[Tutor] Fwd: Problem with nested for-in

[emmanuel.delaborde]

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



Begin forwarded message:

> From: W W <srilyk at gmail.com>
> Date: 29 January 2009 11:43:37 GMT
> To: "emmanuel.delaborde" <emmanuel.delaborde at cimex.com>
> Cc: tutor at python.org
> Subject: Re: [Tutor] Problem with nested for-in
>
> On Thu, Jan 29, 2009 at 5:06 AM, emmanuel.delaborde <emmanuel.delaborde at cimex.com 
> > 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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