Editing an Integer from one def to another

Question

Hello and apologies if a similar question has been answered, but I cannot find similar post. I am still rather new with python 3 and English is a little rough.

I start the program and it goes to character_start() where it ask for a name and sets a health variable to 10. It then calls the main() where it says the health again and it ask the user where they want to go. As for now the only option is 1 and that takes you to the trap() function. The user will be hit by 1 health and it should go back to main() where it will show them with 1 missing health.

I think the problem is it does not recognize the user_health as a global variable even when I write it outside of a def.

Thank you and here is my code.

import random

def character_start():
    user_name = input("Name: ")
    user_health = 10
    main()


def main():
    print("Health: ", user_health)
    print("Type 1 to walk into a trap.")
    main_choice = int(input("Choice: "))
    if (main_choice == 1): trap()


def trap():
    user_health = user_health - 1
    print("1 point of damage.")
    main()


character_start()

The following code doesn't run since `user_health` is undefined. Could you provide a version that runs and then explain what you would like to change. — a_guest, Apr 29 '20 at 12:16

Jake Tae · Accepted Answer · 2020-04-29T12:27:11.233

Welcome to SO. This is a great community to learn and grow, so hope you can make the best out of it.

As you've pointed out yourself, main and trap have no knowledge of user_health, since the scope of user_health is confined to the limits of character_start. While the use of global variables is usually not recommended for a variety of reasons I won't elaborate here (for that, you can refer to this thread), but presented below is one possible implementation. Modified code segments have accompanying comments for reference.

import random

user_health = 10 # declare global var


def character_start():
    user_name = input("Name: ")
    main()


def main():
    print("Health: ", user_health) # main has access to user_health
    print("Type 1 to walk into a trap.")
    main_choice = int(input("Choice: "))
    if (main_choice == 1):
        trap()


def trap():
    global user_health # tell trap that user_health is a global var
    user_health = user_health - 1 # alter that global var
    print("1 point of damage.")
    main()


character_start()

The key takeaway here is that

Global variables are declared outside the scope of any function
If you want to modify a global variable, tell the function explicitly that a certain variable name refers to a global variable via the global keyword (as shown in the trap function)

ohhhhhhhhh I see now. Thankyou for that. Why does main have access but trap does not initially? — Dan the man 007, Apr 29 '20 at 12:27
Glad it helped! The short answer is that in `main`, we only access the variable, whereas in `trap`, we assign a value to the variable. For assignment, a `global` keyword specification is necessary. See examples [here](https://www.geeksforgeeks.org/global-keyword-in-python/). — Jake Tae, Apr 29 '20 at 12:31
Now I am seeing the bigger picture these examples are perfect. Thank you again! I will read all these links you sent me. — Dan the man 007, Apr 29 '20 at 12:32

Editing an Integer from one def to another

1 Answers1