Python Replace \\ with \ [duplicate]

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
– Santa, Commented Mar 3, 2011 at 21:44

Hex · Accepted Answer · 2018-06-27 12:34:53Z

58

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, 2018 at 12:34

Hex

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answered Mar 3, 2011 at 21:56

Jochen Ritzel

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6 Comments

Jonathan Hartley Over a year ago

I think the equivalent of this for Python 3 is: bytes(s, 'utf-8').decode("unicode_escape")

Mike Chamberlain Over a year ago

Alternatively in Python 3: 'a\\nb'.encode().decode('unicode_escape')

Luke Davis Over a year ago

@JonathanHartley you should submit this as a separate answer.

Jonathan Hartley Over a year ago

No, you should!

born_naked Over a year ago

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. "

|

sleeplessnerd · Accepted Answer · 2011-03-03 21:43:35Z

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 3, 2011 at 21:43

answered Mar 3, 2011 at 21:38

sleeplessnerd

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Comments

Santa · Accepted Answer · 2011-03-03 21:47:40Z

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 3, 2011 at 21:47

Santa

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2 Comments

kand Over a year ago

This worked thanks! Part of the issue was that I was confusing myself by thinking that \\n was 3 characters instead of just 2.

mlatu Over a year ago

it's worse: '\n' is just one character: 0x0d

nmichaels · Accepted Answer · 2011-03-03 21:44:00Z

2

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

or

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

answered Mar 3, 2011 at 21:44

nmichaels

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Comments

Abbafei · Accepted Answer · 2011-03-03 21:39:03Z

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 3, 2011 at 21:39

Abbafei

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Comments

Brian Goldman · Accepted Answer · 2011-03-03 21:43:57Z

1

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 '\\'
\

answered Mar 3, 2011 at 21:43

Brian Goldman

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Comments

Raj Ratn · Accepted Answer · 2021-06-17 07:54:55Z

0

In Python 3 it will be:

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

answered Jun 17, 2021 at 7:54

Raj Ratn

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Comments

Contango · Accepted Answer · 2022-05-10 10:28:45Z

-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, 2022 at 10:28

Contango

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Comments

Gaurav Agarwal · Accepted Answer · 2020-09-05 20:30:36Z

-3

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

answered Sep 5, 2020 at 20:30

Gaurav Agarwal

5

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