Wsrtjtyk

I'm very new to Python, so forgive my newbish question. I have the following code:

[a while loop starts]



print 'Input the first data as 10 characters from a-f'



input1 = raw_input()

if not re.match("^[a-f]*$", input1):

    print "The only valid inputs are 10-character strings containing letters a-f"

    break

else:

[the rest of the script]

If I wanted to, instead of breaking the loop and quitting the program, send the user back to the original prompt until they input valid data, what would I write instead of break?

To go on with the next loop iteration, you can use the continue statement.

I'd usually factor out the input to a dedicated function:

def get_input(prompt):

    while True:

        s = raw_input(prompt)

        if len(s) == 10 and set(s).issubset("abcdef"):

            return s

        print("The only valid inputs are 10-character "

              "strings containing letters a-f.")

print "Input initial data.  Must be 10 characters, each being a-f."

input = raw_input()

while len(input) != 10 or not set(input).issubset('abcdef'):

    print("Must enter 10 characters, each being a-f."

    input = raw_input()

Slight alternative:

input = ''

while len(input) != 10 or not set(input).issubset('abcdef'):

    print("Input initial data.  Must enter 10 characters, each being a-f."

    input = raw_input()

Or, if you wanted to break it out in to a function (this function is overkill for this use, but an entire function for a special case is suboptimal imo):

def prompt_for_input(prompt, validate_input=None, reprompt_on_fail=False, max_reprompts=0):

    passed = False

    reprompt_count = 0

    while not (passed):

        print prompt

        input = raw_input()

        if reprompt_on_fail:

            if max_reprompts == 0 or max_reprompts <= reprompt_count:

                passed = validate_input(input)

            else:

                passed = True

        else:

            passed = True

        reprompt_count += 1

   return input

This method lets you define your validator. You would call it thusly:

def validator(input):

    return len(input) == 10 and set(input).subset('abcdef')



input_data = prompt_for_input('Please input initial data.  Must enter 10 characters, each being a-f.', validator, True)