Python Global, Local and Nonlocal variables

In this tutorial, you’ll find out about Python Global variables, Local variables, Nonlocal variables, and where to use them.

Global Variables

In Python, a variable pronounced outside of the capacity or in worldwide extension is known as a global variable. This implies a global variable can be gotten to inside or outside of the function.

Let’s see an example of how a global variable is created in Python.

Example 1: Create a Global Variable

x = "global"

def foo():
    print("x inside:", x)


foo()
print("x outside:", x)

Output

x inside: global
x outside: global

In the above code, we created x as a global variable and defined a foo() to print the global variable x. Finally, we call the foo() which will print the value of x.

What if you want to change the value of x inside a function?

x = "global"

def foo():
    x = x * 2
    print(x)

foo()

Output

UnboundLocalError: local variable 'x' referenced before assignment

The output shows an error since Python treats x as a local variable and x is also not characterized inside foo().

To make this work, we use the global keyword.  Visit the Python Global Keyword to learn more.

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Local Variables

A variable declared inside the capacity’s body or in the neighborhood degree is known as a local variable.

Example 2: Accessing local variable outside the scope

def foo():
    y = "local"


foo()
print(y)

Output

NameError: name 'y' is not defined

The output shows an error because we are trying to access a local variable y in a global scope whereas the local variable only works inside foo() or local scope.

How about we see a model on how a local variable is made in Python.

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Model 3: Create a Local Variable

Ordinarily, we declare a variable inside the function to make a local variable.

def foo():
    y = "local"
    print(y)

foo()

Output

local

Let’s take a look at the earlier problem where x was a global variable and we wanted to modify x inside foo().

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Global and local variables

Here, we will show how to use global variables and local variables in the same code.

Example 4: Using Global and Local variables in the same code

x = "global "

def foo():
    global x
    y = "local"
    x = x * 2
    print(x)
    print(y)

foo()

Output

global global 
local

In the above code, we declare x as a worldwide and y as a neighborhood variable in the foo(). At that point, we use augmentation administrator * to adjust the global variable x and we print both x and y.

In the wake of calling the foo(), the estimation of x becomes worldwide in light of the fact that we utilized the x * 2 to print two times worldwide. From that point forward, we print the estimation of neighborhood variable y i.e local.

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Example 5: Global variable and Local variable with the same name

x = 5

def foo():
    x = 10
    print("local x:", x)


foo()
print("global x:", x)

Output

local x: 10
global x: 5

In the above code, we used a similar name x for both worldwide variable and local variable. We get an alternate outcome when we print a similar variable in light of the fact that the variable is pronounced in the two extensions, for example, the neighborhood scope inside foo() and worldwide degree outside foo().

When we print the variable inside foo(), it yields nearby x: 10. This is known as the nearby extent of the variable.

Also, when we print the variable outside the foo(), it yields worldwide x: 5. This is known as the global scope of the variable.

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Nonlocal Variables

Nonlocal variables are used in nested functions whose local scope isn’t characterized. This implies the variable can be neither in the local nor the global scope.

Let’s see an example of how a global variable is created in Python.

We use nonlocal keywords to create nonlocal variables.

Example 6: Create a nonlocal variable

def outer():
    x = "local"

    def inner():
        nonlocal x
        x = "nonlocal"
        print("inner:", x)

    inner()
    print("outer:", x)


outer()

Output

inner: nonlocal
outer: nonlocal

In the above code, there is a nested inner() function. We use nonlocal keywords to create a nonlocal variable. The inner() function is defined in the scope of another function outer().

Note: If we change the value of a nonlocal variable, the changes appear in the local variable.

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