How to get rid of double backslash in python windows file path string?

Question

I have a dictionary:

my_dictionary = {"058498":"table", "064165":"pen", "055123":"pencil"}

I iterate over it:

for item in my_dictionary:
    PDF = r'C:\Users\user\Desktop\File_%s.pdf' %item
    doIt(PDF)

def doIt(PDF):
    part = MIMEBase('application', "octet-stream")
    part.set_payload( open(PDF,"rb").read() )

But I get this error:

IOError: [Errno 2] No such file or directory: 'C:\\Users\\user\\Desktop\\File_055123.pdf'

It can't find my file. Why does it think there are double backslashes in file path?

There is just a single backslash. You're seeing the string representation. The file doesn't exist. — Tim Pietzcker, Aug 12 '12 at 18:36
The double backslash is not wrong, python prints/represents it that to the user way. If `a = r'raw s\tring'` and `b = 'raw s\\tring'` (no 'r' and explicit double slash) then they are both represented as `'raw s\\tring'`. — aneroid, Aug 12 '12 at 18:37

aneroid · Accepted Answer · 2018-11-21T00:05:11.143

24

The double backslash is not wrong, python represents it way that to the user. In each double backslash \\, the first one escapes the second to imply an actual backslash. If a = r'raw s\tring' and b = 'raw s\\tring' (no 'r' and explicit double slash) then they are both represented as 'raw s\\tring'.

>>> a = r'raw s\tring'
>>> b = 'raw s\\tring'
>>> a
'raw s\\tring'
>>> b
'raw s\\tring'

For clarification, when you print the string, you'd see it as it would get used, like in a path - with just one backslash:

>>> print(a)
raw s\tring
>>> print(b)
raw s\tring

And in this printed string case, the \t doesn't imply a tab, it's a backslash \ followed by the letter 't'.

Otherwise, a string with no 'r' prefix and a single backslash would escape the character after it, making it evaluate the 't' following it == tab:

>>> t = 'not raw s\tring'  # here '\t' = tab
>>> t
'not raw s\tring'
>>> print(t)  # will print a tab (and no letter 't' in 's\tring')
not raw s       ring

So in the PDF path+name:

>>> item = 'xyz'
>>> PDF = r'C:\Users\user\Desktop\File_%s.pdf' % item
>>> PDF         # the representation of the string, also in error messages
'C:\\Users\\user\\Desktop\\File_xyz.pdf'
>>> print(PDF)  # "as used"
C:\Users\user\Desktop\File_xyz.pdf

More info about escape sequences in the table here. Also see __str__ vs __repr__.

edited Nov 21 '18 at 00:05

answered Aug 12 '12 at 18:48

aneroid

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there's no `d`: `'C:\\Users\\user\\Desktop\\File_055123.pdf'` – Ashwini Chaudhary Aug 12 '12 at 19:00
Probably been edited out now. – aneroid Aug 13 '12 at 16:49
39

Sorry but this was not a helpful answer. So if double slashes are the case, then how does one fix it???? – DeeWBee Jul 06 '16 at 19:34
@DeeWBee added some clarification about escape sequences and str vs repr. – aneroid Nov 21 '18 at 00:09
1

@DeeWBee: You don't. There is nothing to fix. It's already fine. – user2357112 Nov 21 '18 at 00:11
Why is everyone hardcoding their paths? – Timothy Pulliam Nov 02 '20 at 22:12

Ashwini Chaudhary · Answer 2 · 2014-03-03T09:29:09.600

12

Double backslashes are due to r, raw string:

r'C:\Users\user\Desktop\File_%s.pdf' ,

It is used because the \ might escape some of the characters.

>>> strs = "c:\desktop\notebook"

>>> print strs                #here print thinks that \n in \notebook is the newline char
c:\desktop
otebook

>>> strs = r"c:\desktop\notebook"  #using r'' escapes the \
>>> print strs

c:\desktop\notebook

>>> print repr(strs)   #actual content of strs
'c:\\desktop\\notebook'

edited Mar 03 '14 at 09:29

answered Aug 12 '12 at 18:37

Ashwini Chaudhary

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In above example, if you display `strs` like `>>> strs` you should get `c:\\desktop\\notebook`. print doesnt show the escaped i.e. double slash \\ – Jul 08 '15 at 10:24

score 4 · Answer 3 · answered May 30 '17 at 05:18

save yourself from getting a headache you can use other slashes as well. if you know what I saying. the opposite looking slashes.

you're using now PDF = 'C:\Users\user\Desktop\File_%s.pdf' %item

try to use **

PDF = 'C:/Users/user/Desktop/File_%s.pdf' %item

** it won't be treated as a escaping character .

score 3 · Answer 4 · answered Aug 12 '12 at 18:39

It doesn't. Double backslash is just the way of the computer of saying backslash. Yes, I know this sounds weird, but think of it this way - in order to represent special characters, backslash was chosen as an escaping character (e.g. \n means newline, and not the backslash character followed by the n character). But what happens if you actually want to print (or use) a backslash (possibly followed by more characters), but you don't want the computer to treat it as an escaping character? In that case we escape the backslash itself, meaning we use a double backslash so the computer will understand it's a single backslash.

It's done automatically in your case because of the r you added before the string.

score -1 · Answer 5 · edited Dec 04 '17 at 14:58

alwbtc @ I dare say: "I found the bug..."

replace

PDF = r'C:\Users\user\Desktop\File_%s.pdf' %item
doIt(PDF)`

with

for item in my_dictionary:
    PDF = r'C:\Users\user\Desktop\File_%s.pdf' % mydictionary[item]
    doIt(PDF)`

in fact you were really looking for File_pencil.pdf (not File_055123.pdf). You were sliding the index dictionary not its contents. This forum topic maybe a side-effect.

How to get rid of double backslash in python windows file path string?

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