Python path and raw strings [closed]

Answer 1

My interpreter suggests that you are mistaken in your belief that the second example does not work, because

>>> r"D:\final\Res.mat" == "D:\\final\\Res.mat"
True

The correct way to build file paths from components is by using the os.path.join function, which can take multiple arguments and is portable across platforms. I would suggest you try something like

result = os.path.join(path, nameFile+".mat")

Answer 2

The r prefix is used to indicate the you want the string to be evaluated as "raw", keeping backslashes as-is.

Try this:

path = r"D:\final"
nameFile = "Res"

result = path + '\\' + nameFile + 'mat'

As you can see, I added r before the string expression that contains a non-escaped backslash.

To see the difference, try doing :

print("\\")
print(r"\\")

(Without the parentheses if you're using Python2)

Also, I recommend using the pathlib module of the standard library to handle paths properly. This will also help a lot if you try to make your code portable:

from pathlib import Path
(Path("D:/final") / path / nameFile).with_suffix('.mat')

Answer 3

You need use a raw string for the path variable, or escape the backslash:

path = r"D:\final"

You can see the difference here:

>>> "D:\final"
'D:\x0cinal'
>>> r"D:\final"
'D:\\final'

In the first case '\f' is the form feed character 0x0c.

Also, use os.path.join() to construct pathnames:

import os.path

path = r"D:\final"
nameFile = "Res.mat"

result = os.path.join(path, nameFile)
>>> result
'D:\\final\\Res'

Since you explicitly append the string literal .mat to nameFile, why not simply define nameFile with the .mat extension? If this needs to be dynamic, just add it on like this:

extension = '.mat'
result = os.path.join(path, nameFile + extension)

Answer 4

How do I get the "r" in front of the name without using " "?

Just use os.path.join:

import os

path = r"D:\final"
nameFile= "Res.mat"

result = os.path.join(path, nameFile)
print(result)
>> D:\final\Res.mat