Remove trailing newline from the elements of a string list
Question:
I have to take a large list of words in the form:
['thisn', 'isn', 'an', 'listn', 'ofn', 'wordsn']
and then using the strip function, turn it into:
['this', 'is', 'a', 'list', 'of', 'words']
I thought that what I had written would work, but I keep getting an error saying:
“‘list’ object has no attribute ‘strip'”
Here is the code that I tried:
strip_list = []
for lengths in range(1,20):
strip_list.append(0) #longest word in the text file is 20 characters long
for a in lines:
strip_list.append(lines[a].strip())
Answers:
You can either use a list comprehension
my_list = ['thisn', 'isn', 'an', 'listn', 'ofn', 'wordsn']
stripped = [s.strip() for s in my_list]
or alternatively use map()
:
stripped = list(map(str.strip, my_list))
In Python 2, map()
directly returned a list, so you didn’t need the call to list. In Python 3, the list comprehension is more concise and generally considered more idiomatic.
list comprehension?
[x.strip() for x in lst]
You can use lists comprehensions:
strip_list = [item.strip() for item in lines]
Or the map
function:
# with a lambda
strip_list = map(lambda it: it.strip(), lines)
# without a lambda
strip_list = map(str.strip, lines)
This can be done using list comprehensions as defined in PEP 202
[w.strip() for w in ['thisn', 'isn', 'an', 'listn', 'ofn', 'wordsn']]
All other answers, and mainly about list comprehension, are great. But just to explain your error:
strip_list = []
for lengths in range(1,20):
strip_list.append(0) #longest word in the text file is 20 characters long
for a in lines:
strip_list.append(lines[a].strip())
a
is a member of your list, not an index. What you could write is this:
[...]
for a in lines:
strip_list.append(a.strip())
Another important comment: you can create an empty list this way:
strip_list = [0] * 20
But this is not so useful, as .append
appends stuff to your list. In your case, it’s not useful to create a list with defaut values, as you’ll build it item per item when appending stripped strings.
So your code should be like:
strip_list = []
for a in lines:
strip_list.append(a.strip())
But, for sure, the best one is this one, as this is exactly the same thing:
stripped = [line.strip() for line in lines]
In case you have something more complicated than just a .strip
, put this in a function, and do the same. That’s the most readable way to work with lists.
If you need to remove just trailing whitespace, you could use str.rstrip()
, which should be slightly more efficient than str.strip()
:
>>> lst = ['thisn', 'isn', 'an', 'listn', 'ofn', 'wordsn']
>>> [x.rstrip() for x in lst]
['this', 'is', 'a', 'list', 'of', 'words']
>>> list(map(str.rstrip, lst))
['this', 'is', 'a', 'list', 'of', 'words']
my_list = ['thisn', 'isn', 'an', 'listn', 'ofn', 'wordsn']
print([l.strip() for l in my_list])
Output:
['this', 'is', 'a', 'list', 'of', 'words']
You can loop through your list and simply replace n
with empty space ""
without appending it to the new list
main_list = ['thisn', 'isn', 'an', 'listn', 'ofn', 'wordsn']
for i in range(0, len(main_list)):
main_list[i] = main_list[i].replace("n", "")
Using this method you can perform multilple replacements at the same time.
Replacing n
with empty space ""
and replacing sample_text
string with the ""
for each element of the main_list
main_list = ['thisnsample_text', 'isnsample_text', 'ansample_text', 'listnsample_text', 'ofnsample_text', 'wordsnsample_text']
for i in range(0, len(main_list)):
main_list[i] = main_list[i].replace("n", "").replace("sample_text", "")
I have to take a large list of words in the form:
['thisn', 'isn', 'an', 'listn', 'ofn', 'wordsn']
and then using the strip function, turn it into:
['this', 'is', 'a', 'list', 'of', 'words']
I thought that what I had written would work, but I keep getting an error saying:
“‘list’ object has no attribute ‘strip'”
Here is the code that I tried:
strip_list = []
for lengths in range(1,20):
strip_list.append(0) #longest word in the text file is 20 characters long
for a in lines:
strip_list.append(lines[a].strip())
You can either use a list comprehension
my_list = ['thisn', 'isn', 'an', 'listn', 'ofn', 'wordsn']
stripped = [s.strip() for s in my_list]
or alternatively use map()
:
stripped = list(map(str.strip, my_list))
In Python 2, map()
directly returned a list, so you didn’t need the call to list. In Python 3, the list comprehension is more concise and generally considered more idiomatic.
list comprehension?
[x.strip() for x in lst]
You can use lists comprehensions:
strip_list = [item.strip() for item in lines]
Or the map
function:
# with a lambda
strip_list = map(lambda it: it.strip(), lines)
# without a lambda
strip_list = map(str.strip, lines)
This can be done using list comprehensions as defined in PEP 202
[w.strip() for w in ['thisn', 'isn', 'an', 'listn', 'ofn', 'wordsn']]
All other answers, and mainly about list comprehension, are great. But just to explain your error:
strip_list = []
for lengths in range(1,20):
strip_list.append(0) #longest word in the text file is 20 characters long
for a in lines:
strip_list.append(lines[a].strip())
a
is a member of your list, not an index. What you could write is this:
[...]
for a in lines:
strip_list.append(a.strip())
Another important comment: you can create an empty list this way:
strip_list = [0] * 20
But this is not so useful, as .append
appends stuff to your list. In your case, it’s not useful to create a list with defaut values, as you’ll build it item per item when appending stripped strings.
So your code should be like:
strip_list = []
for a in lines:
strip_list.append(a.strip())
But, for sure, the best one is this one, as this is exactly the same thing:
stripped = [line.strip() for line in lines]
In case you have something more complicated than just a .strip
, put this in a function, and do the same. That’s the most readable way to work with lists.
If you need to remove just trailing whitespace, you could use str.rstrip()
, which should be slightly more efficient than str.strip()
:
>>> lst = ['thisn', 'isn', 'an', 'listn', 'ofn', 'wordsn']
>>> [x.rstrip() for x in lst]
['this', 'is', 'a', 'list', 'of', 'words']
>>> list(map(str.rstrip, lst))
['this', 'is', 'a', 'list', 'of', 'words']
my_list = ['thisn', 'isn', 'an', 'listn', 'ofn', 'wordsn']
print([l.strip() for l in my_list])
Output:
['this', 'is', 'a', 'list', 'of', 'words']
You can loop through your list and simply replace n
with empty space ""
without appending it to the new list
main_list = ['thisn', 'isn', 'an', 'listn', 'ofn', 'wordsn']
for i in range(0, len(main_list)):
main_list[i] = main_list[i].replace("n", "")
Using this method you can perform multilple replacements at the same time.
Replacing n
with empty space ""
and replacing sample_text
string with the ""
for each element of the main_list
main_list = ['thisnsample_text', 'isnsample_text', 'ansample_text', 'listnsample_text', 'ofnsample_text', 'wordsnsample_text']
for i in range(0, len(main_list)):
main_list[i] = main_list[i].replace("n", "").replace("sample_text", "")