Question

pt=[2]
pt[0]=raw_input()

when i do this , and give an input suppose 1011 , it says list indexing error- ” list assignment index out of range” . may i know why? i think i am not able to assign a list properly . how to assign an array of 2 elements in python then?

Answer 1

Try this:

pt = list()
pt.append(raw_input())
pt.append(raw_input())
print pt

You now have two elements in your list. Once you are more familiar with python syntax, you might write this as:

pt = [raw_input(), raw_input()]

Also, note that lists are not to be confused with arrays in Java or C: Lists grow dynamically. You don’t have to declare the size when you create a new list.

BTW: I tried out your example in the interactive shell. It works, but probably not as you expected:

>>> pt = [2]
>>> pt[0] = raw_input()
1011
>>> pt
['1011']

I’m guessing you thought pt = [2] would create a list of length 2, so a pt[1] = raw_input() would fail like you mentioned:

>>> pt = [2]
>>> pt[0] = raw_input()
1011
>>> pt[1] = raw_input() # this is an assignment to an index not yet created.
1012
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: list assignment index out of range

Actually, pt = [2] creates a list with one element, having the value 2 at index 0:

>>> pt = [2]
>>> pt
[2]
>>>

So you can assign to the index 0 as demonstrated above, but assigning to index 1 will not work – use append for appending to a list.