Comments on: A foolish consistency, etc http://4.flowsnake.org/archives/122 A Pythoneer's adventures with Chicken Scheme. ^_^ And more. Tue, 06 Jan 2009 19:51:35 +0000 http://wordpress.org/?v=2.6.5 By: rgz http://4.flowsnake.org/archives/122#comment-328 rgz Thu, 19 Jun 2008 23:08:10 +0000 http://4.flowsnake.org/?p=122#comment-328 While I agree that python is being overly conservative and that list should have a length (and a join) method, the reason that Python sequences lack a length method is due to the fact that, length methods are so easy to create in an easy and standarised way that it really does not make sense to write a length method for every sequence ever and yet there is no way to make sure that every sequence will have a length method. Let me elaborate... One of the coolest methods in python is __getitem__ the reason it is so is because by overriding this hook and object gets access to special syntax like >>>item['retrieving'] and >>>for iterating in them: and also... length retrieving. I'm not gonna write it here but its fairly easy to write a __len__ method if an object supports __getitem__, its boilerplate code. And because it's boilerplate code, it got factored into the len() function. it would actually make more sense to factor this function as a method of some BaseSequence class and let the object inherit it from there but the function was easier to implement as a standalone function and so it was done that way. IT IS OLDSCHOOLED but in my opinion it doesn't illustrate that python isn't OO but that Python needed a Sequence base class and enforcing using that class and it failed to do so. While I agree that python is being overly conservative and that list should have a length (and a join) method, the reason that Python sequences lack a length method is due to the fact that, length methods are so easy to create in an easy and standarised way that it really does not make sense to write a length method for every sequence ever and yet there is no way to make sure that every sequence will have a length method. Let me elaborate...

One of the coolest methods in python is __getitem__ the reason it is so is because by overriding this hook and object gets access to special syntax like >>>item['retrieving'] and >>>for iterating in them: and also... length retrieving.

I'm not gonna write it here but its fairly easy to write a __len__ method if an object supports __getitem__, its boilerplate code.

And because it's boilerplate code, it got factored into the len() function.

it would actually make more sense to factor this function as a method of some BaseSequence class and let the object inherit it from there but the function was easier to implement as a standalone function and so it was done that way. IT IS OLDSCHOOLED but in my opinion it doesn't illustrate that python isn't OO but that Python needed a Sequence base class and enforcing using that class and it failed to do so.

]]> By: John Cowan http://4.flowsnake.org/archives/122#comment-326 John Cowan Thu, 19 Jun 2008 17:39:57 +0000 http://4.flowsnake.org/?p=122#comment-326 De facto len() is a method, in the sense that its behavior is polymorphic. It just can't be called with the syntax of a method, which is a wart, but what languages are without warts (except Scheme?) De facto len() is a method, in the sense that its behavior is polymorphic. It just can't be called with the syntax of a method, which is a wart, but what languages are without warts (except Scheme?)

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