while/for 循环中的错误是什么？

Question

This is the output using the wrong for/while-loop operation:

current value is 60

current value is 120

total value is 120

This is what I would like it to be:

current value is 10

current value is 30

total value is 30

prices = [10, 20, 30]
total = 0
steps = 0
step_limit = 2
while steps < step_limit:
    steps +=1
    for i in prices:
        total += i
    print(f'current value is {total}')
print(f'total value is {total}')

Answer 1

If you want to add each element from the list, the problem that arises here is in the following part of your code:

for i in prices:
    total += i

This means that you iterate through each element inside the list and add it to the total (10+20+30). This is done 2 times, so the total will be 120.

You have to replace that part of the code with something that accesses only one element at a time. For instance:

total += prices[steps]

If you desire to add the last element and display the total straight away with it, you can add the last price outside of the while loop right before the message display at the end:

total += prices[steps]
print(f'total value is {total}')