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How can I extend a builtin class in python? I would like to add a method to the str class.
I've done some searching but all I'm finding is older posts, I'm hoping someone knows of something newer.
890
Another way to extend (specifically meaning, add new methods, not change existing ones) classes, even built-in ones, is to use a preprocessor that adds the ability to extend out of/above the scope of Python itself, converting the extension to normal Python syntax before Python actually gets to see it.
When you initialize a child class in Python, you can call the super(). __init__() method. This initializes the parent class object into the child class. In addition to this, you can add child-specific information to the child object as well.
As is the case with other programming languages like as Java and C++, polymorphism is implemented in Python for a variety of purposes, most notably Duck Typing, Operator and Method overloading, and Method overriding. This polymorphism may be accomplished in two distinct ways: overloading and overriding.
Just subclass the type
>>> class X(str): ... def my_method(self): ... return int(self) ... >>> s = X("Hi Mom") >>> s.lower() 'hi mom' >>> s.my_method() Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 3, in my_method ValueError: invalid literal for int() with base 10: 'Hi Mom' >>> z = X("271828") >>> z.lower() '271828' >>> z.my_method() 271828 One way could be to use the "class reopening" concept (natively existing in Ruby) that can be implemented in Python using a class decorator. An exemple is given in this page: http://www.ianbicking.org/blog/2007/08/opening-python-classes.html
I quote:
I think with class decorators you could do this:
@extend(SomeClassThatAlreadyExists) class SomeClassThatAlreadyExists: def some_method(self, blahblahblah): stuff Implemented like this:
def extend(class_to_extend): def decorator(extending_class): class_to_extend.__dict__.update(extending_class.__dict__) return class_to_extend return decorator If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
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