IndexError: list index out of range and python

Question

I'm telling my program to print out line 53 of an output. Is this error telling me that there aren't that many lines and therefore can not print it out?

Answer 1

If you have a list with 53 items, the last one is thelist[52] because indexing starts at 0.

IndexError

• Attribution to Real Python: Understanding the Python Traceback - IndexError

The IndexError is raised when attempting to retrieve an index from a sequence (e.g. list, tuple), and the index isn’t found in the sequence. The Python documentation defines when this exception is raised:

Raised when a sequence subscript is out of range. (Source)

Here’s an example that raises the IndexError:

test = list(range(53))
test[53]

---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
<ipython-input-6-7879607f7f36> in <module>
      1 test = list(range(53))
----> 2 test[53]

IndexError: list index out of range

The error message line for an IndexError doesn’t provide great information. See that there is a sequence reference that is out of range and what the type of the sequence is, a list in this case. That information, combined with the rest of the traceback, is usually enough to help quickly identify how to fix the issue.

Answer 2

Yes,

You are trying to access an element of the list that does not exist.

MyList = ["item1", "item2"]
print MyList[0] # Will work
print MyList[1] # Will Work
print MyList[2] # Will crash.

Have you got an off-by-one error?

Answer 3

The way Python indexing works is that it starts at 0, so the first number of your list would be [0]. You would have to print[52], as the starting index is 0 and therefore line 53 is [52].

Subtract 1 from the value and you should be fine. :)

Answer 4

Yes. The sequence doesn't have the 54th item.

Answer 5

That's right. 'list index out of range' most likely means you are referring to n-th element of the list, while the length of the list is smaller than n.

Answer 6

Always keep in mind when you want to overcome this error, the default value of indexing and range starts from 0, so if total items is 100 then l[99] and range(99) will give you access up to the last element.

whenever you get this type of error please cross check with items that comes between/middle in range, and insure that their index is not last if you get output then you have made perfect error that mentioned above.

Answer 7

If you read a list from text file, you may get the last empty line as a list element. You can get rid of it like this:

list.pop()
for i in list:
   i[12]=....

Answer 8

In Python, indexing starts at 0. Therefore, if you have a list with 53 items, list[52] will be the last item in the list.