CODEWITHSUNDEEP
pythonpython-2.7
ayl
ayl

Reputation: 394

Python list index out of range on return value of split

I'm writing a simple script that is trying to extract the first element from the second column of a .txt input file. 

import sys

if (len(sys.argv) > 1):
    f = open(sys.argv[1], "r");
    print "file opened";

line = [];

for line in f:
    line = line.strip("\n ' '")
    line = line.split(",") 
    print line[1]

f.close();

My input file looks like this:

Client 192.168.1.13 said ``ACC: d0bb38f18da536aff7b455264eba2f1e35dd976f,389182.567,-0.042,-0.893,0.333''
Client 192.168.1.13 said ``ACC: d0bb38f18da536aff7b455264eba2f1e35dd976f,389182.590,-0.036,-0.905,0.273''
Client 192.168.1.13 said ``ACC: d0bb38f18da536aff7b455264eba2f1e35dd976f,389182.611,-0.046,-0.948,0.204''
Client 192.168.1.13 said ``ACC: d0bb38f18da536aff7b455264eba2f1e35dd976f,389182.631,-0.074,-0.978,0.170''
Client 192.168.1.13 said ``ACC: d0bb38f18da536aff7b455264eba2f1e35dd976f,389182.654,-0.100,-1.006,0.171''

I want my delimiter to be a comma. When I print the length of the line out, I'm getting 5 elements (as expected). However, whenever I try to index the list to extract the data (i.e., when I call print line[1]), I keep getting the following error:

file opened
Traceback (most recent call last):
  File "stats.py", line 13, in <module>
    print line[1]
IndexError: list index out of range

I don't understand why it's out of range when clearly it isn't.

Upvotes: 8

Views: 53679

Answers (4)

John La Rooy
John La Rooy

Reputation: 304137

It can be useful to catch the exception an print the offending lines

for line in f:
    line = line.strip("\n ' '")
    line = line.split(",") 
    try:
        print line[1]
    except IndexError, e:
        print e
        print "line =", line
        raise   # if you don't wish to continue

Upvotes: 0

Samy Vilar
Samy Vilar

Reputation: 11120

you probably have empty line(s) after your data, I ran your test code without them it worked as expected.

$ python t.py t.txt
file opened
389182.567
389182.590
389182.611
389182.631
389182.654

if you don't want to remove them, then simply check for empty lines.

for line in f:
    if line.strip(): # strip will remove all leading and trailing whitespace such as '\n' or ' ' by default    
        line = line.strip("\n ' '")
        line = line.split(",") 
        print line[1]

Upvotes: 2

Levon
Levon

Reputation: 143047

I would guess you have a blank line somewhere in your file. If it runs through the data and then generates the exception the blank line will be at the end of your file.

Please insert 

print len(line), line

before your 

print line[1]

as a check to verify if this is the case.

You can always use this construct to test for blank lines and only process/print non-blank lines:

for line in f:
    line = line.strip()
    if line:
       # process/print line further

Upvotes: 9

pyfunc
pyfunc

Reputation: 66709

When you are working with list and trying to get value at particular index, it is always safe to see in index is in the range

if len(list_of_elements) > index: 
   print list_of_elements[index]

See:

>>> list_of_elements = [1, 2, 3, 4]
>>> len(list_of_elements)
4
>>> list_of_elements[1]
2
>>> list_of_elements[4]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: list index out of range
>>>

Now you have to find out why your list did not contain as many elements as you expected

Solution:

import sys

if (len(sys.argv) > 1):
    f = open(sys.argv[1], "r")
    print "file opened"

for line in f:
    line = line.strip().strip('\n')
    # Ensure that you are not working on empty line
    if line:
        data = line.split(",") 
    # Ensure that index is not out of range
    if len(data) > 1: print data[1]

f.close()

Upvotes: 3

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