rspec/rules/S2710/python/rule.adoc

== Why is this an issue?

By convention, the first argument to class methods, i.e. methods decorated with ``++@classmethod++``, is named ``++cls++`` as a representation and a reminder that the argument is the class itself. Name the argument something else, and you stand a good chance of confusing both users and maintainers of the code. It might also indicate that the ``++cls++`` parameter was forgotten, in which case calling the method will most probably fail. This rule also applies to methods ``++__init_subclass__++``, ``++__class_getitem__++`` and ``++__new__++`` as their first argument is always the class instead of "self".


By default this rule accepts ``++cls++`` and ``++mcs++``, which is sometime used in metaclasses, as valid names for class parameters. You can set your own list of accepted names via the parameter ``++classParameterNames++``.


This rule raises an issue when the first parameter of a class method is not an accepted name.


=== Noncompliant code example

[source,python]
----
class Rectangle(object):

  @classmethod
  def area(bob, height, width):  #Noncompliant
    return height * width
----


=== Compliant solution

[source,python]
----
class Rectangle(object):

  @classmethod
  def area(cls, height, width):
    return height * width
----


== Resources

* PEP8 - https://www.python.org/dev/peps/pep-0008/#function-and-method-arguments[Function and Method Arguments]



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== Comments And Links
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