problems with a regular expression

I'm trying to get a correct regular expressi开发者_如何学Pythonon for this problem:

I get a result from a webservice as a string that looks like this

tag: 54e16e66 (Mifare card standard)

I need to extract the 54e16e66 part (which is in hexa) only, regardless of what is before and after that part, i've tried several patterns, but I am not confident enough with regex and I can't seem to find a pattern that works.

Edit

• "tag :" is aways present.

• the hexa part I want to extract has variable length

• what is after is a user comment, so it could be anything

Could someone help ? thanks in advance ! Michael

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Assuming your string there is a good template, and assuming a posix regular expression parser,

/^tag: ([0-9a-f]{8})/

should work. If the length is variable, you would just change the {8} to {m,n}, where m and n are the minimum and maximum possible number of characters you can expect, respectively.