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help() Function Complexity

The help() function displays documentation for Python objects, modules, and topics.

Complexity Analysis

Operation Time Space Notes
Get docstring O(1) O(m) m = docstring length
Format help text O(m) O(m) m = documentation size
Display help O(m) O(m) I/O operation
Introspect object O(n) O(n) n = number of attributes

Basic Usage

Help for Objects

# O(m) - retrieve and display docstring
help(str)              # Help for str class
help(list.append)      # Help for list.append method
help(42)               # Help for int
help("hello")          # Help for str instance

Interactive Mode

# O(m) - enter pager for documentation
# In interactive Python shell:
help()  # Enter help system
# Type module name or function name for help

# Type 'quit' to exit help system

Help for Modules

import os
# O(n) - introspect module
help(os)  # Shows module docstring and all members
help(os.path)  # Help for specific submodule

Complexity Details

Docstring Retrieval

# O(m) - m = docstring length
def my_function():
    """This is documentation."""
    pass

# Retrieve docstring
doc = my_function.__doc__  # O(1)

# help() formats and displays it - O(m)
help(my_function)

Object Introspection

# O(n) - where n = number of members
# help() uses dir() and getattr() internally

class MyClass:
    attribute1 = 10
    attribute2 = 20

    def method1(self):
        """First method."""
        pass

    def method2(self):
        """Second method."""
        pass

# help() will introspect all members
help(MyClass)  # O(n) - n = 4 members

Performance Patterns

vs Manual Inspection

# help() is comprehensive but slow
help(str)  # O(n) - introspects everything

# vs direct access (fast)
print(str.__doc__)  # O(1) - just docstring

# For performance-critical code, use direct access
# For interactive exploration, use help()

Common Use Cases

Interactive Exploration

# In Python interpreter
# O(m) - displays formatted help

help(list)
# Shows all list methods and documentation

help(list.sort)
# Shows help for specific method

help()
# Interactive help mode

Module Discovery

# O(n) - explore module contents
import json

help(json)  # Show all JSON module functions

# Or get quick summary
import pydoc
pydoc.getdoc(json)  # O(n) - get formatted docs

Method Signatures

# O(m) - get signature information
help(str.format)
# Shows parameters, return value, examples

# vs inspect module (more detailed)
import inspect
sig = inspect.signature(str.format)
# O(m) - get signature object

Alternatives

Direct Attribute Access

# O(1) - faster, but less formatted
obj = [1, 2, 3]
docstring = obj.__doc__

# vs help
help(obj)  # O(m) - slower but formatted

pydoc Module

import pydoc

# O(n) - more control
docs = pydoc.getdoc(str)  # Get formatted documentation
pydoc.render_doc(str)     # Get as HTML

# Server mode - browse documentation
pydoc.start_server(port=8000)

inspect Module

import inspect

# O(1) - fast attribute access
signature = inspect.signature(my_func)
source = inspect.getsource(my_func)
members = inspect.getmembers(obj)  # O(n)

# More programmatic than help()

Interactive Help System

# help() without arguments
# Starts interactive help system

# help()
# Then type:
# >>> list.append    (shows help for list.append)
# >>> modules        (shows all available modules)
# >>> keywords       (shows Python keywords)
# >>> topics         (shows special topics)
# >>> quit           (exits help)

Practical Examples

Documentation Lookup

# O(m) - find how to use a function
def understand_function(func):
    help(func)

# Examples:
understand_function(len)
understand_function(str.split)
understand_function(dict.get)

Debugging Unknown Objects

# O(n) - understand what you're working with
def analyze(obj):
    print(f"Type: {type(obj)}")
    help(obj)  # See what methods available
    print(f"Dir: {dir(obj)}")

data = {"key": "value"}
analyze(data)  # Shows dict documentation

Learning Python Features

# O(m) - look up language features
help("if")      # Help on if statement
help("for")     # Help on for loops
help("class")   # Help on class definition
help("print")   # Help on print function

Performance Considerations

Startup Time

# help() can be slow on first call (module imports)
import time

start = time.time()
help(str)  # First call slower
first = time.time() - start

start = time.time()
help(int)  # Subsequent calls faster (modules cached)
second = time.time() - start

# second < first (due to module caching)

vs Inline Documentation

# For frequently called functions, cache docs
HELP_CACHE = {}

def get_help(obj):
    key = id(obj)
    if key not in HELP_CACHE:
        HELP_CACHE[key] = obj.__doc__  # O(1)
    return HELP_CACHE[key]

# Faster than calling help() repeatedly

Advanced Usage

Programmatic Documentation Access

# O(m) - get docs without printing
import pydoc

docs = pydoc.render_doc(str, title="String Documentation")
# Returns formatted HTML string

# Use in web server, etc.

Documentation Server

import pydoc

# Start local documentation server
# pydoc.start_server(port=8000)
# Then visit http://localhost:8000

# Or generate HTML
pydoc.writedoc(str, outdir="/tmp/docs")
# Creates HTML documentation file

Edge Cases

Objects Without Docstrings

# O(1) - returns "no documentation"
class Empty:
    pass

help(Empty)  # "no documentation available"

Built-in C Objects

# O(m) - limited docstrings for C objects
help(len)  # C function, limited help
help(dict)  # Built-in type, has docstring

Lambda Functions

# O(1) - minimal help
func = lambda x: x ** 2
help(func)  # Shows minimal info (no docstring)

# Add docstring
func.__doc__ = "Square a number"
help(func)  # Shows custom docstring

Best Practices

✅ Do:

  • Use help() for interactive exploration
  • Use help(topic) to learn about Python features
  • Check __doc__ attribute directly in code
  • Use inspect module for programmatic access
  • Write clear docstrings for your functions

❌ Avoid:

  • Using help() in tight loops (call once, cache result)
  • Assuming help() output format is stable
  • Using help() for production code (direct access faster)
  • Forgetting to write docstrings
  • dir() - List object attributes
  • callable() - Check if object is callable
  • type() - Get object type
  • inspect - Advanced introspection

Version Notes

  • Python 2.x: help() available in interactive mode
  • Python 3.x: Same functionality, improved formatting
  • All versions: Works on all objects with __doc__ attribute