class ArcPyLogHandler(filename, mode='a', maxBytes=0, backupCount=0, encoding=None, delay=False, errors=None)[source]#

Bases: RotatingFileHandler

Open the specified file and use it as the stream for logging.

By default, the file grows indefinitely. You can specify particular values of maxBytes and backupCount to allow the file to rollover at a predetermined size.

Rollover occurs whenever the current log file is nearly maxBytes in length. If backupCount is >= 1, the system will successively create new files with the same pathname as the base file, but with extensions “.1”, “.2” etc. appended to it. For example, with a backupCount of 5 and a base file name of “app.log”, you would get “app.log”, “app.log.1”, “app.log.2”, … through to “app.log.5”. The file being written to is always “app.log” - when it gets filled up, it is closed and renamed to “app.log.1”, and if files “app.log.1”, “app.log.2” etc. exist, then they are renamed to “app.log.2”, “app.log.3” etc. respectively.

If maxBytes is zero, rollover never occurs.


Acquire the I/O thread lock.


Add the specified filter to this handler.


Closes the stream.


Acquire a thread lock for serializing access to the underlying I/O.


Do a rollover, as described in __init__().


Write the log message


Determine if a record is loggable by consulting all the filters.

The default is to allow the record to be logged; any filter can veto this and the record is then dropped. Returns a zero value if a record is to be dropped, else non-zero.

Changed in version 3.2: Allow filters to be just callables.


Flushes the stream.


Format the specified record.

If a formatter is set, use it. Otherwise, use the default formatter for the module.


Conditionally emit the specified logging record.

Emission depends on filters which may have been added to the handler. Wrap the actual emission of the record with acquisition/release of the I/O thread lock. Returns whether the filter passed the record for emission.


Handle errors which occur during an emit() call.

This method should be called from handlers when an exception is encountered during an emit() call. If raiseExceptions is false, exceptions get silently ignored. This is what is mostly wanted for a logging system - most users will not care about errors in the logging system, they are more interested in application errors. You could, however, replace this with a custom handler if you wish. The record which was being processed is passed in to this method.


Release the I/O thread lock.


Remove the specified filter from this handler.

rotate(source, dest)#

When rotating, rotate the current log.

The default implementation calls the ‘rotator’ attribute of the handler, if it’s callable, passing the source and dest arguments to it. If the attribute isn’t callable (the default is None), the source is simply renamed to the destination.

  • source – The source filename. This is normally the base filename, e.g. ‘test.log’

  • dest – The destination filename. This is normally what the source is rotated to, e.g. ‘test.log.1’.


Modify the filename of a log file when rotating.

This is provided so that a custom filename can be provided.

The default implementation calls the ‘namer’ attribute of the handler, if it’s callable, passing the default name to it. If the attribute isn’t callable (the default is None), the name is returned unchanged.


default_name – The default name for the log file.


Set the formatter for this handler.


Set the logging level of this handler. level must be an int or a str.


Sets the StreamHandler’s stream to the specified value, if it is different.

Returns the old stream, if the stream was changed, or None if it wasn’t.


Determine if rollover should occur.

Basically, see if the supplied record would cause the file to exceed the size limit we have.