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Python global variable

Global variables are a fundamental concept in Python programming, allowing data to be accessed and modified throughout an entire script or module

What is a Global Variable?

A global variable is a variable that is defined outside of any function or block and can be accessed from any part of the program. Global variables are useful when you need to share data across multiple functions without passing them as parameters.

python global variable with example

In the example above, global_var is a global variable defined outside of any function and is accessible within the display_global function.

Characteristics of Global Variables

Understanding the characteristics of global variables is crucial for effective programming. Here are some key features:

  1. Global Scope: Global variables can be accessed from anywhere within the module, including inside functions.

  2. Persistent Lifetime: Global variables exist for the duration of the program. They are created when the program starts and are destroyed when the program ends.

  3. Shared Data: Global variables allow for sharing data between functions, which can simplify data management in larger programs.

  4. Potential for Side Effects: Modifying global variables can lead to unintended side effects, making debugging difficult.

Defining Global Variables

Global variables are defined simply by assigning a value to a name outside of any function.

Syntax

Accessing Global Variables

Global variables can be accessed in any function without needing to declare them as global unless you intend to modify them. Here’s how you can access global variables.

Example

Modifying Global Variables

To modify a global variable within a function, you must declare it as global using the global keyword. This informs Python that you intend to use the variable defined in the global scope.

Example