Python: loop through a file for specific lines

Question

I have the following lines in a file where I want to take the third column; In the file I don't have the numbers column:

Red; Blue; Green; White; Orange;
Green; White; Orange;
Blue; Green; White;
Red; Blue; Green; White;
Blue; Green; White; Orange;
Orange
Green; White; Orange;
White; Orange
Green;

I used this code line to do that:

lines = i.split(";")[2]

The problem is that some of the lines have only one column or two, so it gives me 'index out of range' error. Please tell me how to go about this problem?

thanks a lot Adia

well, what do want to do when there isn't enough columns?

SilentGhost
– SilentGhost

2010-10-08 14:07:10 +00:00
Commented Oct 8, 2010 at 14:07 — SilentGhost
– SilentGhost, Commented Oct 8, 2010 at 14:07

Mike Clark · Accepted Answer · 2010-10-08 14:07:13Z

2

what about something like this:

cols = i.split(";")
if (len(cols) >= 3):
    lines = cols[2]
else:
    #whatever you want here

answered Oct 8, 2010 at 14:07

Mike Clark

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Comments

user395760 · Accepted Answer · 2010-10-08 14:11:15Z

2

The simple solution is to check the number of columns and ignore lines with less than three columns.

third_columns = []
with open("...") as infile:
    for line in infile:
        columns = line.split(';')
        if len(columns) >= 3:
            third_columns.append(columns[2])

And if you parse CSV (seems like you do), you better use one of the numerous existing CSV parsers, e.g. the one in the standard library.

answered Oct 8, 2010 at 14:11

user395760

Comments

aaronasterling · Accepted Answer · 2010-10-12 12:32:57Z

1

use a slice instead of an index.

>>> with open('test.txt') as f_in:
...     column3 = (line.split(';')[2:3] for line in f_in)
...     column3 = [item[0] for item in column3 if item]
... 
>>> column3
[' Green', ' Orange', ' White', ' Green', ' White', ' Orange']

edited Oct 12, 2010 at 12:32

answered Oct 8, 2010 at 14:08

aaronasterling

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Comments

ghostdog74 · Accepted Answer · 2010-10-08 14:42:23Z

0

for line in open("file"):
    try:
        s=line.split(";")[2]
    except: pass
    else:
        print s

answered Oct 8, 2010 at 14:42

ghostdog74

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