:TypeError: argument of type 'function' is not iterable", but works when individually tested

Question

I am a newbie to Python 2. I am trying to build a "shopping cart" Python program, but stuck at "check stock before put to cart" step.

Firstly, I have read many threads of the same problems in here, but they are seemingly of different cause from mine.

Secondly, I already separated each function and test in a different file. They worked well individually. But when joined back the check_stock(y) function, it gave the error.

I believe that the problem comes from the "in" command.

    def check_stock(y):             #// Problem in this function // 
        if y in list:
            print "%s is available" % y
            add_to_cart(y)
        else:
            print "Sorry, but %s is not available." % y

    def check_finish():
        y = raw_input(">")
        if y == "checkcart":        
            print cart              #check inside shopping cart
        elif y == " ":
            check_finish()          #loop back for blank
        elif y == "list":
            list()                  #present the list
        else:
            while y != "ok":        #"ok" = finished shopping
                check_stock(y)
            else:
                print "Checking out..."
                sorted(cart)
                print "Your item(s) are %s." % cart
                exit(0)

Here are the rest of the code, if it may help:

cart = []
list = ['apple', 'banana', 'cat', 'dog', 'elephant', 'flamingo', 'goofy', 'ham']
a = 0

def list():
    print list                  #present the list
def representInt(s):            #check if value is integer
    try:
        int(s)
        return True
    except ValueError:
        return False
def annoyedAtError(a):          #interaction for repeated mistakes
    if a < 2:
        print "Numbers only please"
    elif 2 < a < 4:
        print "Man, just do as I say, please. I have another shift tonight."
    elif a == 5 :
        print "Hey, seriously?"
    else:
        print "..."
def check_stock(y):             #// PROBLEM HERE // cross-check with list if item is available
    if y in list:
        print "%s is available" % y
        add_to_cart(y)
    else:
        print "Sorry, but %s is not available." % y

def add_to_cart(y):
    amount = (raw_input("How many do you want to add? > "))
    if representInt(amount) == False:
        annoyedAtError(a)
        global a 
        a = a + 1
        add_to_cart(y)
    else: 
        y = y + " " + amount
        print "%s is added to cart" % (y)
        cart.append(y)
        check_finish()
def check_finish():
    y = raw_input(">")
    if y == "checkcart":        
        print cart              #check inside shopping cart
    elif y == " ":
        check_finish()          #loop back for blank
    elif y == "list":
        list()                  #present the list
    else:
        while y != "ok":        #"ok" = finished shopping
            check_stock(y)
        else:
            print "Checking out..."
            sorted(cart)
            print "Your item(s) are %s." % cart
            exit(0)
def welcome():      
    print """\nWelcome to cyber shopping.\n 
    Please enter things you want to buy.
    Check your cart by typing: checkcart
    type "ok" when finished.
    type "list" for things available for buying"""
def start():
    welcome()
    check_finish()

start()

Answer 1

You created a list named list (which you shouldn't do, because it's a built in name already), but then you also create a function named list (again, don't do this). list refers to the function now, not your list. So when you check y in list it tries to check if the item is in the function. You can't use in on a function, hence the error. The solution is simple: use clearer names for things!!

Answer 2

lst = ['apple', 'banana', 'cat', 'dog', 'elephant', 'flamingo', 'goofy', 'ham']
a = 0

list is a predefined function in python, so use some other name.