Fileconveyor错误-UnboundLocalError：分配前已引用局部变量'classname'

Question

I am using fileconvayor form https://github.com/wimleers/fileconveyor

but when I run the script I get the following error.

Traceback (most recent call last):
File "arbitrator.py", line 1185, in <module>
run_file_conveyor()
File "arbitrator.py", line 1168, in run_file_conveyor
arbitrator = Arbitrator(os.path.join(FILE_CONVEYOR_PATH, "config.xml"), rest
art)
File "arbitrator.py", line 142, in __init__
transporter_class = self._import_transporter(transporter_name)
File "arbitrator.py", line 1162, in _import_transporter
self.logger.error("The Transporter module '%s' was found, but its Transporte
r class '%s' could not be found."  % (module_name, classname))
UnboundLocalError: local variable 'classname' referenced before assignment
[root@af-server fileconveyor]#

Here is the code from arbitrator.py line 142

   # Verify that all referenced transporters are available.
    transporters_not_found = 0
    for server in self.config.servers.keys():
        transporter_name = self.config.servers[server]["transporter"]
        transporter_class = self._import_transporter(transporter_name)
        if not transporter_class:
            transporters_not_found += 1
    if transporters_not_found > 0:
        raise TransporterAvailabilityTestError("Consult the log file for details")

and the code from line 1162

transporter_class = None
    module = None
    alternatives = [transporter]
    default_prefix = 'transporters.transporter_' # Not  'fileconveyor.transporters.transporter_'!
    if not transporter.startswith(default_prefix):
        alternatives.append('%s%s' % (default_prefix, transporter))
    for module_name in alternatives:
        try:
            module = __import__(module_name, globals(), locals(), ["TRANSPORTER_CLASS"], -1)
        except ImportError:
            pass
    if not module:
        msg = "The transporter module '%s' could not be found." % transporter
        if len(alternatives) > 1:
            msg = '%s Tried (%s)' % (msg, ', '.join(alternatives))
        self.logger.error(msg)
    else:
        try:
            classname = module.TRANSPORTER_CLASS
            module = __import__(module_name, globals(), locals(), [classname])
            transporter_class = getattr(module, classname)
        except AttributeError:
            self.logger.error("The Transporter module '%s' was found, but its Transporter class '%s' could not be found."  % (module_name, classname))
    return transporter_class

Here is whole code form that file

http://pastebin.com/ctsLrckq

Answer 1

I got the same error when I installed fileconveyor followed the guide INSTALL.txt. It looks like there are some unresolved dependencies. Try solve it with:

pip install django-cumulus==1.0.10

Answer 2

The exception is catching an error two lines earlier than you thought: it is coming in the classname = module.TRANSPORTER_CLASS . Whatever module is, it doesn't have a TRANSPORTER_CLASS attribute, so an exception is raised and classname` is never defined. If you weren't swallowing the actual error message, that would be clear.

I must say though that this code makes very little sense. In that else clause you already have module , so why are you reimporting it on the following line?

Answer 3

This line:

classname = module.TRANSPORTER_CLASS

throws an AttributeError exception, because module doesn't have a TRANSPORTER_CLASS attribute. This causes the interpreter to jump to the self.logger.error(...) line before the classname variable is defined. Formatting the log string fails when the logger line tries to use the undefined variable. In order to fix it, you could replace the logger line with this one:

self.logger.error("The Transporter module '%s' was found, but its Transporter class could not be found."  % (module_name,))

Please note that __import__ can raise ImportError , which is not catched. I guess the author of this code meant to catch it.