Question

I have a question about regex/Python. Sorry if this topic has been discussed millions of times – usually I find the answers on so/google etc. but I’m stuck in the millions of answers with this one.. (To be honest – I own a regex book, but somehow I’m too stupid to really understand it…)

For a music-management-system I need to extract information out of paths, providing different sets of options. Here two examples:

If the path is: (Case 1)

"/The Prodigy/The Fat Of The Land/04 - Funky Stuff.flac"

it should extract:

• artist: “The Prodigy”
• release: “The Fat Of The Land”
• Tracknumber: 4
• Title: “Funky Stuff”

And for eg: (Case 2)

"/[XLR 483] The Fat Of The Land/04 - The Prodigy - The  Funky Stuff.flac"

should extract:

• catno: “XLR 483”
• release: “The Fat Of The Land”
• Tracknumber: 4
• artist: “The Prodigy”
• Title: “Funky Stuff”

There is no need for a regex that covers both cases, these are just two examples. I’ll then provide them as options (or starting-point to add own ones).

Any help would be greatly appreciated!

@ S.Lott: I don’t have a regex for this, I started with splitting the string:

parts = rel_path.split('/')       
track = parts[-1]
release = parts[-2]
artist = parts[-3]

but this looks like an extremely inflexible and un-elegant solution to me.

edit:

So far I have something like:

pattern = re.compile('^/(?P<artist>[a-zA-Z0-9 ]+)/(?P<release>[a-zA-Z0-9 ]+)/(?P<track>[a-zA-Z0-9 -_]+).[a-zA-Z]*.*')


rel_path = '/The Prodigy/The Fat Of The Land/04 - Funky Stuff.flac'

match = pattern.search(rel_path)

artist = match.group('artist')
release = match.group('release')
track = match.group('track')

Answer 1

Although not necessary, but re is handy choice for this problem.

import re
pattern = re.compile(r"/(?P<artist>[a-zA-Z0-9 ]+?)/(?P<release>[a-zA-Z0-9 ]+?)/(?P<tracknumber>\d+?) - (?P<title>[a-zA-Z0-9 ]+?).flac")
s = "/The Prodigy/The Fat Of The Land/04 - Funky Stuff.flac"
m = pattern.search(s)
print m.group('artist')
print m.group('release')
print m.group('track number')
print m.group('title')

I use expressions such as [a-zA-Z0-9 ] to explicitly specify the chars I expect in the string. It is just my preference to have a white-list-like regex to make the code more secure. There are many other ways to compose equivalent patterns. You will find all you need here http://docs.python.org/library/re.html, you don’t need a book for that.