Thank you mtf & Conditional Statement Question


#1

Here is my new code. Thank you mtf. Also, I have a question about if, else, and elif statements. If you have a if statement, is it mandatory to have a corresponding else and elif statement. Or is it okay to have one without the other. In my code I only put a if statement. Could you please explain what happens if stock[item] <= 0 since I don't have a else statement in my code (specifically).

shopping_list = ["banana", "orange", "apple"]

stock = {
"banana": 6,
"apple": 0,
"orange": 32,
"pear": 15
}

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

def compute_bill(shopping_list):
total = 0
for item in shopping_list:
if stock[item] > 0:
total += prices[item]
stock[item] -= 1
return total


#2

When there is only a 'yes' / 'no' scenario, with only one action to perform,

if condition:
    # action for True

Where there is an alternate action,

if condition:
    # action for True
else:
    # default action

When we are not bypassing any code, we can write,

if condition:
    # code
if state:
    # code
if something:
    # code

In the above, each statement is independent, and all three are evaluated (no interruption in flow).

When there are multiple cases from which only one case can be true, we introduce, elif...

if condtion1:
    # condition1 action
elif condition2:
    # condition2 action
elif condtion3:
    # condition3 action

Flow will only pass through one of the branches given a True condition. Unless there is a default action within the control flow, else is not required.

In any if statement, there is no limit on the number of elif cases, but there can only ever be one else, or default clause. else never appears before elif.