flake8-holvi is a flake8 plugin that helps writing Python 3-compatible and more Pythonic code in Holvi projects.

It's not uploaded to our PyPI server yet. The simplest way to install it is from GitHub with pip:

$ pip install -e git+https://github.com/holvi/flake8-holvi.git#egg=flake8-holvi

You don't need to do anything else to be able to use it. However, you can use the --select option if you only want to see violations found by flake8-holvi:

$ flake8 --select=HLV bankgw/

Or in setup.cfg, you can use the enable-extensions setting:

[flake8] enable-extensions=HLV

Reporting warnings can be disabled by passing the --disable-warnings option.

Currently, flake8-holvi detects the following cases as errors and warnings respectively:

1. unicode(...)  # Should be replaced with six.text_type().

2. # Should have encoding parameter.
   unicode('text with non-ASCII characters: ıçğüş')

   Correct usage:

   unicode('text with non-ASCII characters: ıçğüş', 'utf-8')

3. # Should be used a non-ASCII encoding.
   unicode('text with non-ASCII characters: ıçğüş', 'ascii')

   Correct usage:

   unicode('text with non-ASCII characters: ıçğüş', 'utf-8')

4. Incorrect usage:

   logger.debug('Some debug information: %s' % foo)

   Correct usage:

   logger.debug('Some debug information: %s', foo)

5. Incorrect usage:

   logger.debug('Some debug information: {}'.format(foo))

   Correct usage:

   logger.debug('Some debug information: %s', foo)

6. str(...)  # Should be replaced with six.binary_type().

7. Incorrect usage (1):

   for event in events:
       transaction.on_commit(lambda: task.apply_async((event.id,)))

   Correct usage (1):

   for event in events:
       transaction.on_commit(lambda event=event: task.apply_async((event.id,)))

   Incorrect usage (2):

   for event in events:
       transaction.on_commit(lambda user=user: task.apply_async((event.id, user.email)))

   Correct usage (2):

   for event in events:
       transaction.on_commit(lambda event=event, user=user: task.apply_async((event.id, user.email)))

8. Suggests six.moves imports when it finds Python 2-only imports.

9. Suggests six.<assertion_name> aliases when it finds Python 2-only unittest assertions.

10. Detects potential implicit relative imports that can be seen in a typical Django project.

1. Potentially dangerous usage:

   ascii_only_content = get_data_from_external_api()
   unicode(ascii_only_content)

   Safer usage since the default string encoding is 'ascii' in Python 2 and get_data_from_external_api() can return non-ASCII data:

   unicode(ascii_only_content, 'utf-8')

2. Potentially dangerous usage:

   ascii_only_content = get_data_from_external_api()
   unicode(ascii_only_content, 'ascii')

   'ascii' should be passed only if we are 100% sure ascii_only_content will always be ASCII-only:

   >>> non_ascii_content = "ıçğü"
   >>> unicode(non_ascii_content)
   Traceback (most recent call last):
     File "<stdin>", line 1, in <module>
   UnicodeDecodeError: 'ascii' codec can't decode byte 0xc4 in position 0: ordinal not in range(128)

   Otherwise use a more appropriate encoding:

   unicode(ascii_only_content, better_encoding)