messages,
            tools=[*TOOLS, *run.tools],  # your tools, then load_skill
        ).choices[0].message
        messages.append(reply)
        if not reply.tool_calls:
            break
        for call in reply.tool_calls:
            # load_skill is answered by the run; your own tools by FUNCTIONS.
            function = FUNCTIONS.get(call.function.name)
            messages.append(run.tool_result(call) or {
                "role": "tool", "tool_call_id": call.id,
                "content": function(**json.loads(call.function.arguments)) if function
                else f"There is no tool named {call.function.name!r}.",
            })
print(reply.content)

# The Responses API takes run.response_tools instead of run.tools.

No DecimalAI package. The whole skill goes in every prompt, and nothing pins or updates it.

Copy SKILL.md

Save it in your project, as

.agents/skills/zarr-python/SKILL.md

Give it to your agent

from pathlib import Path
from openai import OpenAI

client = OpenAI()
skill = Path(".agents/skills/zarr-python/SKILL.md").read_text()
reply = client.chat.completions.create(
    model="gpt-5.4-mini",
    messages=[
        {"role": "system", "content": f"You are a helpful agent.\n\n{skill}"},
        {"role": "user", "content": "Hello!"},
    ],
).choices[0].message

This gets SKILL.md only. The skill's 1 other file is not included.

Other ways to add it

OpenAI SDK docs

agent_config() hands your agent the skill. With no DecimalAI key it reads your project's files and sends nothing. Needs SDK 0.27 or newer.

Install

pip install "decimalai[anthropic]"
decimalai skills add zarr-python

Add it to your agent

import anthropic
from decimalai.anthropic import agent_config

client = anthropic.Anthropic()
# With no DECIMAL_API_KEY this reads the skills your project lists, from disk.
support = agent_config("support", fallback="You are a helpful agent.")

question = "Hello!"
with support.run(question) as run:  # one user message, one run
    answer = client.beta.messages.tool_runner(
        model="claude-haiku-5-5",
        max_tokens=4096,
        system=run.system,     # your prompt, then the skill list
        tools=[*run.tools],    # your tools, then load_skill
        messages=[{"role": "user", "content": question}],
    ).until_done()

Install

pip install "decimalai[anthropic]"

Add it to your agent

from decimalai import skillpkg

# Writes .agents/skills and .decimal/skills.toml. Safe to run twice.
result = skillpkg.add("zarr-python")
if result.exit_code:
    raise SystemExit(result.problems)

import anthropic
from decimalai.anthropic import agent_config

client = anthropic.Anthropic()
# With no DECIMAL_API_KEY this reads the skills your project lists, from disk.
support = agent_config("support", fallback="You are a helpful agent.")

question = "Hello!"
with support.run(question) as run:  # one user message, one run
    answer = client.beta.messages.tool_runner(
        model="claude-haiku-5-5",
        max_tokens=4096,
        system=run.system,     # your prompt, then the skill list
        tools=[*run.tools],    # your tools, then load_skill
        messages=[{"role": "user", "content": question}],
    ).until_done()

No DecimalAI package. The whole skill goes in every prompt, and nothing pins or updates it.

Copy SKILL.md

Save it in your project, as

.agents/skills/zarr-python/SKILL.md

Give it to your agent

from pathlib import Path
import anthropic

client = anthropic.Anthropic()
skill = Path(".agents/skills/zarr-python/SKILL.md").read_text()
reply = client.messages.create(
    model="claude-haiku-5-5",
    max_tokens=4096,
    system=f"You are a helpful agent.\n\n{skill}",
    messages=[{"role": "user", "content": "Hello!"}],
)

This gets SKILL.md only. The skill's 1 other file is not included.

Other ways to add it

Anthropic docs

agent_config() hands your agent the skill. With no DecimalAI key it reads your project's files and sends nothing. Needs SDK 0.27 or newer.

Install

pip install "decimalai[google-genai]"
decimalai skills add zarr-python

Add it to your agent

from google import genai
from google.genai import types
from decimalai.google_genai import agent_config

client = genai.Client()
# With no DECIMAL_API_KEY this reads the skills your project lists, from disk.
support = agent_config("support", fallback="You are a helpful agent.")


def lookup_order(order_id: str) -> str:
    return f"Order {order_id} shipped yesterday."


# Your functions, as declarations for the model, and what answers each.
TOOLS = [{"function_declarations": [{
    "name": "lookup_order",
    "description": "Look up the status of an order.",
    "parameters_json_schema": {"type": "object", "properties": {"order_id": {"type": "string"}},
                               "required": ["order_id"]},
}]}]
FUNCTIONS = {"lookup_order": lookup_order}

question = "Where is order A1001?"
with support.run(question) as run:  # one user message, one run
    config = types.GenerateContentConfig(
        system_instruction=run.system,     # your prompt, then the skill list
        tools=[*TOOLS, *run.tool_params],  # your functions, then load_skill
    )
    contents = [{"role": "user", "parts": [{"text": run.message}]}]
    while True:
        response = client.models.generate_content(
            model="gemini-3.5-flash", contents=contents, config=config,
        )
        if not response.function_calls:
            break
        contents.append(response.candidates[0].content)
        parts = []
        for call in response.function_calls:
            # load_skill is answered by the run; your own functions by FUNCTIONS.
            # A loop of your own rather than automatic function calling, which
            # raises KeyError when the model asks for a function you did not pass.
            function = FUNCTIONS.get(call.name)
            parts.append(run.tool_result(call) or {"function_response": {
                "name": call.name, "id": call.id,
                "response": {"result": function(**(call.args or {})) if function
                             else f"There is no function named {call.name!r}."},
            }})
        contents.append({"role": "user", "parts": parts})
print(response.text)

Install

pip install "decimalai[google-genai]"

Add it to your agent

from decimalai import skillpkg

# Writes .agents/skills and .decimal/skills.toml. Safe to run twice.
result = skillpkg.add("zarr-python")
if result.exit_code:
    raise SystemExit(result.problems)

from google import genai
from google.genai import types
from decimalai.google_genai import agent_config

client = genai.Client()
# With no DECIMAL_API_KEY this reads the skills your project lists, from disk.
support = agent_config("support", fallback="You are a helpful agent.")


def lookup_order(order_id: str) -> str:
    return f"Order {order_id} shipped yesterday."


# Your functions, as declarations for the model, and what answers each.
TOOLS = [{"function_declarations": [{
    "name": "lookup_order",
    "description": "Look up the status of an order.",
    "parameters_json_schema": {"type": "object", "properties": {"order_id": {"type": "string"}},
                               "required": ["order_id"]},
}]}]
FUNCTIONS = {"lookup_order": lookup_order}

question = "Where is order A1001?"
with support.run(question) as run:  # one user message, one run
    config = types.GenerateContentConfig(
        system_instruction=run.system,     # your prompt, then the skill list
        tools=[*TOOLS, *run.tool_params],  # your functions, then load_skill
    )
    contents = [{"role": "user", "parts": [{"text": run.message}]}]
    while True:
        response = client.models.generate_content(
            model="gemini-3.5-flash", contents=contents, config=config,
        )
        if not response.function_calls:
            break
        contents.append(response.candidates[0].content)
        parts = []
        for call in response.function_calls:
            # load_skill is answered by the run; your own functions by FUNCTIONS.
            # A loop of your own rather than automatic function calling, which
            # raises KeyError when the model asks for a function you did not pass.
            function = FUNCTIONS.get(call.name)
            parts.append(run.tool_result(call) or {"function_response": {
                "name": call.name, "id": call.id,
                "response": {"result": function(**(call.args or {})) if function
                             else f"There is no function named {call.name!r}."},
            }})
        contents.append({"role": "user", "parts": parts})
print(response.text)

No DecimalAI package. The whole skill goes in every prompt, and nothing pins or updates it.

Copy SKILL.md

Save it in your project, as

.agents/skills/zarr-python/SKILL.md

Give it to your agent

from pathlib import Path
from google import genai
from google.genai import types

client = genai.Client()
skill = Path(".agents/skills/zarr-python/SKILL.md").read_text()
response = client.models.generate_content(
    model="gemini-3.5-flash",
    contents="Hello!",
    config=types.GenerateContentConfig(system_instruction=f"You are a helpful agent.\n\n{skill}"),
)

This gets SKILL.md only. The skill's 1 other file is not included.

Other ways to add it

Gemini API docs

agent_config() hands your agent the skill. With no DecimalAI key it reads your project's files and sends nothing. Needs SDK 0.27 or newer.

Install

pip install "decimalai[langchain]" langchain-openai
decimalai skills add zarr-python

Add it to your agent

from langchain.agents import create_agent
from decimalai.langchain import agent_config

# With no DECIMAL_API_KEY this reads the skills your project lists, from disk.
support = agent_config("support", fallback="You are a helpful agent.")

agent = create_agent(
    "openai:gpt-5.4-mini",
    tools=[],                         # your tools; the middleware adds load_skill
    middleware=[support.middleware],  # your prompt, the skill list and load_skill
)
result = agent.invoke({"messages": [{"role": "user", "content": "Hello!"}]})

Install

pip install "decimalai[langchain]" langchain-openai

Add it to your agent

from decimalai import skillpkg

# Writes .agents/skills and .decimal/skills.toml. Safe to run twice.
result = skillpkg.add("zarr-python")
if result.exit_code:
    raise SystemExit(result.problems)

from langchain.agents import create_agent
from decimalai.langchain import agent_config

# With no DECIMAL_API_KEY this reads the skills your project lists, from disk.
support = agent_config("support", fallback="You are a helpful agent.")

agent = create_agent(
    "openai:gpt-5.4-mini",
    tools=[],                         # your tools; the middleware adds load_skill
    middleware=[support.middleware],  # your prompt, the skill list and load_skill
)
result = agent.invoke({"messages": [{"role": "user", "content": "Hello!"}]})

No DecimalAI package. The whole skill goes in every prompt, and nothing pins or updates it.

Copy SKILL.md

Save it in your project, as

.agents/skills/zarr-python/SKILL.md

Give it to your agent

from pathlib import Path
from langchain.agents import create_agent

skill = Path(".agents/skills/zarr-python/SKILL.md").read_text()
agent = create_agent("openai:gpt-5.4-mini", tools=[], system_prompt=f"You are a helpful agent.\n\n{skill}")
result = agent.invoke({"messages": [{"role": "user", "content": "Hello!"}]})

This gets SKILL.md only. The skill's 1 other file is not included.

Other ways to add it

LangChain docs

CrewAI's own skill loader reads the installed folder. No DecimalAI account needed.

Install

pip install "decimalai>=0.16" "crewai>=1.15.27"
decimalai skills add zarr-python

Add it to your agent

import decimalai.crewai
from crewai import Agent, Crew, Task

agent = Agent(
    role="Support", goal="Help the customer", backstory="A support agent.",
    llm=llm,                               # your own CrewAI LLM
    skills=decimalai.crewai.skills(),      # the installed folder
    tools=decimalai.crewai.skill_tools(),  # reads a skill's files, runs its scripts
)
task = Task(description="Hello!", expected_output="an answer", agent=agent)
Crew(agents=[agent], tasks=[task]).kickoff()

The same install from Python, for a notebook or a setup script. CrewAI's own skill loader reads the installed folder. No DecimalAI account needed.

Install

pip install "decimalai>=0.16" "crewai>=1.15.27"

Add it to your agent

from decimalai import skillpkg

# Writes .agents/skills and .decimal/skills.toml. Safe to run twice.
result = skillpkg.add("zarr-python")
if result.exit_code:
    raise SystemExit(result.problems)

import decimalai.crewai
from crewai import Agent, Crew, Task

agent = Agent(
    role="Support", goal="Help the customer", backstory="A support agent.",
    llm=llm,                               # your own CrewAI LLM
    skills=decimalai.crewai.skills(),      # the installed folder
    tools=decimalai.crewai.skill_tools(),  # reads a skill's files, runs its scripts
)
task = Task(description="Hello!", expected_output="an answer", agent=agent)
Crew(agents=[agent], tasks=[task]).kickoff()

No DecimalAI package. CrewAI's own loader reads the folder, and nothing pins or updates it.

Copy SKILL.md

Save it in your project, as

.agents/skills/zarr-python/SKILL.md

Give it to your agent

from pathlib import Path
from crewai import Agent, Crew, Task

agent = Agent(
    role="Support", goal="Help the customer", backstory="A support agent.",
    llm=llm,                         # your own CrewAI LLM
    skills=[Path(".agents/skills")],
)
task = Task(description="Hello!", expected_output="an answer", agent=agent)
Crew(agents=[agent], tasks=[task]).kickoff()

This gets SKILL.md only. The skill's 1 other file is not included.

Other ways to add it

CrewAI docs

agent_config() hands your agent the skill. With no DecimalAI key it reads your project's files and sends nothing. Needs SDK 0.27 or newer.

Install

pip install "decimalai[adk]"
decimalai skills add zarr-python

Add it to your agent

from decimalai.adk import DecimalAIPlugin, agent_config
from google.adk.agents import LlmAgent
from google.adk.apps import App

# With no DECIMAL_API_KEY this reads the skills your project lists, from disk.
support = agent_config("support", fallback="You are a helpful agent.")

agent = LlmAgent(
    name="support",          # ADK needs a Python identifier
    model="gemini-3.5-flash",
    instruction=support.instruction,  # your prompt, then the skill list
    tools=[*support.tools],           # your tools, then load_skill
)
# DecimalAIPlugin makes each invocation of runners built from this App one trace.
app = App(name="support", root_agent=agent, plugins=[DecimalAIPlugin()])

Prefer ADK's own loader? SkillToolset(skills=decimalai.adk.skills(), ...) reads the same folder. Use one or the other: a skill delivered both ways reaches the prompt twice.

Install

pip install "decimalai[adk]"

Add it to your agent

from decimalai import skillpkg

# Writes .agents/skills and .decimal/skills.toml. Safe to run twice.
result = skillpkg.add("zarr-python")
if result.exit_code:
    raise SystemExit(result.problems)

from decimalai.adk import DecimalAIPlugin, agent_config
from google.adk.agents import LlmAgent
from google.adk.apps import App

# With no DECIMAL_API_KEY this reads the skills your project lists, from disk.
support = agent_config("support", fallback="You are a helpful agent.")

agent = LlmAgent(
    name="support",          # ADK needs a Python identifier
    model="gemini-3.5-flash",
    instruction=support.instruction,  # your prompt, then the skill list
    tools=[*support.tools],           # your tools, then load_skill
)
# DecimalAIPlugin makes each invocation of runners built from this App one trace.
app = App(name="support", root_agent=agent, plugins=[DecimalAIPlugin()])

Prefer ADK's own loader? SkillToolset(skills=decimalai.adk.skills(), ...) reads the same folder. Use one or the other: a skill delivered both ways reaches the prompt twice.

No DecimalAI package. The whole skill goes in every prompt, and nothing pins or updates it.

Copy SKILL.md

Save it in your project, as

.agents/skills/zarr-python/SKILL.md

Give it to your agent

from pathlib import Path
from google.adk.agents import LlmAgent

skill = Path(".agents/skills/zarr-python/SKILL.md").read_text()
agent = LlmAgent(
    name="support",
    model="gemini-3.5-flash",
    instruction=lambda context: f"You are a helpful agent.\n\n{skill}",
)

This gets SKILL.md only. The skill's 1 other file is not included.

Other ways to add it

Google ADK docs

agent_config() hands your agent the skill. With no DecimalAI key it reads your project's files and sends nothing. Needs SDK 0.27 or newer.

Install

pip install "decimalai[pydantic-ai]"
decimalai skills add zarr-python

Add it to your agent

from pydantic_ai import Agent
from decimalai.pydantic_ai import agent_config

# With no DECIMAL_API_KEY this reads the skills your project lists, from disk.
support = agent_config("support", fallback="You are a helpful agent.")

agent = Agent(
    "openai:gpt-4o-mini",
    name=support.name,
    tools=[],                 # your tools; the capability adds load_skill
    capabilities=[support],   # your prompt, the skill list and load_skill
)
# In a notebook or async code: result = await agent.run("Hello!")
result = agent.run_sync("Hello!")

On the Pydantic AI harness, decimalai.pydantic_ai_harness.skills(project) uses its own loader instead.

Install

pip install "decimalai[pydantic-ai]"

Add it to your agent

from decimalai import skillpkg

# Writes .agents/skills and .decimal/skills.toml. Safe to run twice.
result = skillpkg.add("zarr-python")
if result.exit_code:
    raise SystemExit(result.problems)

from pydantic_ai import Agent
from decimalai.pydantic_ai import agent_config

# With no DECIMAL_API_KEY this reads the skills your project lists, from disk.
support = agent_config("support", fallback="You are a helpful agent.")

agent = Agent(
    "openai:gpt-4o-mini",
    name=support.name,
    tools=[],                 # your tools; the capability adds load_skill
    capabilities=[support],   # your prompt, the skill list and load_skill
)
# In a notebook or async code: result = await agent.run("Hello!")
result = agent.run_sync("Hello!")

On the Pydantic AI harness, decimalai.pydantic_ai_harness.skills(project) uses its own loader instead.

No DecimalAI package. The whole skill goes in every prompt, and nothing pins or updates it.

Copy SKILL.md

Save it in your project, as

.agents/skills/zarr-python/SKILL.md

Give it to your agent

from pathlib import Path
from pydantic_ai import Agent

skill = Path(".agents/skills/zarr-python/SKILL.md").read_text()
agent = Agent("openai:gpt-4o-mini", instructions=f"You are a helpful agent.\n\n{skill}")
# In a notebook or async code: result = await agent.run("Hello!")
result = agent.run_sync("Hello!")

This gets SKILL.md only. The skill's 1 other file is not included.

Other ways to add it

Pydantic AI docs

Deep Agents' own skill loader reads the installed folder. No DecimalAI account needed.

Install

pip install "decimalai>=0.16" deepagents
decimalai skills add zarr-python

Add it to your agent

import decimalai.deepagents
from deepagents import create_deep_agent

agent = create_deep_agent(model=model, **decimalai.deepagents.skills())
agent.invoke({"messages": [{"role": "user", "content": "Hello!"}]})

The default backend reads files but has no shell. To run a skill's scripts, pass skills(backend=LocalShellBackend(...)).

The same install from Python, for a notebook or a setup script. Deep Agents' own skill loader reads the installed folder. No DecimalAI account needed.

Install

pip install "decimalai>=0.16" deepagents

Add it to your agent

from decimalai import skillpkg

# Writes .agents/skills and .decimal/skills.toml. Safe to run twice.
result = skillpkg.add("zarr-python")
if result.exit_code:
    raise SystemExit(result.problems)

import decimalai.deepagents
from deepagents import create_deep_agent

agent = create_deep_agent(model=model, **decimalai.deepagents.skills())
agent.invoke({"messages": [{"role": "user", "content": "Hello!"}]})

The default backend reads files but has no shell. To run a skill's scripts, pass skills(backend=LocalShellBackend(...)).

No DecimalAI package. The whole skill goes in every prompt, and nothing pins or updates it.

Copy SKILL.md

Save it in your project, as

.agents/skills/zarr-python/SKILL.md

Give it to your agent

from pathlib import Path
from deepagents import create_deep_agent

skill = Path(".agents/skills/zarr-python/SKILL.md").read_text()
agent = create_deep_agent(model=model, system_prompt=f"You are a helpful agent.\n\n{skill}")
agent.invoke({"messages": [{"role": "user", "content": "Hello!"}]})

This gets SKILL.md only. The skill's 1 other file is not included.

Other ways to add it

Deep Agents docs

Its own skill loader reads the installed folder. No DecimalAI account needed.

Install

pip install "decimalai>=0.16" agent-framework
decimalai skills add zarr-python

Add it to your agent

import asyncio

from agent_framework import Agent
from decimalai.agent_framework import skills

agent = Agent(client=client, instructions="You are a helpful agent.", context_providers=[skills()])
asyncio.run(agent.run("Hello!"))

It caches skills by default, so restart the process after decimalai skills update.

The same install from Python, for a notebook or a setup script. Its own skill loader reads the installed folder. No DecimalAI account needed.

Install

pip install "decimalai>=0.16" agent-framework

Add it to your agent

from decimalai import skillpkg

# Writes .agents/skills and .decimal/skills.toml. Safe to run twice.
result = skillpkg.add("zarr-python")
if result.exit_code:
    raise SystemExit(result.problems)

import asyncio

from agent_framework import Agent
from decimalai.agent_framework import skills

agent = Agent(client=client, instructions="You are a helpful agent.", context_providers=[skills()])
asyncio.run(agent.run("Hello!"))

It caches skills by default, so restart the process after decimalai skills update.

No DecimalAI package. The whole skill goes in every prompt, and nothing pins or updates it.

Copy SKILL.md

Save it in your project, as

.agents/skills/zarr-python/SKILL.md

Give it to your agent

import asyncio
from pathlib import Path
from agent_framework import Agent

skill = Path(".agents/skills/zarr-python/SKILL.md").read_text()
agent = Agent(client=client, instructions=f"You are a helpful agent.\n\n{skill}")
asyncio.run(agent.run("Hello!"))

This gets SKILL.md only. The skill's 1 other file is not included.

Other ways to add it

Microsoft Agent Framework docs

Strands' own skill loader reads the installed folder. No DecimalAI account needed.

Install

pip install "decimalai>=0.16" strands-agents
decimalai skills add zarr-python

Add it to your agent

from decimalai.strands import skills
from strands import Agent
from strands.vended_tools import file_editor, shell

agent = Agent(
    model=model,                # always pass one: the default is Amazon Bedrock
    system_prompt="You are a helpful agent.",
    tools=[file_editor, shell],
    plugins=[skills()],
)
agent("Hello!")

Strands loads an agent's skills once, so build the agent again after decimalai skills update.

The same install from Python, for a notebook or a setup script. Strands' own skill loader reads the installed folder. No DecimalAI account needed.

Install

pip install "decimalai>=0.16" strands-agents

Add it to your agent

from decimalai import skillpkg

# Writes .agents/skills and .decimal/skills.toml. Safe to run twice.
result = skillpkg.add("zarr-python")
if result.exit_code:
    raise SystemExit(result.problems)

from decimalai.strands import skills
from strands import Agent
from strands.vended_tools import file_editor, shell

agent = Agent(
    model=model,                # always pass one: the default is Amazon Bedrock
    system_prompt="You are a helpful agent.",
    tools=[file_editor, shell],
    plugins=[skills()],
)
agent("Hello!")

Strands loads an agent's skills once, so build the agent again after decimalai skills update.

No DecimalAI package. The whole skill goes in every prompt, and nothing pins or updates it.

Copy SKILL.md

Save it in your project, as

.agents/skills/zarr-python/SKILL.md

Give it to your agent

from pathlib import Path
from strands import Agent

skill = Path(".agents/skills/zarr-python/SKILL.md").read_text()
agent = Agent(model=model, system_prompt=f"You are a helpful agent.\n\n{skill}")
agent("Hello!")

This gets SKILL.md only. The skill's 1 other file is not included.

Other ways to add it

Strands docs

Adds every file the skill has, pinned so you can update it. Cursor, Copilot, Cline and Warp read this folder by themselves.

pip install "decimalai>=0.15"
decimalai skills add zarr-python

No Python or account. Cursor, Copilot, Cline and Warp read this folder by themselves.

Save it into your project

curl -fsSL --create-dirs -o .agents/skills/zarr-python/SKILL.md https://app.decimal.ai/s/zarr-python/SKILL.md

Copy SKILL.md

Save it in your project, as

.agents/skills/zarr-python/SKILL.md

This gets SKILL.md only. The skill's 1 other file is not included.

Other ways to add it

Cursor and other editors docs

Fetch the file and give its text to your model as instructions. No account or package needed.

Get the file

curl -fsSL https://app.decimal.ai/s/zarr-python/SKILL.md

Read the summary as JSON

curl -fsSL https://app.decimal.ai/s/zarr-python.json

This gets SKILL.md only. The skill's 1 other file is not included.

Other ways to add it

Other setups docs

You don't need a DecimalAI account.

Version: v1, tested 7/26/2026
Source: FreedomIntelligence/OpenClaw-Medical-Skills ↗
License: MIT license

Manage it in DecimalAI

Saved prompts and skills, pinned versions, and traces of this skill in your runs. DecimalAI does not run your agent.

Claude Code reads files from your project, so DecimalAI config does not apply there.

On Claude Agent SDK: save the skill to an agent here, set DECIMAL_API_KEY, and the same code uses it with no command to run. Changes you save reach the next run with no redeploy.

On OpenAI Agents: save the skill to an agent here, set DECIMAL_API_KEY, and the same code uses it with no command to run. Changes you save reach the next run with no redeploy.

On OpenAI SDK: save the skill to an agent here, set DECIMAL_API_KEY, and the same code uses it with no command to run. Changes you save reach the next run with no redeploy.

On Anthropic: save the skill to an agent here, set DECIMAL_API_KEY, and the same code uses it with no command to run. Changes you save reach the next run with no redeploy.

On Gemini API: save the skill to an agent here, set DECIMAL_API_KEY, and the same code uses it with no command to run. Changes you save reach the next run with no redeploy.

On LangChain: save the skill to an agent here, set DECIMAL_API_KEY, and the same code uses it with no command to run. Changes you save reach the next run with no redeploy.

On CrewAI: set DECIMAL_API_KEY and add decimalai.init(crewai=True) to record runs and skill use. The skill version stays in your repo.

On Google ADK: save the skill to an agent here, set DECIMAL_API_KEY, and the same code uses it with no command to run. Changes you save reach the next run with no redeploy.

On Pydantic AI: save the skill to an agent here, set DECIMAL_API_KEY, and the same code uses it with no command to run. Changes you save reach the next run with no redeploy.

On Deep Agents: set DECIMAL_API_KEY and add decimalai.init(langchain=True) to record runs and skill use. The skill version stays in your repo.

On Microsoft Agent Framework: set DECIMAL_API_KEY and add decimalai.init(otel=True, agent_name="support") to record runs and skill use. The skill version stays in your repo.

On Strands: set DECIMAL_API_KEY and add decimalai.init(otel=True, agent_name="support") to record runs and skill use. The skill version stays in your repo.

Editors read files from your project, so DecimalAI config does not apply there.

Anywhere else: record a use with decimalai.log_skill_activation() inside a trace.

Use this skill

SKILL.md

Zarr Python

Overview

Zarr is a Python library for storing large N-dimensional arrays with chunking and compression. Apply this skill for efficient parallel I/O, cloud-native workflows, and seamless integration with NumPy, Dask, and Xarray.

Quick Start

Installation

uv pip install zarr

Requires Python 3.11+. For cloud storage support, install additional packages:

uv pip install s3fs  # For S3
uv pip install gcsfs  # For Google Cloud Storage

Basic Array Creation

import zarr
import numpy as np

# Create a 2D array with chunking and compression
z = zarr.create_array(
    store="data/my_array.zarr",
    shape=(10000, 10000),
    chunks=(1000, 1000),
    dtype="f4"
)

# Write data using NumPy-style indexing
z[:, :] = np.random.random((10000, 10000))

# Read data
data = z[0:100, 0:100]  # Returns NumPy array

Core Operations

Creating Arrays

Zarr provides multiple convenience functions for array creation:

# Create empty array
z = zarr.zeros(shape=(10000, 10000), chunks=(1000, 1000), dtype='f4',
               store='data.zarr')

# Create filled arrays
z = zarr.ones((5000, 5000), chunks=(500, 500))
z = zarr.full((1000, 1000), fill_value=42, chunks=(100, 100))

# Create from existing data
data = np.arange(10000).reshape(100, 100)
z = zarr.array(data, chunks=(10, 10), store='data.zarr')

# Create like another array
z2 = zarr.zeros_like(z)  # Matches shape, chunks, dtype of z

Opening Existing Arrays

# Open array (read/write mode by default)
z = zarr.open_array('data.zarr', mode='r+')

# Read-only mode
z = zarr.open_array('data.zarr', mode='r')

# The open() function auto-detects arrays vs groups
z = zarr.open('data.zarr')  # Returns Array or Group

Reading and Writing Data

Zarr arrays support NumPy-like indexing:

# Write entire array
z[:] = 42

# Write slices
z[0, :] = np.arange(100)
z[10:20, 50:60] = np.random.random((10, 10))

# Read data (returns NumPy array)
data = z[0:100, 0:100]
row = z[5, :]

# Advanced indexing
z.vindex[[0, 5, 10], [2, 8, 15]]  # Coordinate indexing
z.oindex[0:10, [5, 10, 15]]       # Orthogonal indexing
z.blocks[0, 0]                     # Block/chunk indexing

Resizing and Appending

# Resize array
z.resize(15000, 15000)  # Expands or shrinks dimensions

# Append data along an axis
z.append(np.random.random((1000, 10000)), axis=0)  # Adds rows

Chunking Strategies

Chunking is critical for performance. Choose chunk sizes and shapes based on access patterns.

Chunk Size Guidelines

Minimum chunk size: 1 MB recommended for optimal performance
Balance: Larger chunks = fewer metadata operations; smaller chunks = better parallel access
Memory consideration: Entire chunks must fit in memory during compression

# Configure chunk size (aim for ~1MB per chunk)
# For float32 data: 1MB = 262,144 elements = 512×512 array
z = zarr.zeros(
    shape=(10000, 10000),
    chunks=(512, 512),  # ~1MB chunks
    dtype='f4'
)

Aligning Chunks with Access Patterns

Critical: Chunk shape dramatically affects performance based on how data is accessed.

# If accessing rows frequently (first dimension)
z = zarr.zeros((10000, 10000), chunks=(10, 10000))  # Chunk spans columns

# If accessing columns frequently (second dimension)
z = zarr.zeros((10000, 10000), chunks=(10000, 10))  # Chunk spans rows

# For mixed access patterns (balanced approach)
z = zarr.zeros((10000, 10000), chunks=(1000, 1000))  # Square chunks

Performance example: For a (200, 200, 200) array, reading along the first dimension:

Using chunks (1, 200, 200): ~107ms
Using chunks (200, 200, 1): ~1.65ms (65× faster!)

Sharding for Large-Scale Storage

When arrays have millions of small chunks, use sharding to group chunks into larger storage objects:

from zarr.codecs import ShardingCodec, BytesCodec
from zarr.codecs.blosc import BloscCodec

# Create array with sharding
z = zarr.create_array(
    store='data.zarr',
    shape=(100000, 100000),
    chunks=(100, 100),  # Small chunks for access
    shards=(1000, 1000),  # Groups 100 chunks per shard
    dtype='f4'
)

Benefits:

Reduces file system overhead from millions of small files
Improves cloud storage performance (fewer object requests)
Prevents filesystem block size waste

Important: Entire shards must fit in memory before writing.

Compression

Zarr applies compression per chunk to reduce storage while maintaining fast access.

Configuring Compression

from zarr.codecs.blosc import BloscCodec
from zarr.codecs import GzipCodec, ZstdCodec

# Default: Blosc with Zstandard
z = zarr.zeros((1000, 1000), chunks=(100, 100))  # Uses default compression

# Configure Blosc codec
z = zarr.create_array(
    store='data.zarr',
    shape=(1000, 1000),
    chunks=(100, 100),
    dtype='f4',
    codecs=[BloscCodec(cname='zstd', clevel=5, shuffle='shuffle')]
)

# Available Blosc compressors: 'blosclz', 'lz4', 'lz4hc', 'snappy', 'zlib', 'zstd'

# Use Gzip compression
z = zarr.create_array(
    store='data.zarr',
    shape=(1000, 1000),
    chunks=(100, 100),
    dtype='f4',
    codecs=[GzipCodec(level=6)]
)

# Disable compression
z = zarr.create_array(
    store='data.zarr',
    shape=(1000, 1000),
    chunks=(100, 100),
    dtype='f4',
    codecs=[BytesCodec()]  # No compression
)

Compression Performance Tips

Blosc (default): Fast compression/decompression, good for interactive workloads
Zstandard: Better compression ratios, slightly slower than LZ4
Gzip: Maximum compression, slower performance
LZ4: Fastest compression, lower ratios
Shuffle: Enable shuffle filter for better compression on numeric data

# Optimal for numeric scientific data
codecs=[BloscCodec(cname='zstd', clevel=5, shuffle='shuffle')]

# Optimal for speed
codecs=[BloscCodec(cname='lz4', clevel=1)]

# Optimal for compression ratio
codecs=[GzipCodec(level=9)]

Storage Backends

Zarr supports multiple storage backends through a flexible storage interface.

Local Filesystem (Default)

from zarr.storage import LocalStore

# Explicit store creation
store = LocalStore('data/my_array.zarr')
z = zarr.open_array(store=store, mode='w', shape=(1000, 1000), chunks=(100, 100))

# Or use string path (creates LocalStore automatically)
z = zarr.open_array('data/my_array.zarr', mode='w', shape=(1000, 1000),
                    chunks=(100, 100))

In-Memory Storage

from zarr.storage import MemoryStore

# Create in-memory store
store = MemoryStore()
z = zarr.open_array(store=store, mode='w', shape=(1000, 1000), chunks=(100, 100))

# Data exists only in memory, not persisted

ZIP File Storage

from zarr.storage import ZipStore

# Write to ZIP file
store = ZipStore('data.zip', mode='w')
z = zarr.open_array(store=store, mode='w', shape=(1000, 1000), chunks=(100, 100))
z[:] = np.random.random((1000, 1000))
store.close()  # IMPORTANT: Must close ZipStore

# Read from ZIP file
store = ZipStore('data.zip', mode='r')
z = zarr.open_array(store=store)
data = z[:]
store.close()

Cloud Storage (S3, GCS)

import s3fs
import zarr

# S3 storage
s3 = s3fs.S3FileSystem(anon=False)  # Use credentials
store = s3fs.S3Map(root='my-bucket/path/to/array.zarr', s3=s3)
z = zarr.open_array(store=store, mode='w', shape=(1000, 1000), chunks=(100, 100))
z[:] = data

# Google Cloud Storage
import gcsfs
gcs = gcsfs.GCSFileSystem(project='my-project')
store = gcsfs.GCSMap(root='my-bucket/path/to/array.zarr', gcs=gcs)
z = zarr.open_array(store=store, mode='w', shape=(1000, 1000), chunks=(100, 100))

Cloud Storage Best Practices:

Use consolidated metadata to reduce latency: zarr.consolidate_metadata(store)
Align chunk sizes with cloud object sizing (typically 5-100 MB optimal)
Enable parallel writes using Dask for large-scale data
Consider sharding to reduce number of objects

Groups and Hierarchies

Groups organize multiple arrays hierarchically, similar to directories or HDF5 groups.

Creating and Using Groups

# Create root group
root = zarr.group(store='data/hierarchy.zarr')

# Create sub-groups
temperature = root.create_group('temperature')
precipitation = root.create_group('precipitation')

# Create arrays within groups
temp_array = temperature.create_array(
    name='t2m',
    shape=(365, 720, 1440),
    chunks=(1, 720, 1440),
    dtype='f4'
)

precip_array = precipitation.create_array(
    name='prcp',
    shape=(365, 720, 1440),
    chunks=(1, 720, 1440),
    dtype='f4'
)

# Access using paths
array = root['temperature/t2m']

# Visualize hierarchy
print(root.tree())
# Output:
# /
#  ├── temperature
#  │   └── t2m (365, 720, 1440) f4
#  └── precipitation
#      └── prcp (365, 720, 1440) f4

H5py-Compatible API

Zarr provides an h5py-compatible interface for familiar HDF5 users:

# Create group with h5py-style methods
root = zarr.group('data.zarr')
dataset = root.create_dataset('my_data', shape=(1000, 1000), chunks=(100, 100),
                              dtype='f4')

# Access like h5py
grp = root.require_group('subgroup')
arr = grp.require_dataset('array', shape=(500, 500), chunks=(50, 50), dtype='i4')

Attributes and Metadata

Attach custom metadata to arrays and groups using attributes:

# Add attributes to array
z = zarr.zeros((1000, 1000), chunks=(100, 100))
z.attrs['description'] = 'Temperature data in Kelvin'
z.attrs['units'] = 'K'
z.attrs['created'] = '2024-01-15'
z.attrs['processing_version'] = 2.1

# Attributes are stored as JSON
print(z.attrs['units'])  # Output: K

# Add attributes to groups
root = zarr.group('data.zarr')
root.attrs['project'] = 'Climate Analysis'
root.attrs['institution'] = 'Research Institute'

# Attributes persist with the array/group
z2 = zarr.open('data.zarr')
print(z2.attrs['description'])

Important: Attributes must be JSON-serializable (strings, numbers, lists, dicts, booleans, null).

Integration with NumPy, Dask, and Xarray

NumPy Integration

Zarr arrays implement the NumPy array interface:

import numpy as np
import zarr

z = zarr.zeros((1000, 1000), chunks=(100, 100))

# Use NumPy functions directly
result = np.sum(z, axis=0)  # NumPy operates on Zarr array
mean = np.mean(z[:100, :100])

# Convert to NumPy array
numpy_array = z[:]  # Loads entire array into memory

Dask Integration

Dask provides lazy, parallel computation on Zarr arrays:

import dask.array as da
import zarr

# Create large Zarr array
z = zarr.open('data.zarr', mode='w', shape=(100000, 100000),
              chunks=(1000, 1000), dtype='f4')

# Load as Dask array (lazy, no data loaded)
dask_array = da.from_zarr('data.zarr')

# Perform computations (parallel, out-of-core)
result = dask_array.mean(axis=0).compute()  # Parallel computation

# Write Dask array to Zarr
large_array = da.random.random((100000, 100000), chunks=(1000, 1000))
da.to_zarr(large_array, 'output.zarr')

Benefits:

Process datasets larger than memory
Automatic parallel computation across chunks
Efficient I/O with chunked storage

Xarray Integration

Xarray provides labeled, multidimensional arrays with Zarr backend:

import xarray as xr
import zarr

# Open Zarr store as Xarray Dataset (lazy loading)
ds = xr.open_zarr('data.zarr')

# Dataset includes coordinates and metadata
print(ds)

# Access variables
temperature = ds['temperature']

# Perform labeled operations
subset = ds.sel(time='2024-01', lat=slice(30, 60))

# Write Xarray Dataset to Zarr
ds.to_zarr('output.zarr')

# Create from scratch with coordinates
ds = xr.Dataset(
    {
        'temperature': (['time', 'lat', 'lon'], data),
        'precipitation': (['time', 'lat', 'lon'], data2)
    },
    coords={
        'time': pd.date_range('2024-01-01', periods=365),
        'lat': np.arange(-90, 91, 1),
        'lon': np.arange(-180, 180, 1)
    }
)
ds.to_zarr('climate_data.zarr')

Benefits:

Named dimensions and coordinates
Label-based indexing and selection
Integration with pandas for time series
NetCDF-like interface familiar to climate/geospatial scientists

Parallel Computing and Synchronization

Thread-Safe Operations

from zarr import ThreadSynchronizer
import zarr

# For multi-threaded writes
synchronizer = ThreadSynchronizer()
z = zarr.open_array('data.zarr', mode='r+', shape=(10000, 10000),
                    chunks=(1000, 1000), synchronizer=synchronizer)

# Safe for concurrent writes from multiple threads
# (when writes don't span chunk boundaries)

Process-Safe Operations

from zarr import ProcessSynchronizer
import zarr

# For multi-process writes
synchronizer = ProcessSynchronizer('sync_data.sync')
z = zarr.open_array('data.zarr', mode='r+', shape=(10000, 10000),
                    chunks=(1000, 1000), synchronizer=synchronizer)

# Safe for concurrent writes from multiple processes

Note:

Concurrent reads require no synchronization
Synchronization only needed for writes that may span chunk boundaries
Each process/thread writing to separate chunks needs no synchronization

Consolidated Metadata

For hierarchical stores with many arrays, consolidate metadata into a single file to reduce I/O operations:

import zarr

# After creating arrays/groups
root = zarr.group('data.zarr')
# ... create multiple arrays/groups ...

# Consolidate metadata
zarr.consolidate_metadata('data.zarr')

# Open with consolidated metadata (faster, especially on cloud storage)
root = zarr.open_consolidated('data.zarr')

Benefits:

Reduces metadata read operations from N (one per array) to 1
Critical for cloud storage (reduces latency)
Speeds up tree() operations and group traversal

Cautions:

Metadata can become stale if arrays update without re-consolidation
Not suitable for frequently-updated datasets
Multi-writer scenarios may have inconsistent reads

Performance Optimization

Checklist for Optimal Performance

Chunk Size: Aim for 1-10 MB per chunk

# For float32: 1MB = 262,144 elements
chunks = (512, 512)  # 512×512×4 bytes = ~1MB

Chunk Shape: Align with access patterns

# Row-wise access → chunk spans columns: (small, large)
# Column-wise access → chunk spans rows: (large, small)
# Random access → balanced: (medium, medium)

Compression: Choose based on workload

# Interactive/fast: BloscCodec(cname='lz4')
# Balanced: BloscCodec(cname='zstd', clevel=5)
# Maximum compression: GzipCodec(level=9)

Storage Backend: Match to environment

# Local: LocalStore (default)
# Cloud: S3Map/GCSMap with consolidated metadata
# Temporary: MemoryStore

Sharding: Use for large-scale datasets

# When you have millions of small chunks
shards=(10*chunk_size, 10*chunk_size)

Parallel I/O: Use Dask for large operations

import dask.array as da
dask_array = da.from_zarr('data.zarr')
result = dask_array.compute(scheduler='threads', num_workers=8)

Profiling and Debugging

# Print detailed array information
print(z.info)

# Output includes:
# - Type, shape, chunks, dtype
# - Compression codec and level
# - Storage size (compressed vs uncompressed)
# - Storage location

# Check storage size
print(f"Compressed size: {z.nbytes_stored / 1e6:.2f} MB")
print(f"Uncompressed size: {z.nbytes / 1e6:.2f} MB")
print(f"Compression ratio: {z.nbytes / z.nbytes_stored:.2f}x")

Common Patterns and Best Practices

Pattern: Time Series Data

# Store time series with time as first dimension
# This allows efficient appending of new time steps
z = zarr.open('timeseries.zarr', mode='a',
              shape=(0, 720, 1440),  # Start with 0 time steps
              chunks=(1, 720, 1440),  # One time step per chunk
              dtype='f4')

# Append new time steps
new_data = np.random.random((1, 720, 1440))
z.append(new_data, axis=0)

Pattern: Large Matrix Operations

import dask.array as da

# Create large matrix in Zarr
z = zarr.open('matrix.zarr', mode='w',
              shape=(100000, 100000),
              chunks=(1000, 1000),
              dtype='f8')

# Use Dask for parallel computation
dask_z = da.from_zarr('matrix.zarr')
result = (dask_z @ dask_z.T).compute()  # Parallel matrix multiply

Pattern: Cloud-Native Workflow

import s3fs
import zarr

# Write to S3
s3 = s3fs.S3FileSystem()
store = s3fs.S3Map(root='s3://my-bucket/data.zarr', s3=s3)

# Create array with appropriate chunking for cloud
z = zarr.open_array(store=store, mode='w',
                    shape=(10000, 10000),
                    chunks=(500, 500),  # ~1MB chunks
                    dtype='f4')
z[:] = data

# Consolidate metadata for faster reads
zarr.consolidate_metadata(store)

# Read from S3 (anywhere, anytime)
store_read = s3fs.S3Map(root='s3://my-bucket/data.zarr', s3=s3)
z_read = zarr.open_consolidated(store_read)
subset = z_read[0:100, 0:100]

Pattern: Format Conversion

# HDF5 to Zarr
import h5py
import zarr

with h5py.File('data.h5', 'r') as h5:
    dataset = h5['dataset_name']
    z = zarr.array(dataset[:],
                   chunks=(1000, 1000),
                   store='data.zarr')

# NumPy to Zarr
import numpy as np
data = np.load('data.npy')
z = zarr.array(data, chunks='auto', store='data.zarr')

# Zarr to NetCDF (via Xarray)
import xarray as xr
ds = xr.open_zarr('data.zarr')
ds.to_netcdf('data.nc')

Common Issues and Solutions

Issue: Slow Performance

Diagnosis: Check chunk size and alignment

print(z.chunks)  # Are chunks appropriate size?
print(z.info)    # Check compression ratio

Solutions:

Increase chunk size to 1-10 MB
Align chunks with access pattern
Try different compression codecs
Use Dask for parallel operations

Issue: High Memory Usage

Cause: Loading entire array or large chunks into memory

Solutions:

# Don't load entire array
# Bad: data = z[:]
# Good: Process in chunks
for i in range(0, z.shape[0], 1000):
    chunk = z[i:i+1000, :]
    process(chunk)

# Or use Dask for automatic chunking
import dask.array as da
dask_z = da.from_zarr('data.zarr')
result = dask_z.mean().compute()  # Processes in chunks

Issue: Cloud Storage Latency

Solutions:

# 1. Consolidate metadata
zarr.consolidate_metadata(store)
z = zarr.open_consolidated(store)

# 2. Use appropriate chunk sizes (5-100 MB for cloud)
chunks = (2000, 2000)  # Larger chunks for cloud

# 3. Enable sharding
shards = (10000, 10000)  # Groups many chunks

Issue: Concurrent Write Conflicts

Solution: Use synchronizers or ensure non-overlapping writes

from zarr import ProcessSynchronizer

sync = ProcessSynchronizer('sync.sync')
z = zarr.open_array('data.zarr', mode='r+', synchronizer=sync)

# Or design workflow so each process writes to separate chunks

Additional Resources

For detailed API documentation, advanced usage, and the latest updates:

Official Documentation: https://zarr.readthedocs.io/
Zarr Specifications: https://zarr-specs.readthedocs.io/
GitHub Repository: https://github.com/zarr-developers/zarr-python
Community Chat: https://gitter.im/zarr-developers/community

Related Libraries:

Xarray: https://docs.xarray.dev/ (labeled arrays)
Dask: https://docs.dask.org/ (parallel computing)
NumCodecs: https://numcodecs.readthedocs.io/ (compression codecs)

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Zarr Python

Overview

Quick Start

Installation

Basic Array Creation

Core Operations

Creating Arrays

Opening Existing Arrays

Reading and Writing Data

Resizing and Appending

Chunking Strategies

Chunk Size Guidelines

Aligning Chunks with Access Patterns

Sharding for Large-Scale Storage

Compression

Configuring Compression

Compression Performance Tips

Storage Backends

Local Filesystem (Default)

In-Memory Storage

ZIP File Storage

Cloud Storage (S3, GCS)

Groups and Hierarchies

Creating and Using Groups

H5py-Compatible API

Attributes and Metadata

Integration with NumPy, Dask, and Xarray

NumPy Integration

Dask Integration

Xarray Integration

Parallel Computing and Synchronization

Thread-Safe Operations

Process-Safe Operations

Consolidated Metadata

Performance Optimization

Checklist for Optimal Performance

Profiling and Debugging

Common Patterns and Best Practices

Pattern: Time Series Data

Pattern: Large Matrix Operations

Pattern: Cloud-Native Workflow

Pattern: Format Conversion

Common Issues and Solutions

Issue: Slow Performance

Issue: High Memory Usage

Issue: Cloud Storage Latency

Issue: Concurrent Write Conflicts

Additional Resources

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