How do I verify that a string only contains letters, numbers, underscores and dashes?

Question

I know how to do this if I iterate through all of the characters in the string but I am looking for a more elegant method.

Answer 1

Regular expression can be very flexible.

import re;
re.fullmatch("^[\w-]+$", target_string) # fullmatch looks also workable for python 3.4

\w: Only [a-zA-Z0-9_]

So you need to add - char for justify hyphen char.

+: Match one or more repetitions of the preceding char. I guess you don't accept blank input. But if you do, change to * .

^: Matches the start of the string.

$: Matches the end of the string.

You need these two special characters since you need to avoid the following case. The unwanted chars like & here might appear between the matched pattern.

&&&PATTERN&&PATTERN