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How can I check if a Python string at any point has a single space before new line? And if it does, I have to remove that single space, but keep the new line symbol. Is this possible?

  • Just to clarify, you're talking about strings like `'my test string'`, `'my test string '`, and `'my test string \n`, right? And you want to turn them into either `'my test string'` or `'my test string\n'`? – TigerhawkT3 Mar 17 '15 at 23:20
  • @TigerhawkT3 I want to check if a Python string at any point has a single space before new line? And if it does, I have to remove that single space, but keep the new line symbol. Is this possible? –  Mar 17 '15 at 23:23
  • Okay; my answer should take care of that. – TigerhawkT3 Mar 17 '15 at 23:25
  • @TigerhawkT3 There are a few problems. Strings might have only one character in them, so doing something like string[-2] would be out of bounds. –  Mar 17 '15 at 23:28
  • What if that one character is a space? – TigerhawkT3 Mar 17 '15 at 23:53
  • did you want to replace the space before last newline character with empty string? – Avinash Raj Mar 18 '15 at 00:59
  • So you want strings that end with two spaces to end with one space after this script runs? – ideasman42 Jul 23 '17 at 11:51

4 Answers4

3
def remspace(my_str):
    if len(my_str) < 2: # returns ' ' unchanged
        return my_str
    if my_str[-1] == '\n':
        if my_str[-2] == ' ':
            return my_str[:-2] + '\n'
    if my_str[-1] == ' ':
        return my_str[:-1]
    return my_str

Results:

>>> remspace('a b c')
'a b c'
>>> remspace('a b c ')
'a b c'
>>> remspace('a b c\n')
'a b c\n'
>>> remspace('a b c \n')
'a b c\n'
>>> remspace('')
''
>>> remspace('\n')
'\n'
>>> remspace(' \n')
'\n'
>>> remspace(' ')
' '
>>> remspace('I')
'I'
TigerhawkT3
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  • str[-2] might be out of bounds though. I'm looking at a are variety of strings. Some of them may even be something like: "I\n" –  Mar 17 '15 at 23:27
  • This is really close. The string may also be something like: "I" –  Mar 17 '15 at 23:36
  • How about if the string is `' '`, a single space? `if len(str) > 1 and str[-1] == ' ':` rather than `if str[-1] == ' ':` results in returning the single space. If you prefer that it turn `' '` into the empty string, use the latter. – TigerhawkT3 Mar 17 '15 at 23:36
  • Please don't use `str`... when I see it - all I can think is the builtin `str`... call it `text` or something - shadowing a built-in name is never good practice :( – Jon Clements Mar 17 '15 at 23:51
  • Funny story: I was consciously attempting to avoid using `string`, and blundered right into `str`. – TigerhawkT3 Mar 17 '15 at 23:55
  • @TigerhawkT3 been there done that... at least `string` is slightly better - as it's more likely someone wants to use `str` than the `string` module... but six of one, half dozen of the other etc... – Jon Clements Mar 17 '15 at 23:57
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    Well, I'm sure that `my_str` is available - after all, I clearly scrawled "MINE!" on it. – TigerhawkT3 Mar 18 '15 at 00:01
  • @ninja_power: this code was for the original, unedited question that specified the end of the string. To handle `' \n'` appearing anywhere in the string, use `my_str.replace(' \n', '\n')` as per Malonge's answer. – TigerhawkT3 Mar 18 '15 at 00:20
2

How about just replacing the specific instance of ' \n' with '\n'?

s1 = 'This is a test \n'
s1.replace(' \n', '\n') 
>>> 'This is a test\n'

s2 = 'There is no trailing space here\n'
s2.replace(' \n', '\n')
>>> 'There is no trailing space here\n'
Malonge
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0

If you want to strip multiple spaces, you can use regex:

import re

def strip_trailing_space(my_string):
    return re.sub(r' +(\n|\Z)', r'\1', my_string)

def strip_trailing_whitespace(my_string):
    return re.sub(r'[ \t]+(\n|\Z)', r'\1', my_string)
ideasman42
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0

Input File:

filea.txt (With many spaces)

dragon
dragonballs

test.py

filea = open('filea.txt','r')
fileb = open('fileb.txt','a')
for line in filea:
for i in range(len(line)):
if ' \n' in line:
line = line.replace(' \n','\n')
fileb.write(line)

op:

fileb.txt

dragon
dragonballs

DK_2022
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    As it’s currently written, your answer is unclear. Please [edit] to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers [in the help center](/help/how-to-answer). – Community Feb 22 '22 at 14:49