Prompt the user to input something else if the first input is invalid [duplicate]
Solution 1:
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.")