The position argument error and resolving it - python-3.x

Question

I am trying to implement a shopping cart in python and have this code but the error is that when i am calling a print_menu function , the arguments are not correct.
class ItemToPurchase:
def __init__(self, item_name= 'none', item_price=0, item_quantity=0, item_description = 'none'):
self.item_name = item_name
self.item_price = item_price
self.item_quantity = item_quantity
self.item_description = item_description
def print_item_cost(self):
string = '{} {} # ${} = ${}'.format(self.item_name, self.item_quantity, self.item_price, (self.item_quantity* self.item_price))
cost = self.item_quantity * self.item_price
return string, cost
def print_item_description(self):
string = '{}: {}'.format(self.item_name, self.item_description)
print(string, end=' ')
return string
class ShoppingCart:
def __init__(self,customer_name= None ,current_date='January 1,2016',cart_items=[]):
self.customer_name = customer_name
self.current_date = current_date
self.cart_items = cart_items
def add_item(self):
print('\nADD ITEM TO CART', end='\n')
item_name = str(input('Enter the item name:'))
item_description = str(input('\nEnter the item description:'))
item_price = int(input('\nEnter the item price:'))
item_quantity = int(input('\nEnter the item quantity:\n'))
self.cart_items.append(ItemToPurchase(item_name, item_price, item_quantity, item_description))
def remove_item(self):
print()
print('REMOVE ITEM FROM CART', end='\n')
string = str(input('Enter name of item to remove:\n'))
i = 0
for item in self.cart_items:
if(item.item_name == string):
del self.cart_items[i]
i += 1
flag=True
break
else:
flag=False
if(flag==False):
print('Item not found in cart. Nothing removed.')
def modify_item(self):
print('\nCHANGE ITEM QUANTITY', end='\n')
name = str(input('Enter the item name:'))
for item in self.cart_items:
if(item.item_name == name):
quantity = int(input('Enter the new quantity:'))
item.item_quantity = quantity
flag=True
break
else:
flag=False
if(flag==False):
print('Item not found in cart. Nothing modified.')
def get_num_items_in_cart(self):
num_items = 0
for item in self.cart_items:
num_items += item.item_quantity
return num_items
def get_cost_of_cart(self):
total_cost = 0
cost = 0
for item in self.cart_items:
cost = (item.item_quantity * item.item_price)
total_cost += cost
return total_cost
def print_total(self):
total_cost = self.get_cost_of_cart()
if (total_cost == 0):
print('SHOPPING CART IS EMPTY')
else:
self.output_cart()
def print_descriptions(self):
print('OUTPUT ITEMS\' DESCRIPTIONS')
print('{}\'s Shopping Cart - {}'.format(self.customer_name, self.current_date),end='\n')
print('\nItem Descriptions', end='\n')
for item in self.cart_items:
print('{}: {}'.format(item.item_name, item.item_description), end='\n')
def output_cart(self):
new=ShoppingCart()
print('OUTPUT SHOPPING CART', end='\n')
print('{}\'s Shopping Cart - {}'.format(self.customer_name, self.current_date),end='\n')
print('Number of Items:', new.get_num_items_in_cart(), end='\n\n')
self.total_cost = self.get_cost_of_cart()
if (self.total_cost == 0):
print('SHOPPING CART IS EMPTY')
else:
pass
tc = 0
for item in self.cart_items:
print('{} {} # ${} = ${}'.format(item.item_name, item.item_quantity,
item.item_price, (item.item_quantity * item.item_price)), end='\n')
tc += (item.item_quantity * item.item_price)
print('\nTotal: ${}'.format(tc), end='\n')
def print_menu(ShoppingCart):
customer_Cart = newCart
string=' '
#declare the string menu
menu = ('\nMENU\n'
'a - Add item to cart\n'
'r - Remove item from cart\n'
'c - Change item quantity\n'
'i - Output items\' descriptions\n'
'o - Output shopping cart\n'
'q - Quit\n')
command = ''
#Using while loop
#to iterate until user enters q
while(command != 'q'):
string=''
print(menu, end='\n')
#Prompt the Command
command = input('Choose an option: ')
#repeat the loop until user enters a,i,r,c,q commands
while (command != 'a' and command != 'o' and command != 'i' and command != 'r' and command != 'c' and command != 'q'):
command = input('Choose an option: ')
#If the input command is a
if(command == 'a'):
#call the method to the add elements to the cart
customer_Cart.add_item(string)
#If the input command is o
if(command == 'o'):
#call the method to the display the elements in the cart
customer_Cart.output_cart()
#If the input command is i
if(command == 'i'):
#call the method to the display the elements in the cart
customer_Cart.print_descriptions()
#If the input command is i
if(command == 'r'):
customer_Cart.remove_item()
if(command == 'c'):
customer_Cart.modify_item()
if __name__ == "__main__":
customer_name = str(input('Enter customer\'s name:'))
current_date = str(input('\nEnter today\'s date:'))
print()
print()
print('Customer name:', customer_name, end='\n')
print('Today\'s date:', current_date, end='\n')
newCart = ShoppingCart(customer_name, current_date)
newCart.print_menu(newCart)
i have created an instance of class ShopppingCart but it is not working. i am trying to get a user input and then display the menu for user to choose and implement one of the functions defined in the shopping cart class . Can anyone help me with resolving this issue.

Answer 1

This issue is happening because of function's argument, ShoppingCart. You have called the first argument ShoppingCart, which in reality is the ShoppingCart object; usually this is the self argument. Python does not care what you name it: self, ShoppingCart, corona. The first argument will always be the object that called the function. When calling this function with these lines of code:
newCart = ShoppingCart(customer_name, current_date)
newCart.print_menu(newCart)
you are using the newCart object to call the function and then passing the newCart object as an argument. You don't need to do this. Python already passes the object, so you don't have to.
I'm assuming this is the error you received:
Traceback (most recent call last):
File "c:/Users/jeffg/Desktop/ProgrammingProjects/StackOverFlow/shoppingcart.py", line 246, in <module>
newCart.print_menu(newCart)
TypeError: print_menu() takes 1 positional argument but 2 were given
This error takes place because you're function is defined to only take one argument. You didn't account for the self argument. To fix this, the code would need to be modified to something like this:
def print_menu(self, newCart):
customer_Cart = newCart
Although as discussed before, you don't need the newCart object to be passed, since you already have access to the newCart object with self. You can then slim down the function to this:
def print_menu(self):
And instead of using customer_Cart to call the functions, you can use self:
while (command != 'a' and command != 'o' and command != 'i' and command != 'r' and command != 'c' and command != 'q'):
command = input('Choose an option: ')
if(command == 'a'):
self.add_item(string)
I would also recommend using elif statements instead of using numerous if statements inside your print_menu() function.