Python Replace \\ with \

Question

So I can't seem to figure this out... I have a string say, "a\\nb" and I want this to become "a\nb". I've tried all the following and none seem to work;

>>> a
'a\\nb'
>>> a.replace("\\","\")
  File "<stdin>", line 1
    a.replace("\\","\")
                      ^
SyntaxError: EOL while scanning string literal
>>> a.replace("\\",r"\")
  File "<stdin>", line 1
    a.replace("\\",r"\")
                       ^
SyntaxError: EOL while scanning string literal
>>> a.replace("\\",r"\\")
'a\\\\nb'
>>> a.replace("\\","\\")
'a\\nb'

I really don't understand why the last one works, because this works fine:

>>> a.replace("\\","%")
'a%nb'

Is there something I'm missing here?

EDIT I understand that \ is an escape character. What I'm trying to do here is turn all \\n \\t etc. into \n \t etc. and replace doesn't seem to be working the way I imagined it would.

>>> a = "a\\nb"
>>> b = "a\nb"
>>> print a
a\nb
>>> print b
a
b
>>> a.replace("\\","\\")
'a\\nb'
>>> a.replace("\\\\","\\")
'a\\nb'

I want string a to look like string b. But replace isn't replacing slashes like I thought it would.

Your original string, `a = 'a\\nb'` does not actually have two `'\'` characters, the first one is an escape for the latter. If you do, `print a`, you'll see that you actually have only one `'\'` character. — Santa, Mar 03 '11 at 21:44

score 57 · Accepted Answer · edited Jun 27 '18 at 12:34

57

There's no need to use replace for this.

What you have is a encoded string (using the string_escape encoding) and you want to decode it:

>>> s = r"Escaped\nNewline"
>>> print s
Escaped\nNewline
>>> s.decode('string_escape')
'Escaped\nNewline'
>>> print s.decode('string_escape')
Escaped
Newline
>>> "a\\nb".decode('string_escape')
'a\nb'

In Python 3:

>>> import codecs
>>> codecs.decode('\\n\\x21', 'unicode_escape')
'\n!'

edited Jun 27 '18 at 12:34

Scott Martin

1,260
2
17
27

answered Mar 03 '11 at 21:56

Jochen Ritzel

104,512
31
200
194

6

I think the equivalent of this for Python 3 is: `bytes(s, 'utf-8').decode("unicode_escape")` – Jonathan Hartley May 08 '11 at 21:56
3

Alternatively in Python 3: `'a\\nb'.encode().decode('unicode_escape')` – Mike Chamberlain Feb 22 '12 at 14:01
1

@JonathanHartley you should submit this as a separate answer. – Luke Davis Jan 01 '18 at 02:50
No, you should! – Jonathan Hartley Jan 03 '18 at 16:32
This won't remove the double slash in all cases, for instance \\N will fail. print(codecs.decode('\\N\\x21', 'unicode_escape')) w/error message "malformed \N character escape. " – born_naked Jun 18 '21 at 19:09
as mentioned by @born_naked, this does not remove the double slash in all cases. It is not a general solution specially for recent python versions. – David Nov 16 '22 at 23:20

sleeplessnerd · Answer 2 · 2011-03-03T21:43:35.803

13

You are missing, that \ is the escape character.

Look here: http://docs.python.org/reference/lexical_analysis.html at 2.4.1 "Escape Sequence"

Most importantly \n is a newline character. And \\ is an escaped escape character :D

>>> a = 'a\\\\nb'
>>> a
'a\\\\nb'
>>> print a
a\\nb
>>> a.replace('\\\\', '\\')
'a\\nb'
>>> print a.replace('\\\\', '\\')
a\nb

edited Mar 03 '11 at 21:43

answered Mar 03 '11 at 21:38

sleeplessnerd

21,853
1
25
29

score 3 · Answer 3 · answered Mar 03 '11 at 21:44

3

r'a\\nb'.replace('\\\\', '\\')

or

'a\nb'.replace('\n', '\\n')

answered Mar 03 '11 at 21:44

nmichaels

49,466
12
107
135

score 3 · Answer 4 · answered Mar 03 '11 at 21:47

3

Your original string, a = 'a\\nb' does not actually have two '\' characters, the first one is an escape for the latter. If you do, print a, you'll see that you actually have only one '\' character.

>>> a = 'a\\nb'
>>> print a
a\nb

If, however, what you mean is to interpret the '\n' as a newline character, without escaping the slash, then:

>>> b = a.replace('\\n', '\n')
>>> b
'a\nb'
>>> print b
a
b

answered Mar 03 '11 at 21:47

Santa

11,381
8
51
64

This worked thanks! Part of the issue was that I was confusing myself by thinking that \\n was 3 characters instead of just 2. – kand Mar 03 '11 at 23:22
it's worse: '\n' is just one character: 0x0d – mlatu Dec 13 '22 at 23:02

score 1 · Answer 5 · answered Mar 03 '11 at 21:39

1

It's because, even in "raw" strings (=strings with an r before the starting quote(s)), an unescaped escape character cannot be the last character in the string. This should work instead:

'\\ '[0]

answered Mar 03 '11 at 21:39

Abbafei

3,088
3
27
24

score 1 · Answer 6 · answered Mar 03 '11 at 21:43

In Python string literals, backslash is an escape character. This is also true when the interactive prompt shows you the value of a string. It will give you the literal code representation of the string. Use the print statement to see what the string actually looks like.

This example shows the difference:

>>> '\\'
'\\'
>>> print '\\'
\

score 0 · Answer 7 · answered Jun 17 '21 at 07:54

0

In Python 3 it will be:

bytes(s, 'utf-8').decode("unicode_escape")

answered Jun 17 '21 at 07:54

Raj Ratn

109
1
5

score -1 · Answer 8 · answered May 10 '22 at 10:28

-1

This works on Windows with Python 3.x:

import os
str(filepath).replace(os.path.sep, '/')

Where: os.path.sep is \ on Windows and / on Linux.

Case study

Used this to prevent errors when generating a Markdown file then rendering it to pdf.

answered May 10 '22 at 10:28

Contango

76,540
58
260
305

score -2 · Answer 9 · answered Sep 05 '20 at 20:30

path = "C:\\Users\\Programming\\Downloads"
# Replace \\ with a \ along with any random key multiple times
path.replace('\\', '\pppyyyttthhhooonnn')
# Now replace pppyyyttthhhooonnn with a blank string
path.replace("pppyyyttthhhooonnn", "")

print(path)

#Output... C:\Users\Programming\Downloads

Python Replace \\ with \

9 Answers9

Case study

Linked