Question

I have multiple line string that I’d like to replace, but don’t understand why it’s not working. For some reason, a period in the string stops the matching for the regular expression.

My string:

s = """
[some_previous_text]
<start>
one_period .
<end>
[some_text_after]
"""

What I’d like to end up with:

s = """
[some_previous_text]
foo
[some_text_after]
"""

What I initially tried, but it doesn’t match anything:

>>> import re
>>> s = "<start>\none_period .\n<end>"
>>> print re.sub("<start>[^.]*<end>", "foo", s)
<start>
one_period .
<end>

However, when I took the period out, it worked fine:

>>> import re
>>> s = "<start>\nno_period\n<end>"
>>> print re.sub("<start>[^.]*<end>", "foo", s)
foo

Also, when I put an <end> tag before the period, it matched the first <end> tag:

>>> import re
>>> s = "<start>\n<end>\none_period .\n<end>"
>>> print re.sub("<start>[^.]*<end>", "foo", s)
foo
one_period .
<end>

So what’s going on here? Why does the period stop the [^.]* matching?

EDIT:

SOLVED

I mistakenly thought that the carat ^ was for new-line matching. What I needed was a re.DOTALL flag (as indicated by Amber). Here’s the expression I’m now using:

>>> import re
>>> s = "<start>\none_period .\n<end>"
>>> print re.sub("<start>.*<end>", "foo", s, flags=re.DOTALL)
foo

Answer 1

Why wouldn’t it? [^.] is “the set of all characters that is not a .” and thus doesn’t match periods.

---

Perhaps you instead meant to just put .* (any number of any characters) instead of [^.]*?

For matching across newlines, specify re.DOTALL:

re.sub("<start>.*<end>", "foo", s, flags=re.DOTALL)