NAstuden NAstuden - 1 year ago 215
Python Question

While-loop: UnboundLocalError: local variable referenced before assignment

I'm using python 3.5.

So I'm trying to create a function that takes x and y as positive float input, and then computes and returns R = x - N * y, where N is the largest integer, so that x > N * y.

I made this function:

def floatme(x,y):

N = 1

while x <= N * y:
R = x - N * y
N = N+1

return R

but then I receive the following error, when running my function:

UnboundLocalError: local variable 'R' referenced before assignment

I searched around and found that this happens when an assigned variable in the function, is already assigned outside of it. But this is not the case for my function, so I do not understand why Python is complaining?

Answer Source

R is defined inside the while loop. If the condition of the while loop is not true initially, its body never executes and R is never defined. Then it is an error to try to return R.

To solve the problem, initialize R to something before entering the loop.

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