Re: Parsing of a file

[Shawn Milochik]

>

I would like to parse this file by extracting the field id, ra, dec and mjd
for each line. It is
not, however, certain that the width of each value of the field id, ra, dec
or mjd is the same
in each line. Is there a way to do this such that even if there was a line

Regular expressions will do the trick nicely.

where Ra=****** and
MJD=******** was swapped it would be parsed correctly?

Yes, but you'll probably have to look at each line three times or
split it into a list and check the elements.

Cheers
Tommy
--
http://mail.python.org/mailman/listinfo/python-list

ShawnMilo

[Stefan Behnel]

Shawn Milochik wrote:

>I would like to parse this file by extracting the field id, ra, dec and mjd
for each line. It is
not, however, certain that the width of each value of the field id, ra, dec
or mjd is the same
in each line. Is there a way to do this such that even if there was a line

Regular expressions will do the trick nicely.

>where Ra=****** and
MJD=******** was swapped it would be parsed correctly?

Yes, but you'll probably have to look at each line three times or
split it into a list and check the elements.

You can use named groups in a single regular expression.

Stefan

[Paul McGuire]

On Aug 6, 3:14*pm, "Shawn Milochik" <[e-mail]:

Regular expressions will do the trick nicely.

Or just use str.split, and create dicts using dict(list_of_tuples)
constructor.

This code creates a single dict for the input lines, keyed by id.
Each value contains elements labeled 'id', 'ra', and 'mjd'.

-- Paul
data = """\
Field f29227: Ra=20:23:46.54 Dec=+67:30:00.0 MJD=53370.06797690
Frames 5 Set 1
Field f31448: Ra=20:24:58.13 Dec=+79:39:43.9 MJD=53370.06811620
Frames 5 Set 2
Field f31226: Ra=20:24:45.50 Dec=+78:26:45.2 MJD=53370.06823860
Frames 5 Set 3
Field f31004: Ra=20:25:05.28 Dec=+77:13:46.9 MJD=53370.06836020
Frames 5 Set 4
Field f30782: Ra=20:25:51.94 Dec=+76:00:48.6 MJD=53370.06848210
Frames 5 Set 5
Field f30560: Ra=20:27:01.82 Dec=+74:47:50.3 MJD=53370.06860400
Frames 5 Set 6
Field f30338: Ra=20:28:32.35 Dec=+73:34:52.0 MJD=53370.06872620
Frames 5 Set 7
Field f30116: Ra=20:30:21.70 Dec=+72:21:53.6 MJD=53370.06884890
Frames 5 Set 8
Field f29894: Ra=20:32:28.54 Dec=+71:08:55.0 MJD=53370.06897070
Frames 5 Set 9
Field f29672: Ra=20:34:51.89 Dec=+69:55:56.6 MJD=53370.06909350
Frames Set 10 """.splitlines()

d = dict(
(rec.split()[1][:-1],
dict([('id',rec.split()[1][:-1])] +
[map(str.lower,f.split('='))
for f in rec.split()[2:5]] ) )
for rec in data
)
print d.keys()

for id in d.keys():
print d[id].items()

[bearophileHUGS]

Paul McGuire:

This code creates a single dict for the input lines, keyed by id.
Each value contains elements labeled 'id', 'ra', and 'mjd'.

....

d = dict(
(rec.split()[1][:-1],
dict([('id',rec.split()[1][:-1])] +
[map(str.lower,f.split('='))
for f in rec.split()[2:5]] ) )
for rec in data
)

....

Please, don't try to shove the program in one line, use PyParsing :o)

Bye,
bearophile