Is there a better way to evaluate user inputs without a 'for' loop and changing a checker from False to True?

Very new to python and have been, as an exercise, doing a text-based version of a board game (I'm an avid board gamer).

There are obviously lots of places for the user to input something, and naturally I need to evaluate those inputs and make sure they are valid.

I learned about using a True/False check and for loops from this site (thanks!) and now that I've done them so much I was wondering if there was a better way - they get a little crazy if they are nested and I want to to my best to adhere to those Zen-like Python rules.

Here is what I mean, in a simple example, using generic code so it makes sense (not all of you may know the rules of this board game!)

The goal is to make sure the code loops until a color or "none" is given. I know this accomplishes that, i'm just wondering if there is a more streamlined way that I haven't learned yet.

colors = ["red", "green", "white", "blue", "yellow"]



for color in colors:

    print(f"You can choose {color}.")



choice = input("Which color would you choose? (input a color or 'none' : ")

checker = False



while not checker:

    if choice not in colors:

        choice = input("That's not one of your options. Choose again: ")



    elif choice == "none":

        print("You don't want a color. That's fine.")

        checker = True



    else:

        print("You chose {color}! Have fun!")

        checker = True

edited Nov 20 '18 at 0:39

cricket_007

80k1142110

asked Nov 20 '18 at 0:37

Jonathan

314

3

this looks reasonable ...

– Joran Beasley
Nov 20 '18 at 0:40

Think about a full-blown argument parser like argparse or click - they don't need to be used on the program's command-line argument. Even if you don't actually use one of them, the mindset may be useful.

– o11c
Nov 20 '18 at 0:48

add a comment |

Very new to python and have been, as an exercise, doing a text-based version of a board game (I'm an avid board gamer).

There are obviously lots of places for the user to input something, and naturally I need to evaluate those inputs and make sure they are valid.

Here is what I mean, in a simple example, using generic code so it makes sense (not all of you may know the rules of this board game!)

The goal is to make sure the code loops until a color or "none" is given. I know this accomplishes that, i'm just wondering if there is a more streamlined way that I haven't learned yet.

colors = ["red", "green", "white", "blue", "yellow"]



for color in colors:

    print(f"You can choose {color}.")



choice = input("Which color would you choose? (input a color or 'none' : ")

checker = False



while not checker:

    if choice not in colors:

        choice = input("That's not one of your options. Choose again: ")



    elif choice == "none":

        print("You don't want a color. That's fine.")

        checker = True



    else:

        print("You chose {color}! Have fun!")

        checker = True

edited Nov 20 '18 at 0:39

cricket_007

80k1142110

asked Nov 20 '18 at 0:37

Jonathan

314

3

this looks reasonable ...

– Joran Beasley
Nov 20 '18 at 0:40

Think about a full-blown argument parser like argparse or click - they don't need to be used on the program's command-line argument. Even if you don't actually use one of them, the mindset may be useful.

– o11c
Nov 20 '18 at 0:48

add a comment |

Very new to python and have been, as an exercise, doing a text-based version of a board game (I'm an avid board gamer).

There are obviously lots of places for the user to input something, and naturally I need to evaluate those inputs and make sure they are valid.

Here is what I mean, in a simple example, using generic code so it makes sense (not all of you may know the rules of this board game!)

The goal is to make sure the code loops until a color or "none" is given. I know this accomplishes that, i'm just wondering if there is a more streamlined way that I haven't learned yet.

colors = ["red", "green", "white", "blue", "yellow"]



for color in colors:

    print(f"You can choose {color}.")



choice = input("Which color would you choose? (input a color or 'none' : ")

checker = False



while not checker:

    if choice not in colors:

        choice = input("That's not one of your options. Choose again: ")



    elif choice == "none":

        print("You don't want a color. That's fine.")

        checker = True



    else:

        print("You chose {color}! Have fun!")

        checker = True

edited Nov 20 '18 at 0:39

cricket_007

80k1142110

asked Nov 20 '18 at 0:37

Jonathan

314

Very new to python and have been, as an exercise, doing a text-based version of a board game (I'm an avid board gamer).

There are obviously lots of places for the user to input something, and naturally I need to evaluate those inputs and make sure they are valid.

Here is what I mean, in a simple example, using generic code so it makes sense (not all of you may know the rules of this board game!)

The goal is to make sure the code loops until a color or "none" is given. I know this accomplishes that, i'm just wondering if there is a more streamlined way that I haven't learned yet.

colors = ["red", "green", "white", "blue", "yellow"]



for color in colors:

    print(f"You can choose {color}.")



choice = input("Which color would you choose? (input a color or 'none' : ")

checker = False



while not checker:

    if choice not in colors:

        choice = input("That's not one of your options. Choose again: ")



    elif choice == "none":

        print("You don't want a color. That's fine.")

        checker = True



    else:

        print("You chose {color}! Have fun!")

        checker = True

python python-3.x

edited Nov 20 '18 at 0:39

cricket_007

80k1142110

asked Nov 20 '18 at 0:37

Jonathan

314

edited Nov 20 '18 at 0:39

cricket_007

80k1142110

asked Nov 20 '18 at 0:37

Jonathan

314

edited Nov 20 '18 at 0:39

cricket_007

80k1142110

edited Nov 20 '18 at 0:39

cricket_007

80k1142110

edited Nov 20 '18 at 0:39

cricket_007

80k1142110

asked Nov 20 '18 at 0:37

Jonathan

314

asked Nov 20 '18 at 0:37

Jonathan

314

asked Nov 20 '18 at 0:37

Jonathan

314

3

this looks reasonable ...

– Joran Beasley
Nov 20 '18 at 0:40

Think about a full-blown argument parser like argparse or click - they don't need to be used on the program's command-line argument. Even if you don't actually use one of them, the mindset may be useful.

– o11c
Nov 20 '18 at 0:48

add a comment |

3

this looks reasonable ...

– Joran Beasley
Nov 20 '18 at 0:40

Think about a full-blown argument parser like argparse or click - they don't need to be used on the program's command-line argument. Even if you don't actually use one of them, the mindset may be useful.

– o11c
Nov 20 '18 at 0:48

this looks reasonable ...

– Joran Beasley
Nov 20 '18 at 0:40

Think about a full-blown argument parser like argparse or click - they don't need to be used on the program's command-line argument. Even if you don't actually use one of them, the mindset may be useful.

– o11c
Nov 20 '18 at 0:48

add a comment |

3 Answers
3

active

oldest

votes

You could define a generic function if you find yourself repeating the same things

def prompt_for_valid_input(options):

    while True:

        print(f"You can choose one of {options}.")

        choice = input("Which would you choose? (or 'none' : ")

        if choice == "none" and "none" not in options:

            print("You didn't pick anything. That's fine.")

            return None

        elif choice in options:

            return choice

        else:

            print("That's not one of your options. Choose again. ")



colors = ["red", "green", "white", "blue", "yellow"]

color = prompt_for_valid_input(colors)

if color is not None:

    print(f"You chose {color}! Have fun!")



numbers = [1, 10, 100]

num = prompt_for_valid_input(numbers)

if num is not None:

    print(f"You chose {num}! Have fun!")

So "without a while/for loop", not really. Without a sentinel variable, yes, if the conditions are simple enough.

answered Nov 20 '18 at 0:45

cricket_007

80k1142110

Thanks for this, I like this idea. In my code, often times entering a certain input launches a function which itself might have more input validators. I like this idea and can probably implement it wisely in the right spots.

– Jonathan
Nov 20 '18 at 0:54

add a comment |

you can abstract it out to a generic validated input method

def validated_input(prompt,validation_method,error_message):

    while True:

         result = input(prompt)

         if validation_method(result):

            return result

         print(error_message)





choices = ['red','green','blue','none']

validator = lambda test:test.lower().strip() in choices

prompt = "Enter A Color(one of Red, Green, Blue, or None):"

error_message = "Please enter a valid color or None!"



print(validated_input(prompt,validator,error_message))

its arguable whether this is "better"

answered Nov 20 '18 at 0:45

Joran Beasley

72.5k678118

Thanks Jordan. I see now how a function like this can actually help me a lot. Often my validations lead to a function, and sometimes those have more validations. I'll play with these kind of constructions and see if i can improve the code!

– Jonathan
Nov 20 '18 at 0:56

*Joran! want to get your name right.

– Jonathan
Nov 20 '18 at 1:12

add a comment |

Usually how you wrote your code is considered pretty "normal" and straightforward which is good. The issue is that you would want the looping part of your code to repeat till it has met its expectation. So a conditional looping event is necessary. If you really want you can simplify it a little by making a break statement for example:

x = 0

while True:

  if x == 12:

     break;

  else:

     x = x + 1

print(x)

This will create a infinite loop until the condition you are looking for is met and then it will break out of the loop. Make sure you have your escape condition though.

answered Nov 20 '18 at 1:24

Jay Patel

261

add a comment |

Your Answer

StackExchange.ifUsing("editor", function () {
StackExchange.using("externalEditor", function () {
StackExchange.using("snippets", function () {
StackExchange.snippets.init();
});
});
}, "code-snippets");

StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "1"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});

function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});

}
});

draft saved

draft discarded

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Post as a guest

Name

Required, but never shown

StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53384614%2fis-there-a-better-way-to-evaluate-user-inputs-without-a-for-loop-and-changing%23new-answer', 'question_page');
}
);

Post as a guest

Name

Required, but never shown

3 Answers
3

active

oldest

votes

3 Answers
3

active

oldest

votes

You could define a generic function if you find yourself repeating the same things

def prompt_for_valid_input(options):

    while True:

        print(f"You can choose one of {options}.")

        choice = input("Which would you choose? (or 'none' : ")

        if choice == "none" and "none" not in options:

            print("You didn't pick anything. That's fine.")

            return None

        elif choice in options:

            return choice

        else:

            print("That's not one of your options. Choose again. ")



colors = ["red", "green", "white", "blue", "yellow"]

color = prompt_for_valid_input(colors)

if color is not None:

    print(f"You chose {color}! Have fun!")



numbers = [1, 10, 100]

num = prompt_for_valid_input(numbers)

if num is not None:

    print(f"You chose {num}! Have fun!")

So "without a while/for loop", not really. Without a sentinel variable, yes, if the conditions are simple enough.

answered Nov 20 '18 at 0:45

cricket_007

80k1142110

Thanks for this, I like this idea. In my code, often times entering a certain input launches a function which itself might have more input validators. I like this idea and can probably implement it wisely in the right spots.

– Jonathan
Nov 20 '18 at 0:54

add a comment |

You could define a generic function if you find yourself repeating the same things

def prompt_for_valid_input(options):

    while True:

        print(f"You can choose one of {options}.")

        choice = input("Which would you choose? (or 'none' : ")

        if choice == "none" and "none" not in options:

            print("You didn't pick anything. That's fine.")

            return None

        elif choice in options:

            return choice

        else:

            print("That's not one of your options. Choose again. ")



colors = ["red", "green", "white", "blue", "yellow"]

color = prompt_for_valid_input(colors)

if color is not None:

    print(f"You chose {color}! Have fun!")



numbers = [1, 10, 100]

num = prompt_for_valid_input(numbers)

if num is not None:

    print(f"You chose {num}! Have fun!")

So "without a while/for loop", not really. Without a sentinel variable, yes, if the conditions are simple enough.

answered Nov 20 '18 at 0:45

cricket_007

80k1142110

Thanks for this, I like this idea. In my code, often times entering a certain input launches a function which itself might have more input validators. I like this idea and can probably implement it wisely in the right spots.

– Jonathan
Nov 20 '18 at 0:54

add a comment |

You could define a generic function if you find yourself repeating the same things

def prompt_for_valid_input(options):

    while True:

        print(f"You can choose one of {options}.")

        choice = input("Which would you choose? (or 'none' : ")

        if choice == "none" and "none" not in options:

            print("You didn't pick anything. That's fine.")

            return None

        elif choice in options:

            return choice

        else:

            print("That's not one of your options. Choose again. ")



colors = ["red", "green", "white", "blue", "yellow"]

color = prompt_for_valid_input(colors)

if color is not None:

    print(f"You chose {color}! Have fun!")



numbers = [1, 10, 100]

num = prompt_for_valid_input(numbers)

if num is not None:

    print(f"You chose {num}! Have fun!")

So "without a while/for loop", not really. Without a sentinel variable, yes, if the conditions are simple enough.

answered Nov 20 '18 at 0:45

cricket_007

80k1142110

You could define a generic function if you find yourself repeating the same things

def prompt_for_valid_input(options):

    while True:

        print(f"You can choose one of {options}.")

        choice = input("Which would you choose? (or 'none' : ")

        if choice == "none" and "none" not in options:

            print("You didn't pick anything. That's fine.")

            return None

        elif choice in options:

            return choice

        else:

            print("That's not one of your options. Choose again. ")



colors = ["red", "green", "white", "blue", "yellow"]

color = prompt_for_valid_input(colors)

if color is not None:

    print(f"You chose {color}! Have fun!")



numbers = [1, 10, 100]

num = prompt_for_valid_input(numbers)

if num is not None:

    print(f"You chose {num}! Have fun!")

So "without a while/for loop", not really. Without a sentinel variable, yes, if the conditions are simple enough.

answered Nov 20 '18 at 0:45

cricket_007

80k1142110

answered Nov 20 '18 at 0:45

cricket_007

80k1142110

answered Nov 20 '18 at 0:45

cricket_007

80k1142110

answered Nov 20 '18 at 0:45

cricket_007

80k1142110

Thanks for this, I like this idea. In my code, often times entering a certain input launches a function which itself might have more input validators. I like this idea and can probably implement it wisely in the right spots.

– Jonathan
Nov 20 '18 at 0:54

add a comment |

Thanks for this, I like this idea. In my code, often times entering a certain input launches a function which itself might have more input validators. I like this idea and can probably implement it wisely in the right spots.

– Jonathan
Nov 20 '18 at 0:54

Thanks for this, I like this idea. In my code, often times entering a certain input launches a function which itself might have more input validators. I like this idea and can probably implement it wisely in the right spots.

– Jonathan
Nov 20 '18 at 0:54

add a comment |

you can abstract it out to a generic validated input method

def validated_input(prompt,validation_method,error_message):

    while True:

         result = input(prompt)

         if validation_method(result):

            return result

         print(error_message)





choices = ['red','green','blue','none']

validator = lambda test:test.lower().strip() in choices

prompt = "Enter A Color(one of Red, Green, Blue, or None):"

error_message = "Please enter a valid color or None!"



print(validated_input(prompt,validator,error_message))

its arguable whether this is "better"

answered Nov 20 '18 at 0:45

Joran Beasley

72.5k678118

Thanks Jordan. I see now how a function like this can actually help me a lot. Often my validations lead to a function, and sometimes those have more validations. I'll play with these kind of constructions and see if i can improve the code!

– Jonathan
Nov 20 '18 at 0:56

*Joran! want to get your name right.

– Jonathan
Nov 20 '18 at 1:12

add a comment |

you can abstract it out to a generic validated input method

def validated_input(prompt,validation_method,error_message):

    while True:

         result = input(prompt)

         if validation_method(result):

            return result

         print(error_message)





choices = ['red','green','blue','none']

validator = lambda test:test.lower().strip() in choices

prompt = "Enter A Color(one of Red, Green, Blue, or None):"

error_message = "Please enter a valid color or None!"



print(validated_input(prompt,validator,error_message))

its arguable whether this is "better"

answered Nov 20 '18 at 0:45

Joran Beasley

72.5k678118

Thanks Jordan. I see now how a function like this can actually help me a lot. Often my validations lead to a function, and sometimes those have more validations. I'll play with these kind of constructions and see if i can improve the code!

– Jonathan
Nov 20 '18 at 0:56

*Joran! want to get your name right.

– Jonathan
Nov 20 '18 at 1:12

add a comment |

you can abstract it out to a generic validated input method

def validated_input(prompt,validation_method,error_message):

    while True:

         result = input(prompt)

         if validation_method(result):

            return result

         print(error_message)





choices = ['red','green','blue','none']

validator = lambda test:test.lower().strip() in choices

prompt = "Enter A Color(one of Red, Green, Blue, or None):"

error_message = "Please enter a valid color or None!"



print(validated_input(prompt,validator,error_message))

its arguable whether this is "better"

answered Nov 20 '18 at 0:45

Joran Beasley

72.5k678118

you can abstract it out to a generic validated input method

def validated_input(prompt,validation_method,error_message):

    while True:

         result = input(prompt)

         if validation_method(result):

            return result

         print(error_message)





choices = ['red','green','blue','none']

validator = lambda test:test.lower().strip() in choices

prompt = "Enter A Color(one of Red, Green, Blue, or None):"

error_message = "Please enter a valid color or None!"



print(validated_input(prompt,validator,error_message))

its arguable whether this is "better"

answered Nov 20 '18 at 0:45

Joran Beasley

72.5k678118

answered Nov 20 '18 at 0:45

Joran Beasley

72.5k678118

answered Nov 20 '18 at 0:45

Joran Beasley

72.5k678118

answered Nov 20 '18 at 0:45

Joran Beasley

72.5k678118

Thanks Jordan. I see now how a function like this can actually help me a lot. Often my validations lead to a function, and sometimes those have more validations. I'll play with these kind of constructions and see if i can improve the code!

– Jonathan
Nov 20 '18 at 0:56

*Joran! want to get your name right.

– Jonathan
Nov 20 '18 at 1:12

add a comment |

Thanks Jordan. I see now how a function like this can actually help me a lot. Often my validations lead to a function, and sometimes those have more validations. I'll play with these kind of constructions and see if i can improve the code!

– Jonathan
Nov 20 '18 at 0:56

*Joran! want to get your name right.

– Jonathan
Nov 20 '18 at 1:12

Thanks Jordan. I see now how a function like this can actually help me a lot. Often my validations lead to a function, and sometimes those have more validations. I'll play with these kind of constructions and see if i can improve the code!

– Jonathan
Nov 20 '18 at 0:56

*Joran! want to get your name right.

– Jonathan
Nov 20 '18 at 1:12

add a comment |

x = 0

while True:

  if x == 12:

     break;

  else:

     x = x + 1

print(x)

This will create a infinite loop until the condition you are looking for is met and then it will break out of the loop. Make sure you have your escape condition though.

answered Nov 20 '18 at 1:24

Jay Patel

261

add a comment |

x = 0

while True:

  if x == 12:

     break;

  else:

     x = x + 1

print(x)

This will create a infinite loop until the condition you are looking for is met and then it will break out of the loop. Make sure you have your escape condition though.

answered Nov 20 '18 at 1:24

Jay Patel

261

add a comment |

x = 0

while True:

  if x == 12:

     break;

  else:

     x = x + 1

print(x)

This will create a infinite loop until the condition you are looking for is met and then it will break out of the loop. Make sure you have your escape condition though.

answered Nov 20 '18 at 1:24

Jay Patel

261

x = 0

while True:

  if x == 12:

     break;

  else:

     x = x + 1

print(x)

This will create a infinite loop until the condition you are looking for is met and then it will break out of the loop. Make sure you have your escape condition though.

answered Nov 20 '18 at 1:24

Jay Patel

261

answered Nov 20 '18 at 1:24

Jay Patel

261

answered Nov 20 '18 at 1:24

Jay Patel

261

answered Nov 20 '18 at 1:24

Jay Patel

261

add a comment |

draft saved

draft discarded

Thanks for contributing an answer to Stack Overflow!

Please be sure to answer the question. Provide details and share your research!

But avoid …

Asking for help, clarification, or responding to other answers.

Making statements based on opinion; back them up with references or personal experience.

To learn more, see our tips on writing great answers.

draft saved

draft discarded

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Post as a guest

Name

Required, but never shown

Post as a guest

Name

Required, but never shown

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Post as a guest

Name

Required, but never shown

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Post as a guest

Name

Required, but never shown

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Post as a guest

Name

Required, but never shown

Name

Required, but never shown

Name

Required, but never shown

This page is only for reference, If you need detailed information, please check here

Search This Blog

Ufyukyu