Python regex match

Question

I am trying to match a text in a file

In [44]: with open(path) as f:
   ....:     for line in f:
   ....:         matched = re.search('^PARTITION BY HASH',line)
   ....:         if matched is not None:
   ....:             print matched.group()
   ....:

The file contains lines like PARTITION BY HASH(SOME_THING); And also some other lines among which there is SUBPARTITION BY HASH(SOME_THING) which shouldn't be matched

After the match i would like to delete that line. But the print matched.group fails why ?

why re here? just do if "PARTITION BY HASH" in line or if line.startswith("PARTITION BY HASH"): — Ashwini Chaudhary
– Ashwini Chaudhary, Commented Nov 6, 2012 at 10:17

Ashwini Chaudhary · Accepted Answer · 2012-11-06 10:32:07Z

1

something like this:

In [29]: strs1="PARTITION BY HASH(SOME_THING)"

In [30]: strs2="SUBPARTITION BY HASH(SOME_THING)"

In [31]: bool(re.match(r"^PARTITION BY HASH",strs1))
Out[31]: True

In [32]: bool(re.match(r"^PARTITION BY HASH",strs2))
Out[32]: False

answered Nov 6, 2012 at 10:32

Ashwini Chaudhary

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Comments

cooltea · Accepted Answer · 2012-11-06 10:51:27Z

But the print matched.group fails

Well it simply does what it is supposed to do: it returns the match. In this case since

>>> import re
>>> line = "PARTITION BY HASH(something)"
>>> re.search('^PARTITION BY HASH', line).group()
'PARTITION BY HASH'

If you want to print the lines that start with 'PARTITION BY HASH', based on what Ashwini Chaudhary suggested:

with open(path) as f:
    for line in f:
        if line.startswith('PARTITION BY HASH'):
            print line,

Please note the comma to prevent print from inserting an additional end-of-line characters.

If you insist on using the package re

import re

with open(path) as f:
    for line in f:
        if re.match('PARTITION BY HASH', line):
            print line,

Please note the usage of re.match without the starting position indicator ^ (see http://docs.python.org/2/library/re.html#search-vs-match for more information)

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