Python - using list() and manipulating lists

Question

I seem to have a problem with my list generating script. I'm trying to convert a string into a list of string-lists, in order to use it in a specific fonction.

For exemple I want to convert the string 'abc' to a : [['a'],['b'],['c']]. so the script i wrote was:

s='some string'
t=[[0]]*len(s)
for i in range(len(s)):
    t[i][0] = list(s)[i]
return t

the problem is that this returns [['g'],['g'],..,['g']] instead of [['s'],['o'],..,['g']).

I found another way to achieve that, but i can't seem to find the problem of this script. So,if anyone could help me, i would really appreciate it. Thanks in advance.

I see, thank you guys :).

Hjouji Anas
– Hjouji Anas

2016-07-31 13:03:47 +00:00
Commented Jul 31, 2016 at 13:03 — Hjouji Anas
– Hjouji Anas, Commented Jul 31, 2016 at 13:03

Graham · Accepted Answer · 2017-09-27 05:41:55Z

5

[[0]] * len(s) doesn't do what you think it does, consider this better approach:

s = 'abc'
li = [[ch] for ch in s]
print(li)
>> [['a'], ['b'], ['c']]

edited Sep 27, 2017 at 5:41

Graham

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answered Jul 31, 2016 at 12:56

DeepSpace

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1 Comment

idjaw Over a year ago

You can add a condition in your comprehension to ignore whitespace too in order to just have all non-whitespace characters. But I guess it also depends on what characters are expected to be kept in the list.

Julien · Accepted Answer · 2016-07-31 13:02:24Z

3

This is a classic mistake: [[0]]*n creates a list of n references to a unique object [0]. Use this instead to create a list of n different objects all equal to [0]: [[0] for i in range(n)]. This way, you can then change the value of each of them without affecting the others.

edited Jul 31, 2016 at 13:02

answered Jul 31, 2016 at 12:56

Julien

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