Defining Functions

Functions are reusable blocks of code that perform a specific task. You define a function using the def keyword.

Syntax: 

  def function_name(parameters):
    # code block
    return value  # optional

Example: 

  def greet(name):
    return f"Hello, {name}!"

print(greet("Alice"))

Function Arguments and Return Values

  • Arguments: Inputs to the function, specified within the parentheses when the function is called.
    • Positional Arguments: Arguments passed to the function in the correct order.
    • Keyword Arguments: Arguments passed with the name of the parameter.
    • Default Arguments: Arguments that assume a default value if a value is not provided.

Example: 

  def add(a, b=5):
    return a + b

print(add(3))        # Uses default value for b
print(add(3, 7))     # Overrides default value
  • Return Values: The value that a function sends back to the caller using the return statement. If no return statement is used, the function returns None by default.

Example: 

  def multiply(a, b):
    return a * b

result = multiply(2, 3)

Lambda Functions

Lambda functions are small anonymous functions defined using the lambda keyword. They can have any number of arguments but only one expression.

Syntax: 

  lambda arguments: expression

Example: 

  add = lambda x, y: x + y
print(add(3, 5))

Importing Modules

Modules are files containing Python code that can be imported into your script to reuse functions, variables, and classes.

  • Importing a Module:
  import module_name
  • Importing Specific Functions:
  from module_name import function_name
  • Importing with an Alias:
  import module_name as alias

Example: 

  import math

print(math.sqrt(16))

from math import pi
print(pi)

Standard Library Overview

Python’s standard library is a collection of modules and packages that come with Python, providing various functionalities out of the box.

  • Common Modules:
    • os: Operating system interfaces.
    • sys: System-specific parameters and functions.
    • math: Mathematical functions.
    • datetime: Date and time manipulation.
    • random: Random number generation.
    • json: JSON serialization and deserialization.

Example: 

  import datetime

today = datetime.date.today()
print("Today's date:", today)

Let me know if you need more details or specific examples!