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

[Brett Longworth]

Hi Joel,

Thanks for the reply. The little voice in my head was yelling, "Easier 
with SQL!" the entire time, but I'm trying to learn Python.

-Brett

On 2/2/2012 4:16 PM, Joel Goldstick wrote:
> 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
>


-- 
Brett Longworth
Research Associate
Woods Hole Oceanographic Institution
ph: 508.289.3559
fax: 508.457.2183