If I copy and paste your code as you show it, it works fine.
But .... if I add one line, then it fails the same way you get:
password = ''
input = ''
while password != 'password':
print("What is the password?")
password = input()
print('Yes, the password is ' + password + '. You may enter.')
It fails because I have declared a variable called
input
and that "overwrites" the definition of the standard function called
input
- so the system assumes you are trying to call a string as a function and complains.
Check your code above that, and see if you have a variable called
input
- and change it if you do!