[Tutor] better looping construct for replacing elements in file?

[Joel Goldstick]

On Thu, Feb 2, 2012 at 3:50 PM, Brett Longworth <blongworth at whoi.edu> wrote:
> Hello,
>
> Today I wrote a quick script to replace elements in multiple lines of a file
> with corresponding elements from a single line in another file, linking the
> two via an index element. The code iterates through the entire source file
> to find the matching index for each line of the destination file. This
> works, but it's clearly a terrible way to solve the problem. Can someone
> point me to a more efficient, pythonic solution?
>
> thanks,
> -Brett
>
> Code:
>
> wheel = "A794"
> wheelfile = "A794.txt"
> statusfile = "CURRENT.ams"
>
> sfile = csv.reader(open(statusfile), delimiter='\t')
> statusWriter = csv.writer(open('statustest.txt', 'wb'), delimiter='\t',
> quotechar='|', quoting=csv.QUOTE_MINIMAL)
>
> for sline in sfile:
>  #print sline
>  wfile = csv.reader(open(wheelfile))
>  for line in wfile:
>    #print line[0]
>    #print sline[18]
>    if line[0] == sline[18]:
>      sline[0] = line [1]
>      sline[1] = "OSG"+str(line[4])
>      sline[17] = wheel
>      sline[21] = line[9]
>      statusWriter.writerow(sline)
>
> Excerpt of wheelfile:
>
> "2","X496","02/01/12","OSG","106788","85411","GS-13365","Outside Primary
> Standard | > Modern (1950)","2.43","149177"
> "3","C655","02/01/12","OSG","106534","83028","HY-19231","Outside Blank | >
> 30,000","3.63","149178"
>
> Excerpt of statusfile:
>
> Y002    BET2918    10/18/06 15:32:52    160.00    174    1.000    16408
>  1.306E-12    1.213E-10    402.6    405.9    -42.7    3.2    1.2242
>  -0.0220    1.822    -12.66    A499    2    1    5631    86523    data
>  3.7E-6
> Y002    BET2918    10/18/06 15:35:46    150.00    162    1.000    15654
>  1.313E-12    1.226E-10    407.6    410.3    -43.9    2.0    1.2180
>  -0.0243    1.894    -13.03    A499    2    1    5631    86523        3.7E-6
> 0003    BET7147    10/18/06 15:55:33    170.00    186    1.000    3442
>  2.903E-13    2.693E-11    357.7    359.3    -46.1    2.5    1.2000
>  0.0276    1.734    -12.86    A499    3    1    5631    86524        3.3E-6
> 0003    BET7147    10/18/06 15:58:49    170.00    185    1.000    3232
>  2.772E-13    2.598E-11    351.8    353.4    -46.1    3.5    1.2000
>  0.0149    1.761    -12.66    A499    3    1    5631    86524        3.2E-6
> 0003    BET7147    10/18/06 16:02:06    170.00    185    1.000    3399
>  2.955E-13    2.753E-11    346.9
>
>
> --
> Brett Longworth
> Research Associate
> Woods Hole Oceanographic Institution
> ph: 508.289.3559
> fax: 508.457.2183
>
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If you are a little savvy with sql you could write each csv to tables,
Since you have csv file input why not write each to a db table.  Then
you could join on  line[0] == sline[18] and update your 4 fields.

Then dump table as csv

-- 
Joel Goldstick