Reject or loop over user input if two conditions n

问题:

I am a real beginner with Python, although I am loving every minute of it so far.

I am making a little program that takes user input and then does stuff with it. My issue is that the numbers the user inputs have to

(1) All add up to not more than one (i.e. a1+ a2+ a3 \leq 1)

(2) Each individually be < 1.

Here is my code thus far (just the essential middle bit):

 num_array = list()


  a1  = raw_input('Enter percentage a (in decimal form): ')
  a2 = raw_input('Enter percentage b (in decimal form): ')
  ...
  an = raw_input('Enter percentage n (in decimal form): ')


li = [a1, a2, ... , an]

for s in li:
   num_array.append(float(s))

And I would love to build in something to make it demand the user re-inputs things if their inputs either exceed the requirement that

a1+a2+a3 >1

or that a1>1, a2>1, a3>1 etc.

I have a feeling this would be really easy to implement, but with my limited knowledge I am stuck!

Any help would be much appreciated :-)

回答1:

input_list = []
input_number = 1
while True:

    input_list.append(raw_input('Enter percentage {} (in decimal form):'.format(input_number))

    if float(input_list[-1]) > 1:     # Last input is larger than one, remove last input and print reason
        input_list.remove(input_list[-1])
        print('The input is larger than one.')
        continue

    total = sum([float(s) for s in input_list])
    if total > 1:    # Total larger than one, remove last input and print reason
        input_list.remove(input_list[-1])
        print('The sum of the percentages is larger than one.')
        continue

    if total == 1:    # if the sum equals one: exit the loop
        break

    input_number += 1