Help with code -> global declaration

Question

Hi, I have the following piece of code:
#Create a function that intakes a simple arithmetic calculation and produces the answer

import operator
ops={'+':operator.add,'-':operator.sub,'*':operator.mul,'/':operator.truediv}
q_calc=str(input())
def calculator(calculation):
l_calc=list(calculation)
for num in range(0,len(calculation)-1):
if l_calc[num]=='+' or l_calc[num]=='-' or l_calc[num]=='/' or l_calc[num]=='*':
num1=l_calc[:num-1]
num2=l_calc[num+1:]
num1=''.join(num1)
num2=''.join(num2)
num1=int(num1)
num2=int(num2)
change=l_calc[num]
change=str(''.join(change))
else:
print()
global change
print(ops[change](num1,num2))
calculator(q_calc)

This creates a calculator that can do simple operations. However, when it comes to running the code, the following message appears: 'SyntaxWarning: name 'change' is assigned to before global declaration'. This is referencing the line before the penultimate line of code. Please can I have some help in how to fix this and what has gone wrong.

Answer 1

You could just put
change = None
before the for loop without the global and this should take care of the UnboundLocalError that you shouldn't be getting anyway, unless there is more to your code that we aren't privy to.

Answer 2

You don't need the
global change
line. change is in the same scope.
You're getting the error because you're assigning change in the if statement prior to making it global within the same scope. I don't see any need to make change global. Remove the line and your code will run. You may still have some other issues (logic) with your code, but it will run.

Answer 3

It runs in the playground ok with the line commented out.

https://code.sololearn.com/c3esPxpuDObQ/?ref=app

Answer 4

I was getting UnboundLocalError without the global however, so it is needed, unless there is another way to prevent the error

Answer 5

Make your Declaration here:

def calculator(calculation):
global change
change = ""
l_calc=list(calculation)
....

But you should NOT use global variables.