Python Global Variables: How Do They Differ From the Local Ones?

The difference between local and global variables in Python

In the example below, you can see two variables declared – bit and bdg:

def f():
    bit = "BitDegree"
    print (bit)
f()

bdg = "BitDegree"
print (bdg)

While both have the same value assigned, they are declared and used differently:

• bit is declared within the function. This makes it a local variable. Its scope is the body of the function – it cannot be used anywhere else.
• bdg is declared outside of the function – this makes it global. You can use Python global variables anywhere in the code.

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How to use global variables in Python

When declaring global variables in Python, you can use the same names you have already used for local variables in the same code – this will not cause any issues because of the scope difference:

• If you use the variable within the function, it will prefer the local variable by default:
Example Copy

pizza = "Pepperoni"
def f():
    pizza = "Hawaii"
    print (pizza)

f()

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• If you use the variable anywhere else in the code, you will get the value of the global variable:
Example Copy

pizza = "Pepperoni"
def f():
    pizza = "Hawaii"

print (pizza)

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You can also create local variables by modifying previously defined Python global variables inside the function by using the keyword global:

bdg = 1000

def f():
    global bdg
    bdg = bdg + 500

Python global variables: useful tips

• You can change the value of a Python global variable by simply assigning it a new value (redeclaring).
• To delete a variable, use the keyword del. Trying to use a deleted variable will cause an error to fire.