Replace one string in a list of strings

Question

I have a list of strings.

If one of the strings (e.g. at index 5) is the empty string, I want to replace it with "N".

How do I do that? The naive method (for a java programmer) does not work:

string_list[5] = "N"

gives

'str' object does not support item assignment

(string_list originally came from a .csv-file- that is why it might contain empty strings.)

Looks like `string_list` is actually a string, not a list of strings. Lists are mutable, so you should be able to replace its item just like you did. — Kos, Aug 23 '12 at 08:40
You have simple string not list, and you can use replace method. — Denis, Aug 23 '12 at 08:40
I need to look at my code again and explain better. Give me a sec. — The Unfun Cat, Aug 23 '12 at 08:47

score 5 · Accepted Answer · answered Aug 23 '12 at 08:41

Your error seems to indicate that your string_list is not a list of string but a real string (that doesn't support assignement because a string is immutable).

If your string_list was a real list of strings, like this for example : string_list = ["first", "second", "", "fourth"], then you will be able to do string_list[2] = "third" to obtain string_list = ["first", "second", "third", "fourth"].

If you need to automatically detect where an empty string is located in your list, try with index :

string_list[string_list.index("")] = "replacement string"

print string_list
>>> ["first", "second", "replacement string", "fourth"]

I made a dumdum mistake: when splitting my original line I gave it an index so a string was returned, not a list. *Feeling embarrased* — The Unfun Cat, Aug 23 '12 at 08:51

score 2 · Answer 2 · answered Aug 23 '12 at 08:48

2

You say you have a list of strings but from you error it looks like you're trying to index a string

l =  ["a", "b", "", "c"]

Is a list of strings.

l = ["N" if not x else x for x in l]

Is a list of strings with empty strings replaced with "N"

answered Aug 23 '12 at 08:48

Aesthete

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Nice. Good something worthwhile came out of my mistake. – The Unfun Cat Aug 23 '12 at 08:56
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Anything for someone with a name like that. Made me laugh :) – Aesthete Aug 23 '12 at 08:58

RocketDonkey · Answer 3 · 2012-08-23T08:45:14.653

1

Try this:

>>> s = 'abc de'
>>> s.replace(' ', 'N')
'abcNde'

As mentioned by the others, it sounds like string_list is actually a string itself, meaning that you can't use assignment to change a character.

edited Aug 23 '12 at 08:45

answered Aug 23 '12 at 08:38

RocketDonkey

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@Aesthete Ha, no worries - I did too at first. – RocketDonkey Aug 23 '12 at 08:41

score 0 · Answer 4 · answered Aug 23 '12 at 08:44

In python work with lists and convert them to strings when need be.

>> str = list("Hellp")

>> str
['H', 'e', 'l', 'l', 'p']

>> str[4] = 'o'

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

TO make it a string use

>> "".join(str)

'Hello World'

Python strings are immutable and they cannot be modified.

Or you could use List Comprehensions.

Some thing like:

>> myStr = ['how', 'are', 'yew', '?']

>> myStr = [w.replace('yew', 'you') for w in myStr]

score 0 · Answer 5 · edited Jul 23 '16 at 00:13

0

The following example iterates through lists of lists (sublists), in order to replace a string, a word:

myoldlist=[['aa bbbbb'],['dd myword'],['aa myword']]
mynewlist=[]
for i in xrange(0,3,1):
    mynewlist.append([x.replace('myword', 'new_word') for x in myoldlist[i]])

print mynewlist
# ['aa bbbbb'],['dd new_word'],['aa new_word']

edited Jul 23 '16 at 00:13

Jamal

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answered Apr 29 '16 at 12:55

Estatistics

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Your two answers seem to be [almost identical](http://stackoverflow.com/questions/13781828/replace-a-string-in-list-of-lists/36938886#36938886) you probably could consider refer one as your answer while the other you simply need to post a link in the comment (once your rep is >= 50) – Ian Apr 29 '16 at 13:18

Replace one string in a list of strings

5 Answers5