[Tutor] bubble sort function

[Danny Yoo]

> def ask_for_a_digit():
>     while True:
>         digit = raw_input("Give me a digit between 0 and 9.")
>         if digit not in "0123456789":
>             print "You didn't give me a digit.  Try again."
>         else:
>             return int(digit)


Ooops.  I made a mistake.  ask_for_a_digit() is not technically quite
right, because I forgot that when we're doing the expression:

    digit not in "0123456789"

that this is technically checking that the left side isn't a substring
of the right side.  That's not what I wanted: I intended to check for
element inclusion instead.  So there are certain inputs where the
buggy ask_for_a_digit() won't return an integer with a single digit.

Here's one possible correction:

###################################################
def ask_for_a_digit():
    while True:
        digit = raw_input("Give me a digit between 0 and 9.")
        if len(digit) != 1 or digit not in "0123456789":
            print "You didn't give me a digit.  Try again."
        else:
            return int(digit)
###################################################


My apologies for not catching the bug sooner.