CODEWITHSUNDEEP
python
user1355603
user1355603

Reputation: 305

Index error on splitting arrays

I have the following array(in python):

arr= ['\n', ' a#B\n', ' c#D\n']

Now I an trying to split on '#' for which I am writing the code given below:

 for i in arr:
 g=i.split("#")[1]

I am getting the following error:

 g=i.split("#")[1]
 IndexError: list index out of range

I am not getting why am I getting the error. Can someone be kind enough to help rectify it.

Upvotes: 0

Views: 159

Answers (4)

Levon
Levon

Reputation: 143047

The error is caused because the first split results in a list that contains only 1 element ['\n'], so the index value of [1] is out of bounds.

See:

for i in arr:
   g = i.split("#")
   print g

output:

['\n']
[' a', 'B\n']
[' c', 'D\n']

One quick way to fix it would be:

[i.split('#')[1] for i in arr if len(i.split('#')) > 1]

though it contains two calls to split().

The one below is a bit more verbose, but only calls split() once.

for i in arr:
    g = i.split('#')
    if len(g) > 1:
       g = g[1]

As @kindall suggests below in the comments, the use of partition() is an alternative to split() here too.

Upvotes: 1

bgporter
bgporter

Reputation: 36474

Others have explained why you're getting that exception. Here's an idea for a different approach that may be useful to you.

Starting with Python 2.5, string objects grew a new partition method:

str.partition(sep)

Split the string at the first occurrence of sep, and return a 3-tuple containing the part before the separator, the separator itself, and the part after the separator. If the separator is not found, return a 3-tuple containing the string itself, followed by two empty strings.

>>> arr= ['\n', ' a#B\n', ' c#D\n'] 
>>> for s in arr:
...     print s.partition('#')
... 
('\n', '', '')
(' a', '#', 'B\n')
(' c', '#', 'D\n')

You can pull the string apart without encountering an excpetion whether the separator is found or not.

Upvotes: 2

Christian Witts
Christian Witts

Reputation: 11585

The first element in your array that you iterate through has no hash # so when you call split on it, it returns only 1 item in the list as in ['\n'] so when you try to access the second item by [1] it can't find it giving you the error.

Remember, in Python indexing starts at 0, not 1.

Upvotes: 0

g.d.d.c
g.d.d.c

Reputation: 47978

When the first element of your list, '\n' is assigned to i it does not contain "#", so the result list is only one element long, not two. Attempting to retrieve index 1 fails, but index 0 would be present.

Upvotes: 2

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