Emily Fortuna wrote: > Hi friends, > I am learning Python and relating to my knowledge of Java... What is (Is > there?) the equivalent of Java interfaces in Python? How could I write > my own?
Explicit, formal interfaces are used much less frequently in Python than in Java, and for beginners they are not needed at all. In Python, interfaces are often implicit and defined only by usage and documentation. Sometimes the usage is called a protocol. Because Python is dynamic, there is not need to declare the type of an object, you just use it in the desired way. This is called "duck typing". http://c2.com/cgi/wiki?DuckTyping For example, the Python docs often talk about a "file-like object". A file-like object is any object that implements enough of the file protocol to act like a file. In some contexts, it might be enough to implement a read() method; in other contexts, the full file protocol might be needed. The StringIO module contains a class that implements a file-like wrapper around a memory buffer. An instance of StringIO can be passed to any function that expects an open file. StringIO doesn't inherit from any interface, it just implements the needed functions. Large Python projects seem to need something more formal than this. I think Zope, Twisted and PEAK have all invented ways to formalize this notion, and one of them may become part of Python in the future. But for small projects, duck typing and implicit protocols work pretty well. I hope someone else will explain this better than me... Kent _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
