Naming¶
Naming is hard! It is, in fact, one of the two hardest problems.
These checks are required to make your application easier to read and understand by multiple people over the long period of time.
Naming convention¶
Our naming convention tries to cover all possible cases. It is partially automated with this linter, but:
Some rules are still WIP
Some rules will never be automated, code reviews to the rescue!
General¶
Use only
ASCII
chars for namesDo not use transliteration from any other languages, translate names instead
Use clear names, do not use words that do not mean anything like
obj
Use names of an appropriate length: not too short, not too long
Protected members should use underscore as the first char
Private names with two leading underscores are not allowed
If you need to explicitly state that the variable is unused, prefix it with
_
or just use_
as a nameDo not use variables that are stated to be unused, rename them when actually using them
Whenever you want to name your variable similar to a keyword or builtin, use trailing
_
Do not use consecutive underscores
When writing abbreviations in
UpperCase
capitalize all letters:HTTPAddress
When writing abbreviations in
snake_case
use lowercase:http_address
When writing numbers in
snake_case
do not use extra_
before numbers as inhttp2_protocol
Packages¶
Packages must use
snake_case
One word for a package is the most preferable name
Modules¶
Modules must use
snake_case
Module names must not overuse magic names
Module names must be valid Python identifiers
Classes¶
Classes must use
UpperCase
Python’s built-in classes, however, are typically lowercase words
Exception classes must end with
Error
Instance attributes¶
Instance attributes must use
snake_case
with no exceptions
Class attributes¶
Class attributes must use
snake_case
with no exceptions
Functions and methods¶
Functions and methods must use
snake_case
with no exceptions
Method and function arguments¶
Instance methods must have their first argument named
self
Class methods must have their first argument named
cls
Metaclass methods must have their first argument named
mcs
Python’s
*args
and**kwargs
should be default names when just passing these values to some other method/function, unless you want to use these values in place, then name them explicitlyKeyword-only arguments must be separated from other arguments with
*
Global (module level) variables¶
Global variables must use
CONSTANT_CASE
Unless other is required by the API, example:
urlpatterns
in Django
Variables¶
Variables must use
snake_case
with no exceptionsWhen a variable is unused it must be prefixed with an underscore:
_user
Type aliases¶
Must use
UpperCase
as real classesMust not contain word
type
in its nameGeneric types should be called
TT
orKT
orVT
Covariant and contravariant types should be marked with
Cov
andContra
suffixes, in this case, one letter can be dropped:TCov
andKContra
Summary¶
Forbids to use blacklisted module names. |
|
Forbids to use any magic names except whitelisted ones. |
|
Forbids to use module names that do not match our pattern. |
|
Forbids to have blacklisted variable names. |
|
Forbids to have too short variable or module names. |
|
Forbids to have private name pattern. |
|
Forbids to use the same alias as the original name in imports. |
|
Forbids to have names with underscored numbers pattern. |
|
Forbids to use anything but |
|
Forbids to use more than one consecutive underscore in variable names. |
|
Forbids to name your variables as |
|
Forbids to have long short variable or module names. |
|
Forbids to use unicode names. |
|
Forbids to use trailing |
|
Forbids to have use variables that are marked as unused. |
Module names¶
-
class
WrongModuleNameViolation
(node=None, text=None)[source]¶ Bases:
wemake_python_styleguide.violations.base.SimpleViolation
Forbids to use blacklisted module names.
- Reasoning:
Some module names are not expressive enough. It is hard to tell what you can find inside the
utils.py
module.- Solution:
Rename your module, reorganize the contents.
See
MODULE_NAMES_BLACKLIST
for the full list of bad module names.Example:
# Correct: github.py views.py # Wrong: utils.py helpers.py
New in version 0.1.0.
-
error_template
= 'Found wrong module name'¶
-
code
= 100¶
-
class
WrongModuleMagicNameViolation
(node=None, text=None)[source]¶ Bases:
wemake_python_styleguide.violations.base.SimpleViolation
Forbids to use any magic names except whitelisted ones.
- Reasoning:
Do not fall in love with magic. There’s no good reason to use magic names when you can use regular names.
See
MAGIC_MODULE_NAMES_WHITELIST
for the full list of allowed magic module names.Example:
# Correct: __init__.py __main__.py # Wrong: __version__.py
New in version 0.1.0.
-
error_template
= 'Found wrong module magic name'¶
-
code
= 101¶
-
class
WrongModuleNamePatternViolation
(node=None, text=None)[source]¶ Bases:
wemake_python_styleguide.violations.base.SimpleViolation
Forbids to use module names that do not match our pattern.
- Reasoning:
Module names must be valid python identifiers. And just like the variable names - module names should be consistent. Ideally, they should follow the same rules. For
python
world it is common to usesnake_case
notation.
We use
MODULE_NAME_PATTERN
to validate the module names.Example:
# Correct: __init__.py some_module_name.py test12.py # Wrong: _some.py MyModule.py 0001_migration.py
New in version 0.1.0.
-
error_template
= 'Found incorrect module name pattern'¶
-
code
= 102¶
General names¶
-
class
WrongVariableNameViolation
(node, text=None)[source]¶ Bases:
wemake_python_styleguide.violations.base.ASTViolation
Forbids to have blacklisted variable names.
- Reasoning:
We have found some names that are not expressive enough. However, they appear in the code more than often. All names that we forbid to use could be improved.
- Solution:
Try to use a more specific name instead. If you really want to use any of the names from the list, add a prefix or suffix to it. It will serve you well.
See
VARIABLE_NAMES_BLACKLIST
for the full list of blacklisted variable names.Example:
# Correct: html_node_item = None # Wrong: item = None
New in version 0.1.0.
-
error_template
= 'Found wrong variable name: {0}'¶
-
code
= 110¶
-
class
TooShortNameViolation
(node=None, text=None)[source]¶ Bases:
wemake_python_styleguide.violations.base.MaybeASTViolation
Forbids to have too short variable or module names.
- Reasoning:
It is hard to understand what the variable means and why it is used, if its name is too short.
- Solution:
Think of another name. Give more context to it.
This rule checks: modules, variables, attributes, functions, methods, and classes.
Example:
# Correct: x_coordinate = 1 abscissa = 2 # Wrong: x = 1 y = 2
- Configuration:
This rule is configurable with
--min-name-length
. Default: 2
New in version 0.1.0.
Changed in version 0.4.0.
-
error_template
= 'Found too short name: {0}'¶
-
code
= 111¶
-
class
PrivateNameViolation
(node=None, text=None)[source]¶ Bases:
wemake_python_styleguide.violations.base.MaybeASTViolation
Forbids to have private name pattern.
- Reasoning:
Private is not private in
python
. So, why should we pretend it is? This might lead to some serious design flaws.- Solution:
Rename your variable or method to be protected. Think about your design, why do you want to make it private? Are there any other ways to achieve what you want?
This rule checks: modules, variables, attributes, functions, and methods.
Example:
# Correct: def _collect_coverage(self): ... # Wrong: def __collect_coverage(self): ...
New in version 0.1.0.
Changed in version 0.4.0.
-
error_template
= 'Found private name pattern: {0}'¶
-
code
= 112¶
-
class
SameAliasImportViolation
(node, text=None)[source]¶ Bases:
wemake_python_styleguide.violations.base.ASTViolation
Forbids to use the same alias as the original name in imports.
- Reasoning:
Why would you even do this in the first place?
Example:
# Correct: from os import path # Wrong: from os import path as path
New in version 0.1.0.
-
error_template
= 'Found same alias import: {0}'¶
-
code
= 113¶
-
class
UnderscoredNumberNameViolation
(node=None, text=None)[source]¶ Bases:
wemake_python_styleguide.violations.base.MaybeASTViolation
Forbids to have names with underscored numbers pattern.
- Reasoning:
This is done for consistency in naming.
- Solution:
Do not put an underscore between text and numbers, that is confusing. Rename your variable or modules do not include underscored numbers.
This rule checks: modules, variables, attributes, functions, method, and classes. Please, note that putting an underscore that replaces
-
in some names between numbers are fine, example:ISO-123-456
would becomeiso123_456
.Example:
# Correct: star_wars_episode2 = 'awesome!' iso123_456 = 'some data' # Wrong: star_wars_episode_2 = 'not so awesome' iso_123_456 = 'some data'
New in version 0.3.0.
Changed in version 0.4.0.
-
error_template
= 'Found underscored name pattern: {0}'¶
-
code
= 114¶
-
class
UpperCaseAttributeViolation
(node, text=None)[source]¶ Bases:
wemake_python_styleguide.violations.base.ASTViolation
Forbids to use anything but
snake_case
for naming class attributes.- Reasoning:
Constants with upper-case names belong on a module level.
- Solution:
Move your constants to the module level. Rename your variables so that they conform to
snake_case
convention.
Example:
# Correct: MY_MODULE_CONSTANT = 1 class A(object): my_attribute = 42 # Wrong: class A(object): MY_CONSTANT = 42
New in version 0.3.0.
-
error_template
= 'Found upper-case constant in a class: {0}'¶
-
code
= 115¶
-
class
ConsecutiveUnderscoresInNameViolation
(node=None, text=None)[source]¶ Bases:
wemake_python_styleguide.violations.base.MaybeASTViolation
Forbids to use more than one consecutive underscore in variable names.
- Reasoning:
This is done to gain extra readability. This naming rule already exists for module names.
Example:
# Correct: some_value = 5 __magic__ = 5 # Wrong: some__value = 5
This rule checks: modules, variables, attributes, functions, and methods.
New in version 0.3.0.
Changed in version 0.4.0.
-
error_template
= 'Found consecutive underscores name: {0}'¶
-
code
= 116¶
-
class
ReservedArgumentNameViolation
(node, text=None)[source]¶ Bases:
wemake_python_styleguide.violations.base.ASTViolation
Forbids to name your variables as
self
,cls
, andmcs
.- Reasoning:
These names are special, they should only be used as first arguments inside methods.
Example:
# Correct: class Test(object): def __init__(self): ... # Wrong: cls = 5 lambda self: self + 12
This rule checks: functions and methods. Having any reserved names in
lambda
functions is not allowed.New in version 0.5.0.
-
error_template
= 'Found name reserved for first argument: {0}'¶
-
code
= 117¶
-
class
TooLongNameViolation
(node=None, text=None)[source]¶ Bases:
wemake_python_styleguide.violations.base.MaybeASTViolation
Forbids to have long short variable or module names.
- Reasoning:
Too long names are unreadable. It is better to use a shorter alternative. Long names also indicate that this variable is too complex, maybe it may require some documentation.
- Solution:
Think of another name. Give less context to it.
This rule checks: modules, variables, attributes, functions, methods, and classes.
Example:
# Correct: total_price = 25 average_age = 45 # Wrong: final_price_after_fifteen_percent_sales_tax_and_gratuity = 30 total_age_of_all_participants_in_the_survey_divided_by_twelve = 2
- Configuration:
This rule is configurable with
--max-name-length
. Default: 45
New in version 0.5.0.
-
error_template
= 'Found too long name: {0}'¶
-
code
= 118¶
-
class
UnicodeNameViolation
(node=None, text=None)[source]¶ Bases:
wemake_python_styleguide.violations.base.MaybeASTViolation
Forbids to use unicode names.
- Reasoning:
This should be forbidden for sanity, readability, and writability.
- Solution:
Rename your entities so that they contain only ASCII symbols.
This rule checks: modules, variables, attributes, functions, methods, and classes.
Example:
# Correct: some_variable = 'Text with russian: русский язык' # Wrong: переменная = 42 some_變量 = ''
New in version 0.5.0.
-
error_template
= 'Found unicode name: {0}'¶
-
code
= 119¶
-
class
TrailingUnderscoreViolation
(node, text=None)[source]¶ Bases:
wemake_python_styleguide.violations.base.ASTViolation
Forbids to use trailing
_
for names that do not need it.- Reasoning:
We use trailing underscore for a reason: to indicate that this name shadows a built-in or keyword. So, when overusing this feature for general names: it just harms readability of your program.
- Solution:
Rename your variable not to contain trailing underscores.
This rule checks: variables, attributes, functions, methods, and classes.
Example:
# Correct: class_ = SomeClass list_ = [] # Wrong: some_variable_ = 1
New in version 0.7.0.
-
error_template
= 'Found regular name with trailing underscore: {0}'¶
-
code
= 120¶
-
class
UnusedVariableIsUsedViolation
(node, text=None)[source]¶ Bases:
wemake_python_styleguide.violations.base.ASTViolation
Forbids to have use variables that are marked as unused.
- Reasoning:
Sometimes you start to use new logic in your functions, and you start to use variables that once were marked as unused. But, you have not renamed them for some reason. And now you have a lot of confusion: the variable is marked as unused, but you are using it. Why? What’s going on?
- Solution:
Rename your variable to be a regular variable without a leading underscore.
Example:
# Correct: def function(): first = 15 return first + 10 # Wrong: def function(): _first = 15 return _first + 10
This rule checks: functions, methods, and
lambda
functions.New in version 0.7.0.
-
error_template
= 'Found usage of a variable marked as unused: {0}'¶
-
code
= 121¶