Python - Global Variables

In Python, a global variable is a variable that is declared outside of any function and can be accessed by any function in the same module or file. Global variables can be useful for storing values that are needed by multiple functions within the same module or file.

In Python, declaring a variable outside of any function is all that's needed to create a global variable:

```

# defining a global variable

my_global_var = "Hello World"

# Creating a function that utilizes the global variable:

def print_global_var():

    print(my_global_var)

# calling the function

print_global_var()  # output: "Hello World"

```

In the example above, `my_global_var` is a global variable that can be accessed by the function `print_global_var()` because it is defined outside of any function.

It is also possible to modify the value of a global variable from within a function using the `global` keyword:

```

# defining a global variable

my_global_var = "Hello World"

# defining a function that modifies the global variable

def modify_global_var():

    global my_global_var

    my_global_var = "Goodbye World"

# calling the function

modify_global_var()

# printing the modified global variable

print(my_global_var)  # output: "Goodbye World"

```

In the example above, the `modify_global_var()` function modifies the value of `my_global_var` using the `global` keyword, which allows the function to access and modify the global variable.

However, it is generally not recommended to use global variables excessively as they can make code harder to read and debug, especially in larger projects. It is often better to use function arguments and return values to pass data between functions.