On Mon, 07 Jul 2014 07:08:53 -0700, rxjwg98 wrote:
> More specific, what does 're.M' means?
Feel free to look at it interactively. re.M is a flag to control the
meaning of the regular expression. It is short for re.MULTILINE, just as
re.I is short for re.IGNORECASE:
py> import re
py> re.M == re.MULTILINE
True
py> re.I == re.IGNORECASE
True
They are just numeric flags:
py> re.I
2
py> re.M
8
so you can combine then:
py> re.I | re.M
10
re.M turns on "multi-line matching". This changes the meaning of the
special characters ^ and $.
Standard mode:
^ matches the start of the string
$ matches the end of the string
Multi-line mode:
^ matches the start of each line
$ matches the end of each line
Here is an example. Copy and paste this into the interpreter:
import re
text = """First line.
Second line.
Third line."""
pattern = "^.*$" # Match anything from the start to end.
By default, . does not match newlines, so by default the regex matches
nothing:
py> re.search(pattern, text) is None # Nothing matches!
True
If you use MULTILINE mode, $ matches the end of the first line:
py> re.search(pattern, text, re.M).group()
'First line.'
If you add MULTILINE mode and DOTALL mode, it matches everything:
py> re.search(pattern, text, re.M|re.S).group()
'First line.\nSecond line.\nThird line.'
See the reference manual for more details:
https://docs.python.org/3/library/re.html#module-contents
(Python 3)
https://docs.python.org/2/library/re.html#module-contents
(Python 2)
--
Steven
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