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Using Python Help Mode and the help() Function

Learn to use Python's built-in help() function and interactive help mode to explore topics, modules, functions, classes, methods, and attributes.

Python includes a built-in documentation system that you can use directly from the interactive interpreter. The main entry point is help(), which is powered by Python's pydoc documentation mechanism.

A REPL (read-evaluate-print loop) is Python's interactive interpreter. It normally displays the >>> prompt, accepts an expression or command, evaluates it, and displays the result.

The help system is useful when you need a quick reference for unfamiliar code. It can use documentation text, object signatures, docstrings, and module metadata. A docstring is documentation text attached to a module, class, function, or method.

Start Python and enter help mode

Open a terminal or command prompt and start Python:

python

Depending on your installation, the command may be named differently, such as python3. When Python starts, you should see the normal interpreter prompt:

>>>

Call help() without an argument:

>>> help()

Python displays introductory instructions and changes the prompt to:

help>

This is the interactive help utility: a prompt-driven documentation browser separate from the normal Python prompt. At a conceptual level, its instructions tell you that you can enter a module, keyword, topic, or object name, and that commands such as topics, keywords, symbols, and modules help you discover available documentation.

Navigate the interactive help prompt

At the help> prompt, enter the name you want to investigate. You can request a module, a keyword, a language topic, or a dotted name such as a module attribute.

help> sys
help> NUMBERS
help> if
help> sys.platform

Built-in language topics commonly appear in uppercase. Use the spelling and capitalization shown by the help utility, rather than guessing a topic name.

Interactive Help Prompt Commands

Input at help> — Purpose — Example use

topics — List recognized language topics — help> topics

keywords — List Python syntax keywords and show their documentation names — help> keywords

symbols — List special symbols and punctuation-related help entries — help> symbols

modules — List importable modules discovered in the environment — help> modules

modules <search text> — Filter the module search by text — help> modules json

A topic name — Read a language concept — help> NUMBERS

A module or dotted name — Read module or attribute documentation — help> sys or help> sys.platform

quit — Leave help mode and return to the Python prompt — help> quit

To leave the utility, enter quit:

help> quit
>>>

The >>> prompt confirms that you are back in the normal REPL.

Browse language topics

A topic is a named help category describing a Python language concept. Topics are not the same as values in your program. For example, NUMBERS documents how numeric literals and related numeric concepts work; it does not describe one particular number stored in a variable.

>>> help()
help> topics
help> NUMBERS

The NUMBERS topic can help you understand numeric literals, which are source-code representations of numbers. Examples include integer literals such as 42, floating-point literals such as 3.14, and imaginary-number forms such as 2j.

While reading the topic, you may see references to related subjects, including:

  • INTEGER for integer behavior and literals
  • FLOAT for floating-point values
  • COMPLEX for complex numbers
  • TYPES for Python's object and type model

Use topics first when you are unsure which topic names are available:

help> topics

Look up modules and their contents

A module is a Python file or importable package namespace containing code and objects. The standard-library sys module provides information and operations related to the Python interpreter.

help> sys

A module lookup generally shows a summary, documented functions, classes, data values, and other contents. The exact sections and wording depend on the Python release.

You can request an attribute with dot notation:

help> sys.platform

An attribute is a named value associated with a module, class, or object. sys.platform is a string attribute that identifies the platform on which Python is running.

To search for installed modules, use modules:

help> modules
help> modules json

The unfiltered command can be slow because it searches many importable packages. A search term narrows the output. Some environments may also display import-related messages while scanning modules.

Inspect functions, classes, methods, and attributes

You can pass a Python object directly to help(). These examples run at the normal >>> prompt:

>>> help(len)
>>> help(str)
>>> help(list.append)

help(len) documents a built-in function. help(str) documents the built-in string type, including its behavior and methods. help(list.append) focuses on the append method belonging to lists.

For a module attribute, import the module before using a Python expression that refers to it:

>>> import sys
>>> help(sys.platform)

Without import sys, the name sys does not exist in the current interpreter session. A string lookup can sometimes avoid that requirement:

>>> help('sys')
>>> help('sys.platform')

There is an important distinction between the value of an attribute and its documentation. When sys.platform is evaluated, it produces a platform identifier such as a string. When passed to help(), Python may mainly display documentation for the object's type, str, rather than explain the platform-specific meaning of that particular value.

>>> import sys
>>> sys.platform
'...'
>>> type(sys.platform)
<class 'str'>

Use help(sys) for the module's documented attributes and consult the official library documentation when you need the exact meaning of sys.platform.

Direct help calls and help mode

Direct help() Calls Compared with Help Mode

Approach — Example — Best use case — Requirements

Interactive help utility via help() — help(), then help> sys — Exploring when you do not yet know the target — Start from the normal REPL; leave with quit

Direct object lookup via help(object) — help(len) or help(list.append) — Quickly documenting a known object — The object must be available in the current session

String-based lookup via help('name') — help('sys') or help('sys.platform') — Looking up a module or dotted name without first binding it as a Python name — The string must identify a recognized topic, module, or object name

Direct calls are usually quicker when you already know what you need. Help mode is better for discovery because it provides commands for finding topics, keywords, symbols, and modules.

Read and interpret help output

When help displays an object, look for these parts:

  • Object kind: whether the target is a function, class, method, module, type, or another object.
  • Call signature: the parameters accepted by a function, method, or class constructor.
  • Description: summary text from documentation or a docstring.
  • Methods and attributes: operations and named values provided by a class or module.
  • Related topics: other concepts or objects that may help explain the target.

For example, a function entry may show a signature and a short description, while a class entry may include its constructor, methods, inherited members, and data attributes.

Signatures and wording can vary between Python releases. Documentation can also vary by installed package version, so do not assume that every line will look identical on another computer.

Long output may open in a pager, a tool that displays text one screen at a time. Follow the controls shown by your environment. Often a pager uses a key such as q to exit, but the on-screen instructions take precedence. After leaving the pager, you may still need to enter quit at the help> prompt.

Troubleshoot common problems

Using help without parentheses

help is a function. Entering its name alone does not start the utility and may produce a name-related result or error in some contexts.

>>> help()
>>> help(len)

Using an unimported module

This direct lookup requires an import:

>>> help(sys.platform)
NameError: name 'sys' is not defined

Import the module first, or use a string-based lookup:

>>> import sys
>>> help(sys.platform)

>>> help('sys.platform')

Seeing string documentation for sys.platform

This is expected when the target is a string-valued attribute. Evaluate sys.platform to see its current value, use type(sys.platform) to identify its type, and use help(sys) or official library documentation for the attribute's semantics.

Topic not found

The name may not be a built-in topic, or it may have the wrong spelling or capitalization. Enter topics and use a recognized name exactly as listed.

Module search is slow

modules searches installed importable packages, which can be numerous and may behave differently across environments. Use a narrow command such as modules json, or consult the package documentation directly.

Unable to return to the REPL

The help utility remains active until you explicitly leave it. Enter quit at help>. If a pager is currently visible, exit the pager using its displayed control first.

Third-party help is sparse

Undocumented third-party code may contain few docstrings or little documentation metadata. In that case, use the package's official documentation, source code, or installed documentation resources.

Scope and limitations

Built-in help is excellent for quick reference and discovery, especially while exploring unfamiliar modules or objects. It is not guaranteed to provide a complete tutorial or a detailed explanation of every value.

If a package has limited docstrings or metadata, help() may produce little useful information. For extended tutorials, examples, configuration guidance, and version-specific details, use the official Python library documentation or the package's official documentation.

For related exploration, see Python help mode, and practice combining help() with imports, dot notation, type(), and object inspection.