Checking string for correct input

Question

Im doing an activity to extend my existing code to check for user input and I can't get it to work properly.

First attempt:

while 5 > appcounter:
    StudentGender.append (input(StudentName[namecount]+",Please Enter Student Gender M or F:"))
    if StudentGender[appcounter] == "M":
        appcounter = appcounter + 1
        namecount = namecount + 1
    elif StudentGender[appcounter] == "F":
        appcounter = appcounter + 1
        namecount = namecount + 1
    else:
        print("Not a valid input")

Second Try

for Counter in range (ConstNoStudents+1):
    try:
        StudentGender[Counter] = (input(StudentName[namecount]+",are you Male or Female, Please use M or F:") )
        StudentGender[Counter] = "M" or "F" or "f" or "m"
        namecount = listcount+1
    except:
        print("That is not a valid number")

I ideally want it to identify when the user type's something other than M or F in and Get the user to re-enter the value without adding anything extra to the list

You'd better validate the input before appending it to StudentGender. — Stop harming Monica
– Stop harming Monica, Commented Apr 12, 2019 at 12:36

Pierre Gourseaud · Accepted Answer · 2019-04-12 12:33:06Z

1

Rearranging your code, you need to prompt the user again if his input is invalid. You can do so with a while loop :

for index in range(ConstNoStudents+1):
    input = input(StudentName[index]+", are you Male or Female, Please use M or F:")
    while not input.upper() in ["M", "F"]:
        input = input("Invalid input. Please use M or F :")
    StudentGender[index] = input

answered Apr 12, 2019 at 12:33

Pierre Gourseaud

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Comments

Louis Saglio · Accepted Answer · 2019-04-12 12:30:24Z

1

Use this pattern:

accepted_inputs = ["M", "F"]
while True:
    user_input = input("message")
    if user_input in accepted_inputs:
        break
    print("Bad input, try again")

answered Apr 12, 2019 at 12:30

Louis Saglio

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DobromirM · Accepted Answer · 2019-04-12 12:36:08Z

1

You would need to get the input in a loop and check if one of the correct values was entered and if it was not, then repeat the loop.

You can also apply .upper() to the gender selection, instead of specifying the lower case versions of the gender values.

invalid_gender = True
while invalid_gender:
    gender = input('Please Enter Student Gender (M or F):')

    if gender.upper() not in ['M', 'F']:
        print('Invalid gender! Please, try again.')
    else:
        invalid_gender = False

edited Apr 12, 2019 at 12:36

answered Apr 12, 2019 at 12:29

DobromirM

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