Python NameError, variable 'not defined'

Question

the error it returns is:

NameError: name 'lives' is not defined

I know the code isn't as efficient as possible, this is one of my first projects, however whatever i try to do this error pops up, I've tried making a global for it but that didn't help. I would really appreciate some help with this, thanks!

import random
import time

def main():
 global guess,rand_num
 win = False
 rand_num = 45
 lives = 10
 while lives > 0 and win == False:
     guess = int(input("Guess a number!"))
     compare()
 print("Well done!")
 time.sleep(3)

def compare():
 global lives,win
 if guess == rand_num:
     print("You guessed correct!")
     win = True
 elif guess > rand_num:
     print ("Guess lower!")
     lives = lives - 1
 else:
     print ("Guess higher!")
     lives = lives - 1

def repeat():
 replay = input("would you like to play again? Y/N")
 if replay == "Y":
     print("enjoy!")
     main()
 elif replay == "N":
     "Goodbye then, hope you enjoyed!"
     time.sleep(3)
     os._exit
 else:
     print("please enter Y or N")
     repeat()

main()
repeat()

EDIT: putting global lives inside main() returns the error:

UnboundLocalError: local variable 'lives' referenced before assignment

Take a look at @chepner's answer. The global declaration should be in the main function. If you do that, your code works fine. — zondo
General recommendation: avoid global variables. Write functions, not procedures. Python programmers commonly use 4 spaces for indentation. — Eli Korvigo
i put the global for all 4, lives, win, rand_num and guess in both compare() and main() and that seemed to have worked, but i'm still unsure if all 4 are needed in both, or which ones are needed where. @Zondo — Kaos
why is avoiding global variables good @Eli Korvigo? (p.s it was the only way i could figure out how to do it, im new to coding as i said in my question ;P) — Kaos
You should declare the variable global if you are setting it in that function. To make x = 4 effect the global namespace, you need x to be declared global. To print x, you don't. — zondo

Carl 'Subzidion' Hiltbrunner Carl 'Subzidion' Hiltbrunner · Accepted Answer · 2016-06-21T22:02:49

You need to define the variable "lives" outside of the function main, then any function where you want to reference that global variable you say "global lives." When you are in a function and assign a value to a variable, it assumes it is in the local scope. using "global lives" tells that function to look to the global scope as the reference of lives.

import random
import time

lives = 10
win = False
guess = 0
rand_num = 45

def main():
    global guess, rand_num, lives, win
    win = False
    rand_num = 45
    lives = 10
    while lives > 0 and win == False:
        guess = int(input("Guess a number!"))
        compare()
    print("Well done!")
    time.sleep(3)

def compare():
    global guess, rand_num, lives, win
    if guess == rand_num:
        print("You guessed correct!")
        win = True
    elif guess > rand_num:
        print ("Guess lower!")
        lives = lives - 1
    else:
        print ("Guess higher!")
        lives = lives - 1

def repeat():
    replay = input("would you like to play again? Y/N")
    if replay == "Y":
        print("enjoy!")
        main()
    elif replay == "N":
        "Goodbye then, hope you enjoyed!"
        time.sleep(3)
        os._exit
    else:
        print("please enter Y or N")
        repeat()

main()
repeat()

Python NameError, variable 'not defined'

3 Answers