Sridhar Ratnakumar Sridhar Ratnakumar - 4 months ago 46
Python Question

shutil.rmtree fails on Windows with 'Access is denied'

In Python, when running

shutil.rmtree
over a folder that contains a read-only file, the following exception is printed:

File "C:\Python26\lib\shutil.py", line 216, in rmtree
rmtree(fullname, ignore_errors, onerror)
File "C:\Python26\lib\shutil.py", line 216, in rmtree
rmtree(fullname, ignore_errors, onerror)
File "C:\Python26\lib\shutil.py", line 216, in rmtree
rmtree(fullname, ignore_errors, onerror)
File "C:\Python26\lib\shutil.py", line 216, in rmtree
rmtree(fullname, ignore_errors, onerror)
File "C:\Python26\lib\shutil.py", line 216, in rmtree
rmtree(fullname, ignore_errors, onerror)
File "C:\Python26\lib\shutil.py", line 216, in rmtree
rmtree(fullname, ignore_errors, onerror)
File "C:\Python26\lib\shutil.py", line 216, in rmtree
rmtree(fullname, ignore_errors, onerror)
File "C:\Python26\lib\shutil.py", line 221, in rmtree
onerror(os.remove, fullname, sys.exc_info())
File "C:\Python26\lib\shutil.py", line 219, in rmtree
os.remove(fullname)
WindowsError: [Error 5] Access is denied: 'build\\tcl\\tcl8.5\\msgs\\af.msg'


Looking in File Properties dialog I noticed that
af.msg
file is set to be read-only.

So the question is: what is the simplest workaround/fix to get around this problem - given that my intention is to do an equivalent of
rm -rf build/
but on Windows? (without having to use third-party tools like unxutils or cygwin - as this code is targeted to be run on a bare Windows install with Python 2.6 w/ PyWin32 installed)

Answer

Check this question out:

http://stackoverflow.com/questions/1213706/what-user-do-python-scripts-run-as-in-windows

Apparently the answer is to change the file/folder to not be read-only and then remove it.

Here's onerror() handler from pathutils.py mentioned by @Sridhar Ratnakumar in comments:

def onerror(func, path, exc_info):
    """
    Error handler for ``shutil.rmtree``.

    If the error is due to an access error (read only file)
    it attempts to add write permission and then retries.

    If the error is for another reason it re-raises the error.

    Usage : ``shutil.rmtree(path, onerror=onerror)``
    """
    import stat
    if not os.access(path, os.W_OK):
        # Is the error an access error ?
        os.chmod(path, stat.S_IWUSR)
        func(path)
    else:
        raise
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