How to clean some some strings in the list?

Question

I am trying to remove some strings from a list when the string starts with or contains "@", "#", "http" or "rt". A sample list is below.

text_words1 = ['@football', 'haberci', '#sorumlubenim', 'dedigin', 'tarafsiz', 'olurrt', '@football', 'saysaniz', 'olur', '#sorumlubenim', 'korkakligin', 'sonu']

According to above list, I want to remove '@football' and '#sorumlubenim'. I tried the code below.

 i = 0
 while i < len(text_words1):
     if text_words1[i].startswith('@'):
         del text_words1[i] 
     if text_words1[i].startswith('#'):
         del text_words1[i] 
     i = i+1
 print 'The updated list is: \n', text_words1

However, the code above only removed some strings, not all of the ones which start with "@" or "#" symbols.

Then, I added the code below into what is above as not all strings of interest start with "@", "#" or "http", but contains those symbols.

 while i < len(text_words1):
     if text_words1[i].__contains__('@'):
         del text_words1[i] 
     if text_words1[i].__contains__('#'):
         del text_words1[i]
     if text_words1[i].__contains__('http'):
        del text_words1[i]
     i = i+1
 print 'The updated list: \n', text_words1

The above code removed some items which contains "#: or "@" but not all.

Can someone advise me how to remove all items which starts with or contain "@", "#", "http", or "rt"?

skip the `i = i + 1` when you `del text_words1[i]` in one of your if clauses, because deleting will move the index of the next string to the position of the deleted word. Best to use an `if - elif - elif - else`-structure for this with `i = i + 1` in the `else` condition — avk, Jun 03 '15 at 18:44
Yes as mentioned above don't change list while iterating. Please read this for better understanding http://stackoverflow.com/questions/1637807/modifying-list-while-iterating — James Sapam, Jun 03 '15 at 18:48

Daniel · Accepted Answer · 2015-06-03T18:54:51.190

4

As the comments point out. With your approach you lose reference of the lists' indexes therefore not iterating the whole list. You can use a list comprehension to remove the words you don't need

new_list  = [i for i in text_words1 if not i.startswith(('@','#'))]

edited Jun 03 '15 at 18:54

answered Jun 03 '15 at 18:47

Daniel

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```starts with or contains "@", "#", "http", "rt"? ``` – wwii Jun 03 '15 at 18:55

fenceop · Answer 2 · 2015-06-04T12:53:48.257

Here is my solution:

import re
text_words1 = ['@football', 'haberci', '#sorumlubenim', 'dedigin', 'tarafsiz', 'olurrt', '@football', 'saysaniz', 'olur', '#sorumlubenim', 'korkakligin', 'sonu']
for i, word in reversed(list(enumerate(text_words1))):
    if re.search('(@|#|http|rt)', word):
        del text_words1[i]

With a list comprehension:

text_words1 = [w for w in text_words1 if not re.search('(@|#|http|rt)', w)]

Note that I'm using re.search because it checks for a match anywhere in the string, whereas re.match checks for a match only at the beginning of the string. This is important because you want to remove words that begin with and/or contain those characters.

The problem with your code snippet is that you're removing items while iterating. len(text_words1) won't allow you to examine every list item because of this. Add a print statement to your while loop and you will see what I mean.

How to clean some some strings in the list?

2 Answers2