change backslash into slash in a path

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change backslash into slash in a path - paul18fr - Jul-21-2022

Hi

Typically in a Windows path, I want to change the special "backslash" character to "slash" one. I was thinking re.sub substitutes all occurences but whatever I've tested so far, it fails (same result using replace()): what I'm missing?

Path = 'D:\My Directory1\bin'
NewPath = re.sub(r'(\\)', '/', Path)
print(f"New path = {NewPath}")

(of course the number of "\" can change)

leading to:

Output:
New path = D:/My Directoryin

Thanks

Paul

RE: change backslash into slash in a path - deanhystad - Jul-21-2022

Your problem starts with

Path = 'D:\My Directory1\bin'

Path does not contain the string "\b". "\b" is an escape sequence for the back space character, so "Directory1\bin" is really "Directoryin". The substitution of "\b" with backspace has already happened before you try to replace or substitute. Your attempts fail because there is no backslash to replace.

To fix the problem you have to fix the str. Use "\\" if you want the str to contain "\" as a character, or use raw strings.

path = r'D:\My Directory1\bin'
path = 'D:\\My Directory1\\bin'

Of possible interest "\M" is just a str with a backslash followed by "M". This is because "\M" is not a recognized escape sequence like \b, \f, \n, \o, \r, \t, \u, \x

RE: change backslash into slash in a path - paul18fr - Jul-21-2022

Thanks deanhystad for your answer.

I agree with you, but the goal here is to directly rewrite a path in a good format when an external user copy/paste it from Windows; I was thinking that a basic instruction ever exists (replace or re.sub / etc), and I've done tests accordingly, but all failed.

Humm I guess it'll be necessary to write my own function to do that ...

Thanks

Paul

RE: change backslash into slash in a path - deanhystad - Jul-21-2022

If the user enters a string containing "\" it will be a backslash, and not interpreted as an escape sequence.

These all do what you want to do

import re

path = r'D:\My Directory1\bin'
print("using replace", path.replace("\\", "/"))
print("using replace with raw string", path.replace(r"\ "[0], "/"))
print("using regex", re.sub('\\\\', '/', path))

Output:using replace D:/My Directory1/bin
using replace with raw string D:/My Directory1/bin
using regex D:/My Directory1/bin

Notice the funny code needed to get around Python not allowing any kind of string literal (even a raw string) to end with a single backslash.
But if you are using this to get a file path from a user, I would use the pathlib. This code lets me use "/" or "\".

import pathlib

path = pathlib.Path(input("Filename "))
print(path)

RE: change backslash into slash in a path - paul18fr - Jul-21-2022

I played with "replace()" but it didn't worked wheareas your snippets are fine; I don't know what I did ? Huh

Thanks for you support

RE: change backslash into slash in a path - deanhystad - Jul-21-2022

(Jul-21-2022, 11:41 AM)paul18fr Wrote: I played with "replace()" but it didn't worked wheareas your snippets are fine; I don't know what I did ?

Thanks for you support

Your example did not work because the \b in Path was a backspace. There was not a backslash to replace. If you tried replace() on a string entered using input() it should have worked (assuming you used "\\" as the target string).

RE: change backslash into slash in a path - paul18fr - Jul-21-2022

Yes I understand, but there's also another difference: you've add the "r" in front of the string to declare a "regular expression" whereas in my case I'm using a variale: how can I use a variable or how can I declare the variable as a regular expression?

path = 'D:\My Directory1\bin'
Var = r''+ path   #Var = r'' + str(path)
print("using replace", Var.replace('\\', '/'))
print("using replace with raw string", path.replace(r"\ "[0], "/"))
print("using regex", re.sub('\\\\', '/', path))

(obviously it does not work because of \b as it has ever been sugested)

RE: change backslash into slash in a path - deanhystad - Jul-21-2022

There is no need to replace "\" with "/". str objects never contain escape sequences. A backslash in a string is just a backslash. Escape sequences only exist in string literals, strings that are hardcoded in your program.

This program's problem happened when the Python code is compiled.

path = "D:\My Directory1\bin"  # Contains escape sequence \b
print(path, path.replace("\b", r"\b"))

Output:
D:\My Directoryin D:\My Directory1\bin

When Python compiled "Path = 'D:\My Directory1\bin'" it converted the "\b" to a backspace character (ASCII control character BS). The resulting string was 'D:\My Directory1<BS>in' where <BS> is the backspace character. At no point does the path str include a "\b" escape sequence, so it would be impossible to replace the "\b" with "/b". The path str does include a backspace character and you can replace that character a "\b" string. There is no reason to do this, but it is possible.

Thing learned here:
1. You cannot replace escape sequences in a str object because str objects do not contain escape sequences.
2. Escape sequences are converted to characters when Python compiles your program.
3. You don't have to worry about backslashes in input strings. In a str a backslash is just a backslash.