Python Global Variables and Global Keyword

In this tutorial, you'll learn about global variables and the global keyword in Python. Global variables are variables that are accessible from any part of your code, unlike local variables, which are only accessible within the function or block of code where they are defined.

Global variables:

Global variables are defined outside of any function or block of code. They can be accessed and modified by any function in the program.

# Define a global variable
greeting = "Hello, World!"

def print_greeting():
    print(greeting)

# Call the function
print_greeting()  # Output: Hello, World!

In this example, we define a global variable greeting and use it inside the print_greeting function.

Local variables:

Local variables are defined within a function or block of code and are only accessible within that scope.

def print_greeting():
    # Define a local variable
    greeting = "Hello, World!"
    print(greeting)

# Call the function
print_greeting()  # Output: Hello, World!

In this example, we define a local variable greeting inside the print_greeting function.

Using the global keyword:

If you want to access and modify a global variable from within a function, you need to use the global keyword before the variable name.

# Define a global variable
greeting = "Hello, World!"

def change_greeting():
    global greeting  # Use the global variable
    greeting = "Hello, Python!"

# Call the function
change_greeting()
print(greeting)  # Output: Hello, Python!

In this example, we use the global keyword to access and modify the global variable greeting from within the change_greeting function.

Global variables in modules:

When you import a module, its global variables become accessible using the module's name as a prefix.

# my_module.py
greeting = "Hello, World!"

def print_greeting():
    print(greeting)

# main.py
import my_module

# Access the global variable from the module
print(my_module.greeting)  # Output: Hello, World!

# Call the function from the module
my_module.print_greeting()  # Output: Hello, World!

In this example, we define a global variable greeting and a function print_greeting in my_module.py. We then import my_module in main.py and access its global variable and function.

In this tutorial, you learned about global variables and the global keyword in Python. Global variables are useful for sharing data between different parts of your program, but you should use them judiciously to avoid making your code harder to understand and maintain.

Using global variables in Python:
- Description: Global variables are variables defined outside of any function or class, making them accessible globally in the entire script or module.
- Code:
```
global_variable = 10

def print_global_variable():
    print("Global Variable:", global_variable)

print_global_variable()
```

Python global keyword example:

Description: The global keyword is used to indicate that a variable is a global variable, allowing modification within functions.

Code:

global_variable = 10

def modify_global_variable():
    global global_variable
    global_variable += 5

modify_global_variable()
print("Modified Global Variable:", global_variable)

Global variables in nested functions Python:

Description: Global variables can be accessed in nested functions, but modifying them requires the global keyword.

Code:

global_variable = 10

def outer_function():
    global_variable = 5  # This creates a new local variable
    
    def inner_function():
        nonlocal global_variable
        global_variable += 2

    inner_function()
    print("Modified Global Variable in Nested Function:", global_variable)

outer_function()