[Tutor] Input

[Ricardo Aráoz]

Last week someone had an issue with raw_input() and how to get input for
a number. So I remembered my CP/M times and got to think of a little
function I had there. The function is lost and my time is scarce but I
made a little effort and here you have the results. It has loads of room
for improvement and probably a few bugs but it's a starting point, and
it should guarantee that you get the input you need.
You just define your mask and the functions checks the input
accordingly, it returns a string.
You might improve it by displaying the mask, e.g. for mask = '9999.99'
you might see in the screen ____.__ or for mask = '999-AAA::9999' you'd
see ___-___::___ so the user will know the format of what's expected of
him, also a beep on incorrect entry might prove nice.

HTH

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import msvcrt

_validChars = {
                'X' :
'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890'
                , '9' : '1234567890'
                , '-' : '-1234567890'
                , 'A' :
'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ'
                , '!' : 'ABCDEFGHIJKLMNOPQRSTUVWXYZ'}
_validKeys = _validChars.keys()

def maskInput(mask, separators = True) :
    lmask = list(mask)
    lmask.reverse()
    usedMask = []
    retInput = ''
    c = ''
    maskChar = lmask.pop()
    try :
        while maskChar not in _validKeys :
            if separators :
                retInput += maskChar
            msvcrt.putch(maskChar)
            maskChar = lmask.pop()
    except IndexError : pass

    c = msvcrt.getch()
    while c != chr(13) :
        if maskChar and maskChar not in _validKeys and c in
_validChars[lmask[-1]] :
            if separators :
                retInput += maskChar
            msvcrt.putch(maskChar)
            usedMask.append(maskChar)
            maskChar = lmask.pop()
        if usedMask and c == '\b' :
            try :
                if maskChar :
                    lmask.append(maskChar)
                maskChar = usedMask.pop()
                retInput = retInput[:-1]
                msvcrt.putch(c)
                msvcrt.putch(' ')
                msvcrt.putch(c)
                while usedMask[-1] not in _validKeys :
                    if maskChar :
                        lmask.append(maskChar)
                    maskChar = usedMask.pop()
                    if separators :
                        retInput = retInput[:-1]
                    msvcrt.putch(c)
                    msvcrt.putch(' ')
                    msvcrt.putch(c)
            except IndexError : pass
        elif maskChar and c in _validChars[maskChar] :
            retInput += c
            msvcrt.putch(c)
            try :
                usedMask.append(maskChar)
                maskChar = lmask.pop()
              #  while maskChar not in _validKeys :
            except IndexError :
                maskChar = ''
        c = msvcrt.getch()
    return retInput

if __name__ == '__main__' :
    invar = maskInput('-9999.99')
    print
    print invar

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