split a string at every nth occurrence of a delimiter (here, a pipe) in Python

gistfile1.py

import re

s = 'id|tag1|id|tag2|id|tag3|id|tag4'

# nb: escaping | (delimiter) necessary *outside* of character set ( [] ), not inside
print re.findall("[^|]+\|[^|]+", s)
# ['id|tag1', 'id|tag2', 'id|tag3', 'id|tag4']


n=3
print re.findall("\|".join(["[^|]+"]*n), s)
# ['id|tag1|id', 'tag2|id|tag3']