How can I put an actual backslash in a string literal (not use it for an escape sequence)?

Question

I have this code:

import os
path = os.getcwd()
final = path +'\xulrunner.exe ' + path + '\application.ini'
print(final)

I want output like:

C:\Users\me\xulrunner.exe C:\Users\me\application.ini

But instead I get an error that looks like:

SyntaxError: (unicode error) 'unicodeescape' codec can't decode bytes in position 0-1: truncated \xXX escape

I don't want the backslashes to be interpreted as escape sequences, but as literal backslashes. How can I do it?

---

_{Note that if the string should only contain a backslash - more generally, should have an odd number of backslashes at the end - then raw strings cannot be used. See How can I print a single backslash?. If you want to avoid the need for escape sequences, see How to write string literals in Python without having to escape them?.}

Archespore

See also Windows path in Python if you are trying to make a string with a file path in it on Windows. – Tirade

There is a reasonably good overview of escape sequences here, although that question isn't actually good quality - the underlying problem described by OP isn't actually anything to do with the escape sequences. – Tirade

See also: python: SyntaxError: EOL while scanning string literal – Tirade

See also: How to fix "<string> DeprecationWarning: invalid escape sequence" in Python? – Tirade

Answer 1

To answer your question directly, put r in front of the string.

final= path + r'\xulrunner.exe ' + path + r'\application.ini'

More on Python's site here

Both string and bytes literals may optionally be prefixed with a letter 'r' or 'R'; such strings are called raw strings and treat backslashes as literal characters

But a better solution would be os.path.join:

final = (os.path.join(path, 'xulrunner.exe') + ' ' +
         os.path.join(path, 'application.ini'))

(I split this across two lines for readability, but you could put the whole thing on one line if you want.)

I will mention that you can use forward slashes in file paths, and Python will automatically convert them to the correct separator (backslash on Windows) as necessary. So

final = path + '/xulrunner.exe ' + path + '/application.ini'

should work. But it's still preferable to use os.path.join because that makes it clear what you're trying to do.

Ellswerth

Python does not convert / into `, rather /` is a valid path separator on Windows – Powe

Note that Windows can also be able to use forward slashes instead of backslashes in general; Python doesn't need to convert them. – Aldis

@DavidHeffernan your comment is a bit messed up, looks like you were trying to use backticks around a backslash. That doesn't work for the same reason it gives Python trouble, SO's markdown considers it an escape to take the next character literally. I've learned to put a space after the backslash. – Loraine

Answer 2

You can escape the slash. Use \\ and you get just one slash.

Selfimmolation

Answer 3

You can escape the backslash with another backslash (\\), but it won’t look nicer. To solve that, put an r in front of the string to signal a raw string. A raw string will ignore all escape sequences, treating backslashes as literal text. It cannot contain the closing quote unless it is preceded by a backslash (which will be included in the string), and it cannot end with a single backslash (or odd number of backslashes).

Millihenry

Answer 4

Another simple (and arguably more readable) approach is using string raw format and replacements like so:

import os
path = os.getcwd()
final = r"{0}\xulrunner.exe {0}\application.ini".format(path)
print(final)

or using the os path method (and a microfunction for readability):

import os

def add_cwd(path):
    return os.path.join( os.getcwd(), path )

xulrunner = add_cwd("xulrunner.exe")
inifile = add_cwd("application.ini")
# in production you would use xulrunner+" "+inifile
# but the purpose of this example is to show a version where you could use any character
# including backslash
final = r"{} {}".format( xulrunner, inifile )
print(final)

Debbi