Python Keyword Reference
A quick reference for Python keywords, functions, and objects. Find what you need to build powerful applications.
The `def` Keyword
The def keyword is used to create, or define, a function in Python. Functions are reusable blocks of code that perform a specific action.
Functions are central to writing clean, modular, and efficient Python code. They help break down large programs into smaller, manageable pieces.
Example
my_functions.py
# Function definition
def greet(name):
"""This function greets the person passed in as a parameter"""
return "Hello, " + name + "!"
# Calling the function
print(greet("World")) # Output: Hello, World!
# Function with a default argument
def say_hello(name="User"):
return "Hello, " + name
print(say_hello()) # Output: Hello, User
print(say_hello("Alice")) # Output: Hello, Alice
Syntax
Basic syntax for defining a function:
| Syntax | Description |
|---|---|
| def function_name(parameters): | Defines a function with a name and optional parameters. |
| """docstring""" | An optional string to document the function's purpose. |
| # code block | The indented block of code that runs when the function is called. |
| return [expression] | Exits the function and optionally passes back a value. |