![]() ![]() The defaultdict class from the collections module can be used to create a dictionary with default values, but it requires a sort of factory function: it needs a callable passed into it that will create those default values. It is very simple to use constructors when dealing with single classes. The list function is also a handy way to make a "factory function" that creates a new empty list. In Python, we create a constructor by defining the init method. ![]() That's by far the most handy reason to use list and I very often see folks forget that list is a great tool for exactly this purpose! Those first three reasons to use list are all about taking an old iterable and making a new list out of it. This use case for list is really just a variation of the last two, but this is an important enough concept that it's worth repeating in 3 different ways! Using list as a factory function Keeping you updated with latest technology trends, Join TechVidvan on. Inherited class is creating a new instance variable instvar1. Python constructors provide you with a way to initialize data attributes within a class. ![]() In fact, many new Pythonistas might assume that readlines would return an iterator ( many built-in functions return iterators after all). In the above example, we are having a constructor in base and inherited class. I’d then use this code to create different types of Bosses: class Boss(object): def init(self, name, attitude, behaviour, face): self.name name self.attitude attitude self.behaviour behaviour self.face face def getattitude(self): return self.attitude def get. With my_file.readlines(), it's not quite as obvious that we're creating a list of lines. I can imagine myself coding up a Boss class similar to the below. With list(my_file), it's clear that we're looping over a file and storing each line in a new list (assuming you know that looping over a file provides lines). ![]()
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