How to create task?

If you want to create task you need to implement derived class from longtask.Task. You also need to override few things:

• name - task name,

• get_items() - this method should return you items collection,

• process_item(item) - in this method you can process your item.

Simple example - resize many pictures (resize.py):

import longtask
import glob
from PIL import Image


class ResizeTask(longtask.Task):
    name = 'resize'

    def get_items(self):
        return glob.glob('*.png')

    def process_item(self, item):
        original_image = Image.open(item)
        resized_image = original_image.resize((100, 100))
        resized_image.save('output/' + item)


if __name__ == '__main__':
    ResizeTask().run()

Now in directory with *.png images you can run:

$ python resize.py
[*] Starting task: resize [2013-03-03 18:36:29.953306]
[*] Processed: 100% (1000/1000) errors: 10% (100/1000) |###################| Elapsed Time: 1:00:00 ETA:  0:00:00
[*] Finished task: resize [2013-03-03 18:36:30.080421]
[*] Stats:
  - processed: 100% (1000/1000)
  - success: 90% (900/1000)
  - errors: 10% (100/1000)
    - 100 x IOError with traceback:

Traceback (most recent call last):
  File "/Users/konradhalas/dev/workspace/personal/longtask/longtask/task.py", line 59, in run
    self.process_item(item)
  File "resize.py", line 13, in process_item
    original_image = Image.open(item)
  File "/Users/konradhalas/dev/virtualenvs/longtask/lib/python2.7/site-packages/PIL/Image.py", line 1980, in open
    raise IOError("cannot identify image file")
IOError: cannot identify image file

In our example we resized 1000 files - 100 of them have corrupted data (IOError). This task took 1h.

You can always stop task with Ctrl+C and rerun it later with flag -c. If some errors occured durring execution you can rerun it with flag -e (it works only with flag -c).

License

Copyright [2013] [Konrad Hałas]

Licensed under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.