Python Functions and Data Types

Functions

• Definition: A function is a block of code that performs a specific task and can be reused.

• Syntax:

  def function_name(parameters):
      # code block
      return value
  

• Parameters:

  • Input values for the function.
  • Can be optional (default values) or required.

• Return Statement:

  • Returns a value from the function to the caller.
  • If no return statement is provided, the function returns None.

• Types of Functions:

  • Built-in Functions: Predefined functions (e.g., print(), len(), type()).
  • User-defined Functions: Created by users to perform specific tasks.
  • Lambda Functions: Anonymous functions defined with the lambda keyword for short operations.

• Scope:

  • Local Scope: Variables defined inside a function.
  • Global Scope: Variables defined outside of all functions, accessible within functions using the global keyword.

Data Types

• Basic Data Types:

  • Integer (int): Whole numbers (e.g., 5, -3).
  • Float (float): Decimal numbers (e.g., 3.14, -0.001).
  • String (str): Sequence of characters (e.g., "Hello, World!").
  • Boolean (bool): Represents True or False.

• Data Structures:

  • List: Ordered, mutable collection (e.g., [1, 2, 3]).
  • Tuple: Ordered, immutable collection (e.g., (1, 2, 3)).
  • Set: Unordered collection of unique elements (e.g., {1, 2, 3}).
  • Dictionary (dict): Collection of key-value pairs (e.g., {"key": "value"}).

• Type Conversion:

  • Convert between types using functions like int(), float(), str(), etc.

• Type Checking:

  • Use type() to check the data type of a variable.
  • Use isinstance() to check if a variable belongs to a specific type.

Functions

• A function is a reusable block of code designed to perform specific tasks.
• Function syntax in Python follows the format:

  def function_name(parameters):
      # code block
      return value
  

• Functions can have parameters, which can either be mandatory or have default values.
• The return statement in a function sends a value back to the caller; lacking a return statement results in returning None.
• Types of functions include:
  • Built-in Functions: Predefined functionalities such as print(), len(), and type().
  • User-defined Functions: Functions created by users for specific tasks.
  • Lambda Functions: Short, anonymous functions created with the lambda keyword for quick operations.
• Scope refers to variable accessibility:
  • Local Scope: Variables defined within a function, restricted to that function's context.
  • Global Scope: Variables defined outside functions, accessible inside functions with the global keyword.

Data Types

• Basic data types in Python include:
  • Integer (int): Represents whole numbers like 5 or -3.
  • Float (float): Represents decimal numbers like 3.14 or -0.001.
  • String (str): A sequence of characters, e.g., "Hello, World!".
  • Boolean (bool): Represents two values, True or False.
• Common data structures include:
  • List: An ordered and mutable collection of elements, e.g., [1, 2, 3].
  • Tuple: An ordered and immutable collection, e.g., (1, 2, 3).
  • Set: An unordered collection of unique elements, e.g., {1, 2, 3}.
  • Dictionary (dict): A collection of key-value pairs, e.g., {"key": "value"}.
• Type Conversion: Transform data types using functions like int(), float(), and str().
• Type Checking:
  • Use type() to determine a variable's data type.
  • Use isinstance() to check if a variable is a specific type.