Confusion with def-CodePudding

I'm making an attack system in python with def, but i got an error saying that the variable got referenced before assignment, eventhough i wrote it before the def. Does anyone know how?

import random
import time

monster = 20

def fight():
  print('Monster Spawned! Attack by 
typing A')
  A = str(input())

  while (A == 'A'):
    damage = range(1, 21)
    damage_done=(random.choice(damage))
    monster = monster - damage_done
    print('Slish Slash!')
    print(monster)
    print(damage_done)

fight()
if (monster < 0):
    print('Good Job')

EDIT 1: Error message is

Traceback (most recent call last):
File "main.py", line 17, in <module>
  fight()
File "main.py", line 12, in fight
  monster = monster - damage_done
UnboundLocalError: local variable 
'monster' referenced before assignment

CodePudding user response：

global monster
monster = monster - damage_done

you are in a function and it can't access a variable outside of it, so say to the function that there is a global variable with this name, outside and that it's a global variable... if not, it will be considered as a local variable and it will search for the monster variable inside the function

I think your code needs a rewrite:

import random
monster = 20
def fight():
  print('Monster Spawned! Attack by typing A')
  A = str(input())
  global monster
  if A == 'A':
      while monster > 0:
          damage = range(1, 21)
          damage_done=(random.choice(damage))
          monster = monster - damage_done
          print('Slish Slash!')
          print(monster)
          print(damage_done)
      else:
          print('Good Job')
fight()

you want a while to run unless monster < 0 and if monster < 0, then you want to print good job.

CodePudding user response：

Add global monster one line before monster=monster-damage_done If you don't add that then python recognizes monster as a local variable, thus the local variable is used before assignment.

CodePudding user response：

The variable monster is global, but the variable monster inside the fight() method is local, so, to specify that you want to assign the global variable, use global before monster.

def fight():
  print('Monster Spawned! Attack by typing A')
  A = str(input())

  global monster

  while (A == 'A'):
    damage = range(1, 21)
    damage_done=(random.choice(damage))
    monster = monster - damage_done
    print('Slish Slash!')
    print(monster)
    print(damage_done)

CodePudding user response：

the name of the variable declared in your init area and within the function only have one thing in common; a name. You can declare it as a global variable, or better yet pass the value to your defined function as an argument.

I would suggest renaming it something else within the function as that can be confusing.

import random
import time

monster = 20

def fight(monster):
  print('Monster Spawned! Attack by typing A')
  A = str(input())

  while (A == 'A'):
    damage = range(1, 21)
    damage_done=(random.choice(damage))
    monster = monster - damage_done
    print('Slish Slash!')
    print(monster)
    print(damage_done)

fight(monster)
if (monster < 0):
    print('Good Job')