Question

Ok, the below code is completely scrap, pointless code I made up; but I find it weird that I can access the variable “b” from the qwerty() function while b was only declared inside while… I thought I could only access it if I declared it globally somehow?

x = 14
while (x > 10):
    b = 3
    b += 3
    print(b)
    x -= 1

def qwerty():
    if b == 6:
         print("b can be accessed elsewhere?")

input("")

Running this code, “b can be accessed elsewhere?” will be printed… even though b == 6 is referencing the variable b that was declared in the separate while() function.

I guess I am still confused about the properties of global and local variables in python. Can anyone explain why the above happens?

Answer 1

while is not a function. The only constructs that create their own scopes are def, class, and generator expressions / comprehensions (depending on version).

if True:
    while 1:
        for x in range(1):
            z = 1
        break

def function():
    print(z)

function() # prints 1

This works almost the same way as inside functions.

def function():
    while True:
        x = 5
        break
    def nested():
        print(x)
    nested() # prints 5
    x = 10
    nested() # prints 10

I say almost because there are a few subtle differences in how you can modify outer variables depending on whether they are global or belong to an enclosing function.