Python Variable Scope Examples

Python Variable Scope Examples

a = 1

def foo():
    print(a)     # Prints 1. Accesses the variable a outside its own scope.

foo()
print(a)         # Prints 1. a not modified.

b = 2
def bar():
    b = 3        # Creates a new variable b within the function scope.
    print(b)     # Prints 3. Accesses the variable within its own scope.

bar() 
print(b)         # Prints 2. Printing the variable in the global scope.
    
c = 3
def foobar():
    c = c + 1    # UnboundLocalError: local variable 'c' referenced before assignment.
                 # Python treats this like d = d + 1; it is unable to find d in the scope.
    print(c)          

foobar()         # Comment out this line to skip the crash.

d = 4
def barfoo():
    global d     # Cannot use nonlocal d. nonlocal only accesses parent function variables. 
                 # For barfoo, there is no parent function.
    d = 5        # Modifies the global variable d
    print(d)     # Prints 5. Local variable d is the same as the one in the global scope.

barfoo()         
print(d)         # Prints 5. Global variable d was modified within barfoo()

def outer():
    e = 5
    def inner():
        nonlocal e    # Can use nonlocal now to refer to variable in the parent function.
        e += 1        
        print(e)
    return inner

in_test = outer()
in_test()           # Prints 6.
in_test()           # Prints 7.