[Tutor] Fwd: Problem with nested for-in

Thu, 29 Jan 2009 05:39:22 -0800

Hello I hope this will be clearer


here is the script :

####################################

# -*- coding: utf-8 -*-
import csv

lines = csv.reader(open("CATEGORY.csv","r"))
lines2 = csv.reader(open("CATEGORYLIST.csv","r"))

old_cats = []
for line in lines:
    print line
    stories = []
    for line2 in lines2:
        print "\t%s == %s ? %s" % (line2[1], line[0], line2[1] == line[0])
        if line2[1] == line[0]:
            stories.append(line2[0])
    old_cats.append((line[0],line[2], stories))

####################################

here's the output :

['100701', '22', 'Water softeners', '2', '0', '100401']
21092 == 100701 ? False
100418 == 100701 ? False
100440 == 100701 ? False
100405 == 100701 ? False
100704 == 100701 ? False
21079 == 100701 ? False
21081 == 100701 ? False
21075 == 100701 ? False
21085 == 100701 ? False
21076 == 100701 ? False
21082 == 100701 ? False
21085 == 100701 ? False
21092 == 100701 ? False
100396 == 100701 ? False
100700 == 100701 ? False
100335 == 100701 ? False
100335 == 100701 ? False
100420 == 100701 ? False
100421 == 100701 ? False
100335 == 100701 ? False
100337 == 100701 ? False
['100702', '22', 'Garment processing', '2', '0', '100491']
['100703', '22', 'Fume hoods', '2', '0', '100441']
['100704', '22', 'Tank vent breathers', '2', '0', '100405']
['100705', '22', 'Absorbent paper', '2', '0', '100438']
['100706', '22', 'Packaging machinery & equipment', '2', '0', '100403']
['100707', '22', 'Copper', '2', '0', '100428']
['100708', '22', 'Silver', '2', '0', '100428']
['100709', '22', 'Clinical waste disposal', '2', '0', '100418']
['100710', '22', 'Air decontamination systems', '2', '0', '100342']
['100711', '22', 'Instrument cleaner-processors', '2', '0', '100438']
['100712', '22', 'Pathogen identification', '2', '0', '100404']
['100713', '22', 'Biocidal wipes', '2', '0', '100517']
['100714', '22', 'Medical devices', '2', '0', '100418']
['100715', '22', 'Testing', '2', '0', '100491']


when can see that the inner loop is only executed for the first item of the top-level loop...


I've attached the 2 CSV files.

Thanks

Attachment: CATEGORYLIST.csv
Description: Binary data

Attachment: CATEGORY.csv
Description: Binary data


Begin forwarded message:

From: W W <[email protected]>
Date: 29 January 2009 11:43:37 GMT
To: "emmanuel.delaborde" <[email protected]>
Subject: Re: [Tutor] Problem with nested for-in

On Thu, Jan 29, 2009 at 5:06 AM, emmanuel.delaborde <[email protected]> wrote:
Hello,

I have the following snippet :

lines = csv.reader(open("CATEGORY.csv","r"))
lines2 = csv.reader(open("CATEGORYLIST.csv","r"))

old_cats = []
for line in lines:
      print line 

   stories = []
   for line2 in lines2:
          print line2 

       if line2[1] == line[0]:
           stories.append(line2[0])
   old_cats.append((line[0],line[2], stories))


what happens is that

for the first elt of lines, the nested for in runs fine
but then never seem to run again while the top level loop iterates through the rest of lines

consequently stories accumulate nothing...

Can someone explain please ?

I would try adding the two print statements above to your code. It might give you an idea about what's going on. It would also be helpful to provide us with some of your original data and the data you get once you've run the program.

HTH,
Wayne



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