Book Review: Python Descriptors

About the book:

• Author: Jacob Zimmerman
• ISBN (pbk): 978-1-4842-3726-7
• ISBN (electronic): 978-1-4842-3727-4
• URL: https://link.springer.com/book/10.1007%2F978-1-4842-3727-4

Summery:

This book has two parts:

• First on explaining what descriptors are, data vs non-data ones, and basic implementation of the built in classmethod, staticmethod and property descriptors.

• Second on showing how to implement your custom descriptors.

Highlights:

Chapter 4: Descriptors in the Standard Library

• The property Class

class property:
    def __init__(self, fget=None, fset=None, fdel=None):
        self.fget = fget
        self.fset = fset
        self.fdel = fdel
    def __get__(self, instance, owner):
        if instance is None:
            return self
        elif self.fget is None:
            raise AttributeError("unreadable attribute")
        else:
            return self.fget(instance)
    def __set__(self, instance, value):
        if self.fset is None:
            raise AttributeError("can't set attribute")
        else:
            self.fset(instance, value)
    def __delete__(self, instance):
        if self.fdel is None:
            raise AttributeError("can't delete attribute")
        else:
            self.fdel(instance)
    def getter(self, fget):
        return type(self)(fget, self.fset, self.fdel)
    def setter(self, fset):
        return type(self)(self.fget, fset, self.fdel)
    def deleter(self, fdel):
        return type(self)(self.fget, self.fset, fdel)

• The classmethod descriptor

class classmethod:
    def __init__(self, func):
        self.func = func
    def __get__(self, instance, owner):
        return functools.partial(self.func, owner)

• The staticmethod descriptor

class staticmethod:
    def __init__(self, func):
        self.func = func
    def __get__(self, instance, owner):
        return self.func

Opinion

I enjoyed reading this book, especially the first part, it shows a view port of a developer who is not involved in the core development of python itself. He sometimes also says, ask a core developer if you wanna get the exact reasoning behind it 😄

You don't need an editor open deside you while reading, so I pretty much read it on the bus.

Conclusion:

• Level: Advanced
• I recommend this book for python developer who like to know what is going under the hood, twinkle with the interiors functionality of python, and curious how every thing works.

Go to Top