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Currently I am writing some validation code for an input in my program and I cannot seem to get the error message to display correctly!

I have my types defined in a string list like this:

types = ['Guitar','Piano','Drums','Violin','Voice','Flute','Cello','Bass']

Then my code for the validation check is:

 typevalid = False while typevalid == False: Type = input("Please enter the tutor type: ").title() for count in range (0,7): if Type == types[count]: typevalid = True Tutor = (Name,Type) insert_data(Tutor) print("New data added") print() if Type != types[count]: print("!!Please enter a correct type!!\n") add = input("Do you wish to add another record? (y/n) ")

I have tried changing and moving the second if Type code and it either repeats the error X amount of times becuase of the range loop or it will display the error message twice.

Any suggestions on how I can get this to work?

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  • Can you please explain your problem more clearly? Commented Jan 10, 2014 at 14:13
  • @thefourtheye Well my error message is either display 7 times into the code as an error or displaying twice once in the loop and once outside the loop. I am trying to find the error in my code to stop this happening and if there is an easier way of coding the validation Commented Jan 10, 2014 at 14:17

3 Answers 3

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A few suggestions:

types = ["guitar", "piano", ...] # note case while True: type_ = str(input("Please enter the tutor type: ")) if type_.lower() in types: # checks all items in types in one line break # leave while loop print("Please enter a correct type!") # only happens once per loop

You can add your other functionality around this core logic. If you want the leading capital letters back later, you can use type_.capitalize().

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Thank you that has helped a lot! Using both yours and Luke's code I have gotten in to work! Thanks!
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a couple of problems - types has 8 elements but your for loop goes over range(0,7). Better to rewrite as for count in range(len(types)):

More significantly, your second if statement doesn't work - it checks one Type each time (either in the loop or out of the loop). What you need to do is check that none have been found. Try this:

typevalid = False while typevalid == False: Type = input("Please enter the tutor type: ").title() for count in range(len(types)): if Type == types[count]: typevalid = True Tutor = (Name,Type) insert_data(Tutor) print("New data added") print() if typevalid == False: print("!!Please enter a correct type!!\n") add = input("Do you wish to add another record? (y/n) ")

NB: Just seen jonrsharpe's response - it's much cleaner but this may explain what's going wrong in your current code.

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Yes that did explain what was going wrong and now I am kicking myself as I completely forgot to use len! Using both yours and jonrsharpe's code I have gotten in to work! Thanks!
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You never break out of the loop:

for count in range(0,7): if Type == types[count]: # need to add the following lines: typevalid == True break

A few additional suggestions:

  • Rather than looping over types manually, use the builtin membership checking functionality of in

    • Do if Type in types: instead of for count in range(...

    • Better yet, since you are checking types over and over again, it's much more efficient to use a set: set(['Guitar', 'Piano', ...]), or (in Python 2.7+) simply {'Guitar', 'Piano', ... }.

  • Uppercase variables are conventionally used for class names in python. You should use lower case names instead. If you want to avoid overriding the builtin type variable, use a trailing underscore (type_), or simply make your variable more descriptive (e.g. tutor_type)

After these suggestions, your code would look something like this:

tutor_types = {'guitar', 'piano', 'drums', 'violin', 'voice', 'flute', 'cello', 'bass'} while True: tutor_type = input('Please enter the tutor type: ').lower() if tutor_type in tutor_types: # Valid input logic here break # don't forget to break out of the loop print('The error message the user receives after entering incorrect info!')
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