Python while loop for validating input [duplicate]

Question

This question already has answers here:

Asking the user for input until they give a valid response (23 answers)

Closed 1 year ago.

I am very new to Python (started 3 days ago) and I am trying to make a loop where whenever the user inputs an invalid input, the code will respond and tell them to reenter their response but I cannot seem to get it.

while sub1!= "A,B,C,D,F":
 print("Invalid Entry,try again:")
 

• kuro: I suppose you want the user input to be any of A, B, C, D, F. Then change while loop to while sub1 not in ("A", "B", "C", "D", "F"):
• deadshot: what is invalid input in your case?
• Tasnuva Leeya: please add your invalid input

Answer 1

The user_inputs list and the for loop is to simulate different user inputs.

user_inputs = ['G','H','I','A','C']
for i in range(len(user_inputs)):
 # if user input is not in the list print valid (or do whatever you want to do)
 while user_inputs[i] not in ['A','B','C','D','F']:
 i+=1
 print('valid input')
 # if user input is in the list, then print invalid input... and break out of the loop
 else:
 print('invalid input')
 break

Answer 2

You can use if also to check condition

sub1 = "Z"
if not sub1 in ['A','B','C','D','F']:
..print("Invalid Entry,try again:")

• kuro: OP wants the user to retry in case of invalid input. So a loop will be better
• deadshot: OP wants an iterative solution not a if condition

Answer 3

using while loop and try-except:

while True:
 try:
 user_input = input()
 if user_input in "A, B, C, D, F".split(','):
 print("Valid Entry")
 break
 else:
 print("Invalid entry please try again")
 except ValueError:
 print("Provide A or B or C or D or F")
 continue