validate user input by length in Python

Question

I have some code:

def GetPlayerName():
  print()
  PlayerName = input('Please enter your name: ')
  print()
  return PlayerName

How can I keep asking for the player's name until they enter a name that is more than one character long, and tell them they must enter a valid name if they leave the field blank?

I tried

def GetPlayerName():
  print()
  PlayerName = input('Please enter your name: ')
  print()
  return PlayerName
  while len(PlayerName) < 1:
    print("You must enter a name!")

but have been unsuccessful.

Well, it could be helpful if you'd show us your solution so we can say why it doesn't work. — TidB
– TidB, Commented Jan 19, 2015 at 20:07
Regarding the last edit: How would you expect the value of PlayerName to change in the loop? — TidB
– TidB, Commented Jan 19, 2015 at 20:11
@Iplodman Read the section titled: "Implementing Your Own Validation Rules". Swap the requirement that the input is in all caps for the requirement that the length is greater than one, and you have this question. — jme
– jme, Commented Jan 19, 2015 at 20:24

Anshul Goyal · Accepted Answer · 2015-01-19 20:23:44Z

3

Use a while loop to get the input repetitively:

def get_player_name():
    print()
    player_name = ""
    while len(player_name) <= 1: 
        player_name = input('Please enter your name: ')
        print()
    return player_name

The way you are currently using it, you use the while statement to only print the error message.

PS: I've converted your variable names etc to small_caps_format because that is what PEP recommends.

edited Jan 19, 2015 at 20:23

answered Jan 19, 2015 at 20:09

Anshul Goyal

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2 Comments

jme Over a year ago

The question wanted to ensure len(player_name) > 1, so you'll need <= rather than < in the while's predicate. Also, it would be nice to print an error message if the user inputs a bad name. It can be more succinct to do that if you use the while True idiom.

Anshul Goyal Over a year ago

@jme thanks for the suggestions, made changes regarding the len > 1, As for the other, there is already another answer for the while True idiom..

HarryCBurn · Accepted Answer · 2015-01-19 20:28:55Z

2

def GetPlayerName():
    print()

    while True:
        PlayerName = input('Please enter your name: ')

        if len(PlayerName) > 1:
            break
        print("Your name is too short! :c")

    print()
    return PlayerName

One solution amongst others, and doesn't require any variables outside of the while loop. As mentioned by @jme, the error message is rather easy to print with this solution. The issue with your code is that:

Your while loop is after the return statement is called, so it's affectively rendered mute.
Your while loop is infinite-- it doesn't give the user a chance to re-try!

edited Jan 19, 2015 at 20:28

answered Jan 19, 2015 at 20:12

HarryCBurn

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2 Comments

jme Over a year ago

A single line can be added to this solution to print an error message on invalid input. The other solutions require a bit more work. That might be an advantage worth mentioning in your answer.

An0n Over a year ago

Whats the point of the while True if you don't have a continue in it ? That way you get big problems when working on bigger programs. But i like your style tho..

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