How to loop if response is not an option?

Question

So I've been working on this code and got stuck and was wondering if you guys could help me out.

# 31/05/17 (dd/mm/yy)
# encryption and decryption
#--------------------------------------------
print("Hello, in this program you will be able to encrypt your own message, 
and decrypt others")
#--------------------------------------------
ans = int(input("""
What would you like to do:
1. Encrypt your own message
2. Decrypt a message
Type the number corresponding to the action that you want to preform, then 
press ENTER
"""))
#--------------------------------------------
 if ans == 1:
  print("hi") 

#--------------------------------------------
 else ans == 2:
  code = input("""
:""")
#-------------------------------------------- 
break

#--------------------------------------------

How would I make it where if they don't enter a 1 or a 2, so it will just re-ask them?

Have you tried to write a while loop yet? – OneCricketeer Jun 02 '17 at 00:03 — OneCricketeer, Jun 02 '17 at 00:03
i dont know what while loop to use – Jordyn Wendling Jun 02 '17 at 00:04 — Jordyn Wendling, Jun 02 '17 at 00:04
It'd be useful to see what you tried, though – OneCricketeer Jun 02 '17 at 00:07 — OneCricketeer, Jun 02 '17 at 00:07

score 1 · Accepted Answer · answered Jun 02 '17 at 00:05

1

Create a while loop that will only break with a valid selection.

print("Please enter 1 or 2: ", end='')
while True:                        // always true
    choice = int(input()):
    if choice in (1, 2):
         break
    else:
        print("invalid entry, try again: ", end='')

if choice == 1:
    do somehting...
elif choice == 2:
    do something else...

answered Jun 02 '17 at 00:05

syntaxError

896
8
15

what does the end=' ' do? – Jordyn Wendling Jun 02 '17 at 00:10
The print statement usually defaults to end='\n', meaning at the end of a print statement it will start a new line by default in the terminal. By using end='' it means the print statement will not start a new line and instead ends with an empty string, so the input() statement be on the same line as the print statement, making it look nicer. – syntaxError Jun 02 '17 at 00:15
1

thanks for the help – Jordyn Wendling Jun 02 '17 at 00:17

John Mulder · Answer 2 · 2017-06-02T01:31:51.327

0

Here is a simple change that will get you most of the way there:

print("Hello, in this program you will be able to encrypt your own message, and decrypt others")
#--------------------------------------------
ans = int(input("""
What would you like to do:
1. Encrypt your own message
2. Decrypt a message
Type the number corresponding to the action that you want to preform, then 
press ENTER
"""))
#--------------------------------------------

while True:
  #--------------------------------------------
  if ans == 1:
    print("hi")
    break
  #--------------------------------------------
  elif ans == 2:
    code = input("""
    :""")
    break
  #--------------------------------------------
  else:
    ans = int(input("""
    What would you like to do:
    1. Encrypt your own message
    2. Decrypt a message
    Type the number corresponding to the
    action that you want to preform, then press ENTER"""))

edited Jun 02 '17 at 01:31

answered Jun 02 '17 at 00:08

John Mulder

9,765
7
33
37

Won't this have NameError? – OneCricketeer Jun 02 '17 at 00:14
yea, I skipped the first couple of lines, since they didn't change... I'll add them in. – John Mulder Jun 02 '17 at 01:30
Duplication of the `int(input(` part seems unncessary – OneCricketeer Jun 02 '17 at 01:43

score 0 · Answer 3 · answered Jun 02 '17 at 00:11

Try the bellow code

print("Hello, in this program you will be able to encrypt your own message,and decrypt others")
#--------------------------------------------
while True:
    try:ans = int(input("""
    What would you like to do:
    1. Encrypt your own message
    2. Decrypt a message
    Type the number corresponding to the action that you want to preform, then 
    press ENTER
    """))
    except:continue
    #--------------------------------------------
    if ans == 1:
      print("hi") 
      break
    #--------------------------------------------
    elif ans == 2:
      code = input("""
    :""")
      break

try except will help you re-ask when you enter non numbers too.

How to loop if response is not an option?

3 Answers3