Grocery app.py

# This loop will go on until the budget is integer or float
while True:
	try:
		bg = float(input("Enter your budget : "))
		# if budget is integer or float it will be stored
		# temporarily in variable 's'
		s = bg
	except ValueError:
		print("PRINT NUMBER AS A AMOUNT")
		continue
	else:
		break

# dictionary to store product("name"), quantity("quant"),
# price("price") with empty list as their values
a ={"name":[], "quant":[], "price":[]}

# converting dictionary to list for further updation
b = list(a.values())

# variable na value of "name" from dictionary 'a'
na = b[0]

# variable qu value of "quant" from dictionary 'a'
qu = b[1]

# variable pr value of "price" from dictionary 'a'
pr = b[2]

# This loop terminates when user select 2.EXIT option when asked
# in try it will ask user for an option as an integer (1 or 2)
# if correct then proceed else continue asking options
while True:
	try:
		ch = int(input("1.ADD\n2.EXIT\nEnter your choice : "))
	except ValueError:
		print("\nERROR: Choose only digits from the given option")
		continue
	else:
		# check the budget is greater than zero and option selected
		# by user is 1 i.e. to add an item
		if ch == 1 and s>0:	

			# input products name			
			pn = input("Enter product name : ")
			# input quantity of product
			q = input("Enter quantity : ")
			# input price of the product
			p = float(input("Enter price of the product : "))

			if p>s:
				# checks if price is less than budget
				print("\nCAN, T BUT THE PRODUCT")
				continue

			else:
				# checks if product name already in list
				if pn in na:
					# find the index of that product
					ind = na.index(pn)

					# remove quantity from "quant" index of the product
					qu.remove(qu[ind])

					# remove price from "price" index of the product
					pr.remove(pr[ind])

					# insert new value given by user earlier
					qu.insert(ind, q)

					# insert new value given by user earlier
					pr.insert(ind, p)

					# subtracting the price from the budget and assign
					# it to 's' sum(pr) is because pr = [100, 200] if
					# budget is 500 then s = bg-sum(pr) = 200
					# after updating for same product at index 0 let
					# pr = [200, 200] so s = 100
					s = bg-sum(pr)

					print("\namount left", s)
				else:
					# append value of in "name", "quantity", "price"
					na.append(pn)

					# as na = b[0] it will append all the value in the
					# list eg: "name":["rice"]
					qu.append(q)

					# same for quantity and price
					pr.append(p)

					# after appending new value the sum in price
					# as to be calculated
					s = bg-sum(pr)

					print("\namount left", s)

		# if budget goes zero print "NO BUDGET"
		elif s<= 0:
			print("\nNO BUDGET")
		else:
			break

# will print amount left in variable 's'
print("\nAmount left : Rs.", s)

# if the amount left equals to any amount in price list
if s in pr:
	# then printing the name of the product which can buy
	print("\nAmount left can buy you a", na[pr.index(s)])

print("\n\n\nGROCERY LIST")

# print final grocery list
for i in range(len(na)):
	print(na[i], qu[i], pr[i])