这个python程序怎么了？

Question

I am trying to make a Derp Simulator little game thing 'cuz I'm bored, and an issue popped up where if you try to buy catfood it adds catfood to the inventory but does not add it to the catfood count AND it doesn't take money away. I'm using a separate module for the shop than the actual game file so if anyone could try and find what's wrong I would appreciate it.

I called the shop function like this: shop(inv, balance, catfood, liqpota)

Shop Code:

from functions import *
def shop(inv, balance, catfood, liqpota):
while True:
    print "Welcome to the shop."
    print "-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-"
    print "( To purchase an item; enter the letter of the item. )"
    print "( If you want to exit; enter 'back'. )"
    print "A] $5 Cat Food - 'Not Just For Cats'"
    print "B] $7 Liquified Potatoes - 'Who Would Want These?'"
    print
    com = raw_input("Purchase: ")
    divider()
    if com == "back" or com == "Back":
        break
    elif com == "a" or com == "A":
        if "Cat Food" in inv:
            if balance < 7:
                print "You have insufficient funds."
            elif balance > 7 or balance == 7:
                catfood = catfood + 1
                balance = balance - 7
                print "Purcahse succcessful."
                return catfood
                return liqpota
        if not "Cat Food" in inv:
            if balance < 7:
                print "You have insufficient funds."
            elif balance > 7 or balance == 7:
                catfood = catfood + 1
                balance = balance - 7
                inv.append("Cat Food")
                print "Purchase successful."
                return catfood
                return liqpota
    elif com == "b" or com == "B":
        print "WIP"
        break
    else:
        print "Invalid Item/Command."
    divider()

Main Code: (Inventory Part)

elif com == "inventory" or com == "Inventory":
    tmp_invnum = 1
    print "Cat Food = " + str(catfood)
    print "Liquified Potatoes = " + str(liqpota)
    print
    for invf in inv:
        print str(tmp_invnum) + "] " + invf
        tmp_invnum += 1

Answer 1

The second return statement (return liqpota) is never executed because your function ends at the first return encountered. You can return all the values in a single statement and unpack them at the function call. I've included an example below.

def divider():
    print '*' * 80

def shop(inv, balance, catfood, liqpota):
    while True:
        print "Welcome to the shop."
        print "-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-"
        print "( To purchase an item; enter the letter of the item. )"
        print "( If you want to exit; enter 'back'. )"
        print "A] $5 Cat Food - 'Not Just For Cats'"
        print "B] $7 Liquified Potatoes - 'Who Would Want These?'"
        print
        com = raw_input("Purchase: ")
        divider()
        if com == "back" or com == "Back":
            break
        elif com == "a" or com == "A":
            if "Cat Food" in inv:
                if balance < 7:
                    print "You have insufficient funds."
                elif balance > 7 or balance == 7:
                    catfood = catfood + 1
                    balance = balance - 7
                    print "Purcahse succcessful."
                    # return all four variables at once
                    return (catfood,liqpota,inv,balance)

            if not "Cat Food" in inv:
                if balance < 7:
                    print "You have insufficient funds."
                elif balance > 7 or balance == 7:
                    catfood = catfood + 1
                    balance = balance - 7
                    inv.append("Cat Food")
                    print "Purchase successful."
                    # return all four variables at once
                    return (catfood,liqpota,inv,balance)

        elif com == "b" or com == "B":
            print "WIP"
            break
        else:
            print "Invalid Item/Command."

        divider()

    return (catfood,liqpota,inv,balance)

catfood = 0
liquified_potatoes = 0
balance = 30
inv = []

print 'catfood %s potatoes %s inventory %s balance %s' % (catfood,liquified_potatoes,inv,balance)

catfood, liquified_potatoes, inv, balance = shop(inv, balance, catfood, liquified_potatoes)        

print 'catfood %s potatoes %s inventory %s balance %s' % (catfood,liquified_potatoes,inv,balance)