David Aldrich wrote:
> Hi
>
> I have a function that compares a set of files with a reference set of
> files. All files are compared and then, if any differences were found, an
> exception is raised:
>
> class Error(Exception): pass
>
> def check_results(file_list):
>
> <snip>
>
> if isDifferent:
> raise Error('One or more result files differ from the reference
> result files')
>
> I would like to pass back to the caller a list of the files that failed.
> How would I include that list in the exception object?
While you can pass them as just another argument
>>> class UnexpectedFileContents(Exception):
... pass
...
>>> try:
... raise UnexpectedFileContents("Some files differ from the reference",
["foo.txt", "bar.py", "baz.rst"])
... except UnexpectedFileContents as err:
... print(err)
... print("The problematic files are")
... print("\n".join(err.args[1]))
...
('Some files differ from the reference', ['foo.txt', 'bar.py', 'baz.rst'])
The problematic files are
foo.txt
bar.py
baz.rst
it's probably a good idea to put in a bit more work:
>>> class UnexpectedFileContents(Exception):
... def __init__(self, message, files):
... super().__init__(message)
... self.files = files
...
>>> try:
... raise UnexpectedFileContents("Some files differ from the reference",
["foo.txt", "bar.py", "baz.rst"])
... except UnexpectedFileContents as err:
... print(err)
... print("The problematic files are")
... print("\n".join(err.files))
...
Some files differ from the reference
The problematic files are
foo.txt
bar.py
baz.rst
If you like you can add defaults and adapt the __str__() method:
>>> class UnexpectedFileContents(Exception):
... def __init__(self, message="Some files differ from the reference",
files=None):
... self.message = message
... self.files = files
... def __str__(self):
... s = self.message
... if self.files is not None:
... s = s + ": " + ", ".join(self.files)
... return s
...
>>> try: raise UnexpectedFileContents(files=["foo.txt", "bar.py",
"baz.rst"])
... except UnexpectedFileContents as err: print(err)
...
Some files differ from the reference: foo.txt, bar.py, baz.rst
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