Index Error from Python Loop

Question

For some reason I keep getting index out of range error for the following code! All I want to do is compare the next data item to current one to check redundancy.

count =  0
for row2 in data2:
    count = count +1
    if data2[count][0]!=row2[0]:
       data3.append(row2)

how many items are in your data2?

danidee
– danidee

2015-04-22 19:54:37 +00:00
Commented Apr 22, 2015 at 19:54 — danidee
– danidee, Commented Apr 22, 2015 at 19:54

Padraic Cunningham · Accepted Answer · 2015-04-22 20:11:17Z

3

Then you should loop in all but the last element of data2 as follows:

for row2 in data2[:-1]:

A more compact version for your code is:

for i,j in zip(data2[:-1], data2[1:]):
    if i!=j:
       data3.append(i)

Even more compact:

data3 = [i for i,j in zip(data2[:-1], data2[1:]) if i!=j]

Or use itertools.islice and izip to avoid creating new lists:

from itertools import islice, izip

print [i for i, j in izip(islice(data2, None, len(data2) - 2), islice(data2, 1, None)) if i != j]

Use zip if using python3.

edited Apr 22, 2015 at 20:11

Padraic Cunningham

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answered Apr 22, 2015 at 19:54

sshashank124

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3 Comments

Padraic Cunningham Over a year ago

might as well go all out and use a list comp ;)

Padraic Cunningham Over a year ago

Or use itertools to avoid building more lists print [i for i,j in izip(islice(data2,None,len(data2)-1),islice(data2, 1,None)) if i != j]

sshashank124 Over a year ago

@PadraicCunningham, You should post these as answer so you get credit for them. If not, you are more than welcome to improve my answer. Thanks

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