Namerror:name 'c' is not defined

Python Help
#1 
def get_gcd(a,b):
    global c
    global gcd 
    global rem 
    if a == 0:
        gcd =+ a 
    elif b == 0:
        gcd =+ b
    else:
        while a%b == 0 or b%a == 0:
            if a<b: 
                c =+ a // b 
                rem =+ a % b
            elif a > b:
                c =+ b //a
                rem =+ b % a
    gcd = c
    print(gcd)    

get_gcd(2,0)

what could be causing this error:

Traceback (most recent call last):
File “/home/naemmastae/Desktop/Python projects/ulamspiral.py”, line 20, in
get_gcd(2,0)
File “/home/naemmastae/Desktop/Python projects/ulamspiral.py”, line 17, in get_gcd
gcd = c
NameError: name ‘c’ is not defined

#2

The error is caused by c not being defined.

c is declared a global variable at the top of the function, but you still need to give it a value somewhere.

#3

okay please show me what you are saying in action

#4

It’s not clear what your script is dong, but as is, the else clause in your function will never run. so c will never have a value.

What’s does this script do?

#5

Trying to access an undefined global variable:

def myfunc():
    global a
    print(a)

myfunc()

Result:

Traceback (most recent call last):

  File ~/tmp/untitled2.py:6
    myfunc()

  File ~/tmp/untitled2.py:3 in myfunc
    print(a)

NameError: name 'a' is not defined

If you define the variable before running the function, it works:

def myfunc():
    global a
    print(a)


a = 1
myfunc()

Result:

1
#6

calculate gcd for two numbers

#7

Ah, right. I know it as Greatest Common Factor.

#8

c won’t have a value even if the else clause runs, because the += requires it to already be defined. The same NameError would still happen.

#9

Yes, ty. I get that – just trying to establish the logic.

#10

what if i’m to assign c to the result of an expression within the loop

#11

Define c outside the loop first, perhaps with the value 0, or some other initial value that makes sense for your application.

#12

The line gcd = c needs to be indented one more level so that it is lined up with the while ... line.

Your code uses =+ in six places. I don’t think that does what you are expecting. I think it is harmless though. Try removing the + sign.

Why do you have the three “global” lines?

#13

saw it somwhere as a solution to an error i had

#14

anyone who sees any error in my logic please dont hesitste to correct me im trying to find the hcf using the euclidean algorithm

#15

@Emma
Not too sure if I fully understand this, but does this do what you want?

def GCD(A, B):
    while A != 0 and B != 0:
        x, R = divmod(A, B)
        A = B
        B = R
    return A


A = 1024
B = 28

print(GCD(A, B))

I followed the principles from here: