In my previous post I looked at some of the basics of Python. In this post I want to dig further into the syntax etc. for classes within Python.<\/p>\n
Class naming conventions<\/strong><\/p>\n We prefix a class name with the class<\/em> keyword. Python naming convention<\/a> suggests the class name should be Pascal case, i.e. ClassName.<\/p>\n The method naming convention<\/a>, by default, should be all lowercase with underscores (snake case) to separate words, i.e. method_name. <\/p>\n Private\/protected methods and instance variables should have an underscore prefix, i.e. _private_name.<\/p>\n Defining a class<\/strong><\/p>\n The special method name __init__<\/em> can be thought of a little like a constructor, however we cannot overload it, but we can pass arguments into it<\/p>\n Note: Whilst it might appear possible to have multiple __init__ methods, it’s the last one declared which seems to be the one available to calling code.<\/em><\/p>\n We terminate the line that the class<\/em> keyword is on with the colon and then methods or variables start on a new line and indented with a tab.<\/p>\n The self<\/em> parameter passed to __init__ or any other class method is passed implicitly, i.e. we do not supply the self, Python does that for us.<\/p>\n Inheritance<\/strong><\/p>\n Python classes support inheritance (even multiple inheritance) by declaring the base classes in a comma separated list within parenthesis, i.e.<\/p>\n In this example you can see how we can call the base class’ __init__<\/em> method. The Dog class derives from both Animal and Mammal classes (in this instance the Mammal class has no methods etc. hence uses pass<\/em> statement to create the empty class).<\/p>\n Calling base methods in Multiple Inheritance<\/strong><\/p>\n Multiple inheritance always has the issue around what base method to call in situations where there’s multiple methods of the same name, for example if we have the following<\/p>\n then what base class method is actually called via c.name()<\/em>.<\/p>\n A quick note: In the above as we’re missing the method name() on the class C, this can be seen as the following <\/p>\n\r\nclass Animal:\r\n def __init__(self, name):\r\n self.name = name\r\n<\/pre>\n
\r\nclass Animal:\r\n def __init__(self, name):\r\n self.name = name\r\n\r\n\r\nclass Mammal:\r\n pass\r\n\r\n\r\nclass Dog(Animal, Mammal):\r\n def __init__(self):\r\n super().__init__("Dog")\r\n<\/pre>\n\r\nclass A:\r\n def name(self):\r\n print("A")\r\n\r\nclass B:\r\n def name(self):\r\n print("B")\r\n\r\n\r\nclass C(A, B):\r\n pass\r\n\r\nc = C()\r\nc.name()\r\n<\/pre>\n\r\nclass C(A, B):\r\n def name(self):\r\n super(C, self).name()\r\n<\/pre>\n