Python - List Index Out Of Range In For Loop

Question

I'm fairly new to python and I'm currently working on a program that will encrypt and decrypt strings. As part of it, I need the individual letters of the string to each be added to an empty list; for example, the string 'hello' would be entered into a list list like so:

['h','e','l','l','o']

The part of the code that is giving me this error can be found below. Thanks.

emptyList=[]
message=input("What Would You Like To Encrypt?\n")

messageLength=len(message)
for count in range(0,messageLength):
        emptyList=[]
        emptyList[count].append(message[count])

emptyList[0] does not exist when emptyList is []. You might want to empyList.append(message[count]). That said, it'd likely be easier to do emptyList = list(message) — inspectorG4dget
– inspectorG4dget, Commented Mar 7, 2016 at 16:51

Martijn Pieters · Accepted Answer · 2016-03-07 16:51:18Z

You are trying to address indices in an empty list:

>>> lst = []
>>> lst[0]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: list index out of range
>>> lst[0] = 1
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: list assignment index out of range

If you wanted to add elements to a list, just use list.append() directly on the list object itself to create more indices; don't create new empty lists each time:

emptyList=[]
messageLength=len(message)
for count in range(0,messageLength):
    emptyList.append(message[count])

Not that you need to be this elaborate, the following is enough:

emptyList = list(message)

list() takes any iterable and adds all the elements of that iterable to a list. Since a string is iterable, producing all the characters in that string, calling list() on a string creates a list of those characters:

>>> list('hello')
['h', 'e', 'l', 'l', 'o']

Kordi · Accepted Answer · 2016-03-07 16:58:38Z

2

Basically you want just read from the input and then output a list

Python 2.7

message=raw_input("What Would You Like To Encrypt?\n")
print list(message)

Python 3.X

message=input("What Would You Like To Encrypt?\n")
print(list(message))

Output

If you input Hello

['H', 'e', 'l', 'l', 'o']

edited Mar 7, 2016 at 16:58

answered Mar 7, 2016 at 16:53

Kordi

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