Python, How to replace multiple parts (in a list) of elements in a list

Question

A list of original strings:

Originals = ["nice apple", "orange", "pear sweet", "red ape"]

A list of strings to remove:

To_remove = ["nice ", " sweet"]

What I want to achieve is to remove the strings needed to be removed in each elements in the original words

result: ["apple", "orange", "pear", "red ape"]

I do following but it doesn’t produce a good result.

for t in To_remove:
    for o in Originals:
        print o.replace(t, "")

what would be the right way? Thank you.

*`but it doesn’t produce a good result`* -- **What do you see**? Please show us! — Wolf, Feb 03 '17 at 09:04
Your questions title is quite confusing, maybe you should reword it to match your actual need. — Wolf, Feb 03 '17 at 09:27
Suggestion for a catching title: **Howto "censor" a string list in python?** :-) — Wolf, Feb 03 '17 at 10:12

score 4 · Accepted Answer · edited May 23 '17 at 12:08

4

Strings are immutable. Hence, none of the methods you can call on a string does an in-place modification. They all return a new string, so you have to reassign the string returned by replace:

for t in To_remove:
    for i in range(len(Originals)):
        Originals[i] = Originals[i].replace(t, "")

You can check out this question for how to merge the replacement of multiple patterns.

edited May 23 '17 at 12:08

Community

1
1

answered Feb 03 '17 at 08:53

user2390182

72,016
6
67
89

And for just a tip and in case to use PEP8 standards: use snake case. – wencakisa Feb 03 '17 at 08:54
@Wencakisa see OP (concerning *`snake case`*) – Wolf Feb 03 '17 at 09:03
*`the return value`* -- better use the *result of the replace operation* or something like this, to make clear **what** you mean. – Wolf Feb 03 '17 at 09:20
@Wolf I added some clarification. – user2390182 Feb 03 '17 at 09:43
much better, though you provide a link to the docs of version 2, as I said: hard to google this ;) – Wolf Feb 03 '17 at 09:48

score 3 · Answer 2 · edited Feb 03 '17 at 09:21

3

Because string is immutable, you have to reassign the list element.

for t in To_remove:
    for i, o in enumerate(Originals):
        Originals[i] = o.replace(t, "")

print Originals

hope this helps.

edited Feb 03 '17 at 09:21

Wolf

9,679
7
62
108

answered Feb 03 '17 at 08:52

thangtn

856
6
7

thank you for the teaching. very good! hope you don't mind I choose the first answered for answer... – Mark K Feb 03 '17 at 09:05
I like the *`print Originals`* idea, this part is missing in the OP – Wolf Feb 03 '17 at 09:23

score 1 · Answer 3 · edited May 23 '17 at 11:45

1

You are printing the results of the replacement, but do not change the list contents. If you have a closer look on the replace method (for strings(!)), you'll see that you are not only not changing the list but also not changing the strings you are getting for o in Originals. I omit including a working example, since schwobaseggl and thangtn ^[1] already provide it.

^[1] Who was really first? The SO timestamps contradict my personal experience.

edited May 23 '17 at 11:45

Community

1
1

answered Feb 03 '17 at 09:01

Wolf

9,679
7
62
108

BTW: the [official docs](https://docs.python.org/3/library/stdtypes.html#str.replace) are very sparse, maybe this is the reason you have so bad Google results for it. – Wolf Feb 03 '17 at 09:42

score 1 · Answer 4 · edited Feb 03 '17 at 17:56

1

Originals = ["nice apple", "orange", "pear sweet", "red ape"]
To_remove = ["nice ", " sweet"]
result = []

for o in Originals:
    for t in To_remove:
        result.append(o.replace(t, ""))

print result

Is that what you need?

edited Feb 03 '17 at 17:56

Wolf

9,679
7
62
108

answered Feb 03 '17 at 09:28

Dev Jalla

1,910
2
13
21

Some more text may help to understand the purpose of the repetition of the already known. – Wolf Feb 03 '17 at 09:37
...I have to correct myself about this (concerning *'repetition'*) you don't an in-place replacement. A valid option. – Wolf Feb 03 '17 at 17:58

Python, How to replace multiple parts (in a list) of elements in a list

4 Answers4