无法在 Python 中打开文本文件 3：Unicode 错误

Question

I am having a problem open a simple text file in Python 3.8. I setup a simple test.

Here is my test code:

import os

file_path = "c:\Users\username\Documents\folder1\some_file.txt"

with open(file_path, 'r') as f:
    for line in f:
        print(line)

I get the following error: Unicode Error "unicodeescape" codec can't decode bytes in position 2-3.

I have read other posts about putting an 'r' in front of the file path and when I do I get an "No such file or directory: 'c:\Users\username\Documents\folder1\some_file.txt'

import os

file_path = r"c:\Users\username\Documents\folder1\some_file.txt"

with open(file_path, 'r') as f:
    for line in f:
        print(line)

I have also tried using double backslash in the path c:\\Users\\username\\Documents\\folder1\\some_file.txt and that did not work either.

I have tried a test using pathlib and still get unicode error.

from pathlib import Path

file_path = "c:\Users\username\Documents\folder1\some_file.txt"

file_path = Path(file_path).absolute()

with open(fpath, 'r', encoding='utf-8') as f:
    line = f.readlines()
    for line in f:
        print(line)

Answer 1

In your first example, file_path = "c:\Users\username\Documents\folder1\some_file.txt" The \U in \Users represents a Unicode escape sequence and it is trying to decode sers as a Unicode character, which it is not.

On my machine, the double backslash seems to work - but of course I do not have a text file at that path so I can not really test.

Try first the double backslash for just the \U.

Answer 2

Further information:

As Andrew Kaluzniacki's answer rightly pointed out, the trouble was with the path string.

Using pathlib.Path

To prevent hassle with Windows paths and delimiters, one could opt to always use forward slashes, as both open() and Windows have mechanisms of handling this.

However, for the sake of backward compatibility and robustness it is arguably better to use pathlib.Path from the standard library (still using forward slashes as path separators). pathlib automatically converts the filepath to one suited to your OS.

Lastly, os.path.filesep() returns the file separator for the host OS.

Another potential cause for people having a similar issue

There may be a character in the file not covered by your operating system's default encoding.

Try other encodings by passing a different encoding to the encoding parameter of open() .

You could try open(file_path, 'r', encoding='utf-8') , although that should be the default for Windows 10, assuming that is your OS based on you filepath examples.

Without knowing what is in the file, it is hard to know which encoding would work, however.

from pathlib import Path

fpath = Path(fpath).absolute()
# ^^ absolute() is not necessary if
# the file is in the same directory
# as the calling Python script
# and you just pass a filename.

with open(fpath, 'r', encoding='utf-8') as filehandle:
    do_something_with(filehandle)