Extracting patterns after matching a regex

Mart. mdekauwe at gmail.com
Wed Sep 9 11:01:09 CEST 2009


On Sep 8, 4:33 pm, MRAB <pyt... at mrabarnett.plus.com> wrote:
> Mart. wrote:
> > On Sep 8, 3:53 pm, MRAB <pyt... at mrabarnett.plus.com> wrote:
> >> Mart. wrote:
> >>> On Sep 8, 3:14 pm, "Andreas Tawn" <andreas.t... at ubisoft.com> wrote:
> >>>>>>> Hi,
> >>>>>>> I need to extract a string after a matching a regular expression. For
> >>>>>>> example I have the string...
> >>>>>>> s = "FTPHOST: e4ftl01u.ecs.nasa.gov"
> >>>>>>> and once I match "FTPHOST" I would like to extract
> >>>>>>> "e4ftl01u.ecs.nasa.gov". I am not sure as to the best approach to the
> >>>>>>> problem, I had been trying to match the string using something like
> >>>>>>> this:
> >>>>>>> m = re.findall(r"FTPHOST", s)
> >>>>>>> But I couldn't then work out how to return the "e4ftl01u.ecs.nasa.gov"
> >>>>>>> part. Perhaps I need to find the string and then split it? I had some
> >>>>>>> help with a similar problem, but now I don't seem to be able to
> >>>>>>> transfer that to this problem!
> >>>>>>> Thanks in advance for the help,
> >>>>>>> Martin
> >>>>>> No need for regex.
> >>>>>> s = "FTPHOST: e4ftl01u.ecs.nasa.gov"
> >>>>>> If "FTPHOST" in s:
> >>>>>>     return s[9:]
> >>>>>> Cheers,
> >>>>>> Drea
> >>>>> Sorry perhaps I didn't make it clear enough, so apologies. I only
> >>>>> presented the example  s = "FTPHOST: e4ftl01u.ecs.nasa.gov" as I
> >>>>> thought this easily encompassed the problem. The solution presented
> >>>>> works fine for this i.e. re.search(r'FTPHOST: (.*)',s).group(1). But
> >>>>> when I used this on the actual file I am trying to parse I realised it
> >>>>> is slightly more complicated as this also pulls out other information,
> >>>>> for example it prints
> >>>>> e4ftl01u.ecs.nasa.gov\r\n', 'FTPDIR: /PullDir/0301872638CySfQB\r\n',
> >>>>> 'Ftp Pull Download Links: \r\n', 'ftp://e4ftl01u.ecs.nasa.gov/PullDir/
> >>>>> 0301872638CySfQB\r\n', 'Down load ZIP file of packaged order:\r\n',
> >>>>> etc. So I need to find a way to stop it before the \r
> >>>>> slicing the string wouldn't work in this scenario as I can envisage a
> >>>>> situation where the string lenght increases and I would prefer not to
> >>>>> keep having to change the string.
> >>>> If, as Terry suggested, you do have a tuple of strings and the first element has FTPHOST, then s[0].split(":")[1].strip() will work.
> >>> It is an email which contains information before and after the main
> >>> section I am interested in, namely...
> >>> FINISHED: 09/07/2009 08:42:31
> >>> MEDIATYPE: FtpPull
> >>> MEDIAFORMAT: FILEFORMAT
> >>> FTPHOST: e4ftl01u.ecs.nasa.gov
> >>> FTPDIR: /PullDir/0301872638CySfQB
> >>> Ftp Pull Download Links:
> >>>ftp://e4ftl01u.ecs.nasa.gov/PullDir/0301872638CySfQB
> >>> Down load ZIP file of packaged order:
> >>>ftp://e4ftl01u.ecs.nasa.gov/PullDir/0301872638CySfQB.zip
> >>> FTPEXPR: 09/12/2009 08:42:31
> >>> MEDIA 1 of 1
> >>> MEDIAID:
> >>> I have been doing this to turn the email into a string
> >>> email = sys.argv[1]
> >>> f = open(email, 'r')
> >>> s = str(f.readlines())
> >> To me that seems a strange thing to do. You could just read the entire
> >> file as a string:
>
> >>      f = open(email, 'r')
> >>      s = f.read()
>
> >>> so FTPHOST isn't the first element, it is just part of a larger
> >>> string. When I turn the email into a string it looks like...
> >>> 'FINISHED: 09/07/2009 08:42:31\r\n', '\r\n', 'MEDIATYPE: FtpPull\r\n',
> >>> 'MEDIAFORMAT: FILEFORMAT\r\n', 'FTPHOST: e4ftl01u.ecs.nasa.gov\r\n',
> >>> 'FTPDIR: /PullDir/0301872638CySfQB\r\n', 'Ftp Pull Download Links: \r
> >>> \n', 'ftp://e4ftl01u.ecs.nasa.gov/PullDir/0301872638CySfQB\r\n', 'Down
> >>> load ZIP file of packaged order:\r\n',
> >>> So not sure splitting it like you suggested works in this case.
>
> > Within the file are a list of files, e.g.
>
> > TOTAL FILES: 2
> >            FILENAME: MOD13A2.A2007033.h17v08.005.2007101023605.hdf
> >            FILESIZE: 11028908
>
> >            FILENAME: MOD13A2.A2007033.h17v08.005.2007101023605.hdf.xml
> >            FILESIZE: 18975
>
> > and what i want to do is get the ftp address from the file and collect
> > these files to pull down from the web e.g.
>
> > MOD13A2.A2007033.h17v08.005.2007101023605.hdf
> > MOD13A2.A2007033.h17v08.005.2007101023605.hdf.xml
>
> > Thus far I have
>
> > #!/usr/bin/env python
>
> > import sys
> > import re
> > import urllib
>
> > email = sys.argv[1]
> > f = open(email, 'r')
> > s = str(f.readlines())
> > m = re.findall(r"MOD....\.........\.h..v..\.005\..............\....
> > \....", s)
>
> > ftphost = re.search(r'FTPHOST: (.*?)\\r',s).group(1)
> > ftpdir  = re.search(r'FTPDIR: (.*?)\\r',s).group(1)
> > url = 'ftp://' + ftphost + ftpdir
>
> > for i in xrange(len(m)):
>
> >    print i, ':', len(m)
> >    file1 = m[i][:-4]               # remove xml bit.
> >    file2 = m[i]
>
> >    urllib.urlretrieve(url, file1)
> >    urllib.urlretrieve(url, file2)
>
> > which works, clearly my match for the MOD13A2* files isn't ideal I
> > guess, but they will always occupt those dimensions, so it should
> > work. Any suggestions on how to improve this are appreciated.
>
> Suppose the file contains your example text above. Using 'readlines'
> returns a list of the lines:
>
>  >>> f = open(email, 'r')
>  >>> lines = f.readlines()
>  >>> lines
> ['TOTAL FILES: 2\n', '\t\tFILENAME:
> MOD13A2.A2007033.h17v08.005.2007101023605.hdf\n', '\t\tFILESIZE:
> 11028908\n', '\n', '\t\tFILENAME:
> MOD13A2.A2007033.h17v08.005.2007101023605.hdf.xml\n', '\t\tFILESIZE:
> 18975\n']
>
> Using 'str' on that list then converts it to s string _representation_
> of that list:
>
>  >>> str(lines)
> "['TOTAL FILES: 2\\n', '\\t\\tFILENAME:
> MOD13A2.A2007033.h17v08.005.2007101023605.hdf\\n', '\\t\\tFILESIZE:
> 11028908\\n', '\\n', '\\t\\tFILENAME:
> MOD13A2.A2007033.h17v08.005.2007101023605.hdf.xml\\n', '\\t\\tFILESIZE:
> 18975\\n']"
>
> That just parsing a lot more difficult.
>
> It's much easier to just read the entire file as a single string and
> then parse that:
>
>  >>> f = open(email, 'r')
>  >>> s = f.read()
>  >>> s
> 'TOTAL FILES: 2\n\t\tFILENAME:
> MOD13A2.A2007033.h17v08.005.2007101023605.hdf\n\t\tFILESIZE:
> 11028908\n\n\t\tFILENAME:
> MOD13A2.A2007033.h17v08.005.2007101023605.hdf.xml\n\t\tFILESIZE: 18975\n'
>  >>> import re
>  >>> re.findall(r"FILENAME: (.+)", s)
> ['MOD13A2.A2007033.h17v08.005.2007101023605.hdf',
> 'MOD13A2.A2007033.h17v08.005.2007101023605.hdf.xml']

If I do it this way I can't seem to not extract the \r at the end of
the line.

In [26]: m = re.search(r"FTPHOST: (.+)", s)

In [27]: m.group(1)
Out[27]: 'e4ftl01u.ecs.nasa.gov\r'

but if I insert \\r at the end as was previously suggested.

In [28]: m = re.search(r"FTPHOST: (.+)\\r", s)

In [29]: m.group(1)

AttributeError: 'NoneType' object has no attribute 'group'

Any thoughts?

Thanks



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