用re.sub删除换行符

Question

Why is the result 'bc' and not 'abc'?:

>>> import re
>>> re.sub('-\n([a-z])', '','-\nabc',re.M)
'bc'

Answer 1

re.sub replace matched pattern with replacement string. ([az]) here is also matched, so it gets removed. To avoid this, you can use look ahead syntax:

import re
re.sub('-\n(?=[a-z])', '','-\nabc',re.M)
# 'abc'

Answer 2

You can just specify the string to be replaced:

re.sub('-\\n', '','-\\nabc')

will return just the abc