How to catch exceptions of copytree in python

Question

The documentation of shutil.copytree states:

If exception(s) occur, an Error is raised with a list of reasons.

And the link refers to:

exception shutil.Error This exception collects exceptions that are raised during a multi-file operation. For copytree(), the exception argument is a list of 3-tuples (srcname, dstname, exception).

What is this shutil.Error exception? I tried to catch this type of exception:

try:
  shutil.copytree(source, dest) # this throws a FileExistsError for example
except shutil.Error:
    # error handling

But this kind of error wasn't raised..

Answer 1

The documentation first states

dirs_exist_ok dictates whether to raise an exception in case dst or any missing parent directory already exists.

Unless you specify dirs_exist_ok=True a FileExistsError is raised. You're right that later on the documentation states that (presumably in other cases) a shutil.Error may be raised.

In the end I think it's a matter of interpretation, but if the code raises a FileExistsError you should catch a FileExistsError :

try:
  shutil.copytree(source, dest)
except FileExistsError:
    # error handling

>>> shutil.copytree("ws", "workshop")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/robin/.pyenv/versions/3.8.6/lib/python3.8/shutil.py", line 554, in copytree
    return _copytree(entries=entries, src=src, dst=dst, symlinks=symlinks,
  File "/home/robin/.pyenv/versions/3.8.6/lib/python3.8/shutil.py", line 455, in _copytree
    os.makedirs(dst, exist_ok=dirs_exist_ok)
  File "/home/robin/.pyenv/versions/3.8.6/lib/python3.8/os.py", line 223, in makedirs
    mkdir(name, mode)
FileExistsError: [Errno 17] File exists: 'workshop'
>>> shutil.copytree("ws", "workshop", dirs_exist_ok=True)
'workshop'

The part of shutil.Error that you quoted could be interpreted as:

This exception collects exceptions that are raised during a multi-file operation. For copytree(), [ when a shutil.Error is raised ] the exception argument is a list of 3-tuples (srcname, dstname, exception).

It does not mean that all exceptions during copytree() will be of type shutil.Error .