Zanurkuj w Pythonie/Klasa opakowująca UserDict: Różnice pomiędzy wersjami

== Zgłębianie klasy <tt>UserDict</tt> <!--A Wrapper Class --> ==

 

 

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# Klasa <tt>UserDict</tt> jest klasą bazową, nie dziedziczy nic z innych klas.

# Python supports data attributes (called “instance variables” in Java and Powerbuilder, and “member variables” in C++). Data attributes are pieces of data held by a specific instance of a class. In this case, each instance of UserDict will have a data attribute data. To reference this attribute from code outside the class, you qualify it with the instance name, instance.data, in the same way that you qualify a function with its module name. To reference a data attribute from within the class, you use self as the qualifier. By convention, all data attributes are initialized to reasonable values in the __init__ method. However, this is not required, since data attributes, like local variables, spring into existence when they are first assigned a value.

# The update method is a dictionary duplicator: it copies all the keys and values from one dictionary to another. This does not clear the target dictionary first; if the target dictionary already has some keys, the ones from the source dictionary will be overwritten, but others will be left untouched. Think of update as a merge function, not a copy function.