Roy Smith <r...@panix.com> writes: > Ben Finney <ben+pyt...@benfinney.id.au> wrote: > > > Who says it's frowned on to do work in the initialiser? Where are they > > saying it? That seems over-broad, I'd like to read the context of that > > advice. > > There are some people who advocate that C++ constructors should not do > a lot of work and/or should be incapable of throwing exceptions. The > pros and cons of that argument are largely C++ specific. […] > > But, Python is not C++. I suspect the people who argue for __init__() > not doing much are extrapolating a C++ pattern to other languages > without fully understanding the reason why.
Even simpler: They are mistaken in what the constructor is named, in Python. Python classes have the constructor, ‘__new__’. I would agree with advice not to do anything but allocate the resources for a new instance in the constructor. Indeed, the constructor from ‘object’ does a good enough job that the vast majority of Python classes never need a custom constructor at all. (This is probably why many beginning programmers are confused about what the constructor is called: They've never seen a class with its own constructor!) Python instances have an initialiser, ‘__init__’. That function is for setting up the specific instance for later use. This is commonly over-ridden and many classes define a custom initialiser, which normally does some amount of work. I don't think ‘__init__’ is subject to the conventions of a constructor, because *‘__init__’ is not a constructor*. -- \ “Absurdity, n. A statement or belief manifestly inconsistent | `\ with one's own opinion.” —Ambrose Bierce, _The Devil's | _o__) Dictionary_, 1906 | Ben Finney -- https://mail.python.org/mailman/listinfo/python-list