Object Orientation in Python - Classes in Python (Page 3 of 4 )
Now that you have an understanding of what object orientation is, we'll move on to Python. The first logical step is to create a class. You can define a class pretty much anywhere, including inside conditional statements. Defining a class is simple:
class SomeClass:
The next step is to add a bit of data to the class. There isn't anything special or unique about this step:
class SomeClass:
"Just some class...that's all."
someNumber = 127 + 1 / 360 * 2 + 1 / 2
someString = 'Star Office 7'
You can also add methods. These are defined just like functions, except they take self as their first argument:
class SomeClass
"Just some class...that's all."
someNumber – 127 + 1 / 360 * 2 + 1 / 2
someString = 'Star Office 7'
def someFunction ( self ):
return someString + ' tastes like chicken.'
def someOtherFunction ( self ):
return False
As you can see, it's pretty simple to create a class with data and methods.
Next, we must create an instance of our class, or an object derived from it. This is extremely simple and brief:
someObject = SomeClass()
We can now access the variables defined in our class:
someObject.someNumber
someObject.someString
Calling the methods defined in our class is also very simple:
someObject.someFunction()
someObject.someOtherFunction()
It is also possible to define attributes after we have created the object:
someObject.someRandomVariable = 5
Similarly, it is possible to clean up what we create:
del someObject.someRandomVariable
Let's say we want to define a variable when we first create an instance of our class. This can be accomplished by creating a special method of our class, __init__. The method will be executed when our class is first created.
class AnotherClass:
def __init__ ( self, anotherArgument ):
self.anotherArgument = anotherArgument
anotherObject = AnotherClass ( 'Hello object-oriented world.' )
print anotherObject.anotherArgument # "Hello object-oriented world."
Next: More About Creating Classes >>
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