LIST INDICES ERROR In Python 2.7, Please suggest solution for OPTION 1 in code

Question

Hi I have a doubt in calling a function with string name as it is showing error: LIST INDICES MUST BE AN INTEGER

I agree with the error statement but don't have the clue what to do. As when I am giving function argument parameter as a Dictionary , (option 2), its function is accepting it and running the code smoothly. But on giving it just the name of the key (as a I did in option 1), it is showing Indices error because I am accessing key which is a string not integer & it doesn't have the key with value (which is an error of unhashable key). So,

Please explain me following:

How to create a dictionary with key name but empty value. How to compare whether it is a list name is given in arguments of the function or a dictionary key. Please suggest code. Solution of my code. FOR OPTION 1

Code:

 # CODE FOR DETRMINING PRICE AS PER STOCK
#PYTHON 2.7 SCRIPT 
stock = {
    "banana": 6,
    "apple": 0,
    "orange": 32,
    "pear": 15
}

prices = {
    "banana": 4,
    "apple": 2,
    "orange": 1.5,
    "pear": 3
}

def compute_bill(food):
    x = 0
    total1 = 0
    total2 = 0
    z=0

    for key in food: # I KNOW I AM DOING ERROR HERE, BUT NO CLUE WHAT TO DO!!

        count = stock[key] #INTIAL COUNT
        print "this is the stock of %s : %d " % (key,count)

        count = stock[key] - food[key] # STOCK REMAINING
        print "this is the stock remaining of %s : %d " % (key,count)

        if count > 0: # CHECKING WHETHER IT IS IN STOCK OR NOT
            z = prices[key] * food[key] # FINDING TOTAL
            total1 = z + total1 # ACCUMLATING TOTAL
            print "this is the total1 of %s : %f \n" % (key,z)

        elif count <= 0: # OVER-STOCK OR EMPTY STOCK
            z = prices[key] * stock[key]
            total2 = z + total2
            print "this is the total2 of %s : %f \n" % (key,z)

        x = total1 + total2 #COMPUTING WHOLE TOTAL



    print "\n this is the whole total : %f \n" % x

    return x



 # JST WANT ALL PEAR
compute_bill(['pear']) #OPTION 1: NOT WORKING!! NEED SOLUTION

#OPTION 2 : WORKING : 
order = {'apple' : 1, 'banana' : 3, 'pear' : 3, 'orange' : 3}
    compute_bill(order)

Advance Thanks & Cheers!!

Answer 1

You need to check whether the passed in object is a dictionary (an order) or a list (an item) ... You also need to decide exactly what behavior you want in the second case, but let me guess you want to answer with the total price for the available stock:

def compute_bill(food):
    if isinstance(food, dict):
        compute_bill_for_order(food)
    if isinstance(food, list):
        compute_bill_for_items(food)

def compute_bill_for_order(order):
    for key in order.keys():  ## You also have to call the `keys` method
      # Here goes the exact same code you have for the cases
      # count > 0 and count <= 0
      # Basically, the `compute_bill` method
      pass

def compute_bill_for_items(items):
    total = 0
    for item in items:
        total += prices[item] * stock[item]
    return total