“global” Keyword in Python: Accessing Variables Outside of Functions

"global" Keyword in Python: Accessing Variables Outside of Functions

In Python, variables can have either local or global scope, which means that they can either be accessed only within the function where they are defined or they can be accessed from anywhere in the program, respectively. The global keyword is used to access variables outside of functions.

Local vs Global Variables

Before we dive deeper into the global keyword, let’s first understand the difference between local and global variables.

Local Variables

A local variable is a variable that is defined inside a function. It can be accessed only within that function. If you try to access it outside the function, you will get a NameError.

def my_function():
    x = 1
    print(x)

my_function()
print(x)

Output:

1
NameError: name 'x' is not defined

In the above example, x is a local variable. It is defined inside the my_function() function and can be accessed only within the function.

Global Variables

A global variable, on the other hand, is a variable that is defined outside of any function. It can be accessed from anywhere in the program.

x = 2

def my_function():
    print(x)

my_function()
print(x)

Output:

2
2

In the above example, x is a global variable. It is defined outside of the my_function() function and can be accessed from within the function as well as outside the function.

The Global Keyword

Sometimes, you may want to access a global variable from within a function, or you may want to modify the value of a global variable from within a function. For this, you can use the global keyword.

Accessing a Global Variable from Within a Function

To access a global variable from within a function, you need to use the global keyword followed by the name of the variable.

x = 3

def my_function():
    global x
    print(x)

my_function()
print(x)

Output:

3
3

In the above example, we have used the global keyword to access the global variable x from within the my_function() function.

Modifying a Global Variable from Within a Function

To modify the value of a global variable from within a function, you also need to use the global keyword.

x = 4

def my_function():
    global x
    x = 5

my_function()
print(x)

Output:

5

In the above example, we have used the global keyword to modify the value of the global variable x from within the my_function() function.

Why the Global Keyword is Important

Using the global keyword can be very helpful in certain situations, but you should use it carefully. If you use it too much, it can make your code hard to read and debug. It’s often better to pass variables as parameters or to return values from functions.

Here’s an example of how using the global keyword too much can make your code more complex:

x = 6

def my_function():
    global x
    y = x + 1
    global z
    z = y + 1

my_function()
print(x)
print(z)

Output:

6
8

In the above example, we have used the global keyword to access the global variable x and to modify the global variable z from within the my_function() function. This makes the function harder to understand and to modify.

Conclusion

The global keyword is a powerful tool that allows you to access and modify global variables from within functions. However, you should use it sparingly and try to keep your code organized and easy to read.

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