Why would shutil.copy() raise a permission exception when cp doesn't?

shutil.copy() is raising a permissions error:

Traceback (most recent call last):
  File "copy-test.py", line 3, in <module>
    shutil.copy('src/images/ajax-loader-000000-e3e3e3.gif', 'bin/styles/blacktie/images')
  File "/usr/lib/python2.7/shutil.py", line 118, in copy
    copymode(src, dst)
  File "/usr/lib/python2.7/shutil.py", line 91, in copymode
    os.chmod(dst, mode)
OSError: [Errno 1] Operation not permitted: 'bin/styles/blacktie/images/ajax-loader-000000-e3e3e3.gif'

copy-test.py:

import shutil

shutil.copy('src/images/ajax-loader-000000-e3e3e3.gif', 'bin/styles/blacktie/images')

I am running copy-test.py from the command line:

python copy-test.py

But running cp from the command line on the same file to the same destination doesn't cause an error. Why?

Solution

The operation that is failing is chmod, not the copy itself:

  File "/usr/lib/python2.7/shutil.py", line 91, in copymode
    os.chmod(dst, mode)
OSError: [Errno 1] Operation not permitted: 'bin/styles/blacktie/images/ajax-loader-000000-e3e3e3.gif'

This indicates that the file already exists and is owned by another user.

shutil.copy is specified to copy permission bits. If you only want the file contents to be copied, use shutil.copyfile(src, dst), or shutil.copyfile(src, os.path.join(dst, os.path.basename(src))) if dst is a directory.

A function that works with dst either a file or a directory and does not copy permission bits:

def copy(src, dst):
    if os.path.isdir(dst):
        dst = os.path.join(dst, os.path.basename(src))
    shutil.copyfile(src, dst)