ebb-lint 0.4.0

lint for ensuring quality software

ebb-lint

It’s a flake8 plugin! It lints for style problems! To activate it:

$ pip install ebb-lint

Configuration

Configuration does nothing but cause bugs or laxness, so ebb-lint recommends keeping the defaults as-is. However, there are two configuration options provided for dealing with long lines. Both can be specified either on the command line by passing flags to flake8, or with the typical configuration methods.

hard-max-line-length

Lines must never be longer than this value. The default is 119 columns.

permissive-bulkiness-percentage

Lines can exceed max-line-length (which is considered the “soft limit”) only if the line contains greater than or equal to this percentage of string literals or comments, but the percentages of each are not combined. The default is 67%. For more detail, see the section about long lines.

When writing a one-off script, to use print against ebb-lint‘s wishes, add a comment to the top of the file to disable that warning:

# I sincerely swear that this is one-off code.

This comment must be above any statements in the code (including docstrings), on a line by itself.

noqa

ebb-lint disables # noqa comments with extreme prejudice. The feature is over-used and over-general; it’s not possible to only mark certain errors as acceptable, and as a result, it’s possible for a line marked noqa for one error to completely mask a different error.

Errors

All of the possible errors, organized by category:

L1: Docstrings

L101

The __init__ method of classes must not have a docstring, as it is standard sphinx style to put that information on the class docstring.

L102

A docstring was incorrectly formatted. Single-line docstrings must resemble this:

def func():
    """Spam eggs."""

Multi-line docstrings must resemble this:

def func():
    """
    Spam eggs.

    Also, sausage.
    """

L103

A test docstring (i.e. the docstring on a function or method with a name starting with test_) must not start with any form of the words “test”, “verify”, or “ensure”.

L104

Docstrings must use Napoleon, not reStructuredText fields.

L2: Dubious syntax

Some features of python do more harm than good. These errors catch potential problems in situations where the programmer might have intended to do one thing, but accidentally did something else instead.

L201

Container literals must have a trailing comma following the last element. If the closing ), ], or } is on the same line as the last element, this error is not emitted.

L202

print is not allowed except for debugging. For production code, logging is much more flexible and predictable. This can be disabled in one-off scripts.

L203

pdb and compatible modules (i.e. modules exposing a set_trace function) are not allowed except for debugging. If a set_trace call was allowed into production, it would likely wedge the process.

L204

Implicit string literal concatenation (i.e. 'spam' 'eggs' being isomorphic to 'spameggs') is only allowed if every string being concatenated is parenthesized, and the parentheses contain nothing but string literals.

This is okay:

some_string = ('spam {} '
               'eggs').format('spam')

And this is not:

some_list = [
    'spam'
    'eggs',
    'sausage',
]

L205

__init__.py is not allowed to contain function or class definitions.

L206

Implicit relative imports are not allowed.

L207

pass is only necessary in non-optional suites containing no other statements. If a suite contains another statement, adding pass is redundant. Docstrings count as a statement.

Non-optional suites are the suites of, for example, def, class, and if. else and finally suites are optional, and as such this is never necessary:

if predicate():
    do_something()
else:
    pass

try:
    do_something()
finally:
    pass

L208

Pokémon exception handling is always a mistake. If the intent is really to catch and ignore exceptions, explicitly name which exception types to silence.

L209

return, del, raise, assert, print (in python 2, without print_function) yield, and yield from are statements, not functions, and as such, do not require parentheses.

This is okay:

return (
  a
  + b)

And this is not:

return(a + b)

L210

Instead of intentionally relying on the side effects of map, filter, or a comprehension, write an explicit for loop.

This is okay:

for x in y:
    print(x)

And this is not:

map(print, y)

L211

Using map or filter with a lambda as the first argument is always better written as list comprehension or generator expression. An expression is more readable and extensible, and less importantly, doesn’t incur as much function call overhead.

L212

Using @staticmethod is always wrong. The two most common situations are:

• Wanting to do something with the class but without an instance, in which case @classmethod is the correct solution.

• Wanting to ‘namespace’ a function on a class, but this isn’t Java, so make it a module-scoped function instead.

Using staticmethod on its own is not a problem; this is perfectly acceptable for testing purposes:

from some_module import do_some_more_io, some_io


def do_io():
    return some_io()


class Spam(object):
    do_io = staticmethod(do_io)
    do_some_more_io = staticmethod(do_some_more_io)

L3: Formatting

L301

Files must end with a trailing newline.

L302

The line was too long.

Lines greater than hard-max-line-length (which is considered the “hard limit”, and by default is 119 columns) are never allowed. Lines greater than max-line-length (which is considered the “soft limit”, and by default is 79 columns) are allowed if and only if the line contains above a certain percentage of string literals or comments. The percentages of both are not combined. The “certain percentage” allowed is permissive-bulkiness-percentage, which by default is 67%.

For all of the following examples, the soft limit is 15 columns, and the hard limit is 25 columns.

Disallowed because, at 20 characters, the line exceeds the soft limit, and the whole line is only 15% string literals by character count:

ultradignified = 'y'

Allowed because the whole line is 80% string literals by character count:

t = 'electroplating'

Allowed because the whole line is 75% comments by character count:

f()  # accreditation

Disallowed because the whole line is 20% comments and 50% string literals by character count, and neither of those is at or above 67%:

d = 'smallpox'  # ok

Disallowed because the whole line is 26 characters long, which exceeds the hard limit:

thyroparathyroidectomize()

The hard-max-line-length and permissive-bulkiness-percentage can be configured; see the section Configuration.

L303

noqa is ignored, and as such, # noqa comments should be deleted to reduce pointless noise.