Answer 1

The only solution is to retype the because sometimes the character has some hidden special characters in it, mostly from internet examples:

By the way, I've noticed some bugs in your code that may cause errors.

( 1 )
string.capitalize() will not change the value of the original string, therefore you have to assign it to a variable:

( 2 )
When performing comparisons with logical operators, and if you want to compare the same variable with different values, it should look like this:
if variable == "value1" or variable == "value2":

Additional:
You dont need to have "str" before input() as it already takes string by default.

https://code.sololearn.com/cdr5bf5TlSCA/?ref=app

Answer 2

The problem is happening after the : of your if statements and before print(num operation num1)

backspace from print until you delete the : then retype from there.

Did you use TAB?