需要哪个循环以及如何合并它

Question

import time

Time_started=time.ctime()
Question1=input("Has vehicle gone past sensor 1 \n:")
if Question1=="yes":
    Confirmation1=input("Confirm? \n:")
elif Question1 !="yes":
    Question1=input("Has vehicle gone past sensor 1 \n:")
if Confirmation1=="yes":
    print ("Vehicle entered on",Time_started)
elif Confirmation1!="yes":
    Question1=input("Has vehicle gone past sensor 1 \n:")

Time_ended=time.ctime()
Question2=input("Has vehicle gone past sensor 2 \n:")
if Question2=="yes":
    Confirmation2=input("confirm? \n:")
elif Question2 !="yes":
    Question2=input("Has vehicle gone past sensor 2 \n:")
if Confirmation2=="yes":
    print("Vehicle left on",Time_ended) 
elif Confirmation !="yes":
    Question2=input("Has vehicle gone past sensor 2 \n:")

Here's what happened:

Has vehicle gone past sensor 1 
:yes
Confirm? 
:no
Has vehicle gone past sensor 1 
:yes
Has vehicle gone past sensor 2 
:yes
confirm? 
:

What should have happened:

The second time the program asked "has vehicle gone past sensor 1" and the user input was "yes" the program should have asked "confirm?" but this didn't happen instead it went straight to the second question.

I know that a loop is needed, however I do not know which loop and how to incorporate it.

Answer 1

Just loop until the first confirmation is answered affirmatively:

answer_to_confirmation_1 = None  # As long as we haven't asked,
                                 # there can't be an answer. ;-)
while answer_to_confirmation_1 != 'yes':
    answer_to_question_1 = input("Has vehicle gone past sensor 1 \n:")
    if answer_to_question_1 == 'yes':
        answer_to_confirmation_1 = input("Confirm? \n:")

# If we ever exit above loop, we can be sure of the following:
print('The user has confirmed that the vehicle has passed sensor 1.')

Answer 2

For putting input confirmation within a loop, you can see das-g's answer for your specific circumstance. However, it looks like your code isn't quite doing what you want. If you're trying to set the time after the person enters their input, then you will need to call time.ctime() after input() returns.

Also, it looks like you're duplicating code by doing the same procedure twice. I'd recommend creating a function instead that you can call multiple times, such as this:

def confirm_time(prompt):
    while True:
        if input(prompt) == "yes":
            input_time = time.ctime()
            if input("Confirm time '{}'\n:".format(input_time)) == "yes":
                return input_time

Then you can call that function twice with the different prompts that you want, like this:

time_started = confirm_time("Enter yes when the vehicle passes sensor 1 \n:")
print("Vehicle entered on", time_started)
time_ended = confirm_time("Enter yes when the vehicle passes sensor 2 \n:")
print("Vehicle left on", time_ended)

Using that, I get the following output:

Enter yes when the vehicle passes sensor 1
:yes
Confirm time 'Sat Nov  7 19:04:33 2015'
:no
Enter yes when the vehicle passes sensor 1
:yes
Confirm time 'Sat Nov  7 19:04:41 2015'
:yes
Vehicle entered on Sat Nov  7 19:04:41 2015
Enter yes when the vehicle passes sensor 2
:yes
Confirm time 'Sat Nov  7 19:04:47 2015'
: