python: len(x) vs x.__len__() (beginner - intermediate) anthony explains #131

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today I talk about the difference between len(x) and x.__len__() (as well as other similar functions!)

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Почему в Python реализована глобальная функция len() и что об этом говорит Гвидо ван Россум?...

Комментарии
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For anyone interested: For built-in types the CPython implementation of len() returns the value of the ob_size field in the PyVarObject C struct that represents any variable-sized built-in object in memory. Much faster than calling a method. (Fluent Python Book)

alizaini
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Often when doing some data transformation pipeline it's easier to call __dunder__ methods than use functions.
Because you can keep typing forward w/o need to move to begining of line and do arrows/parentheses stuff.

Like

VS:

x * BOL iter( EOL ) * BOL next( EOL ) * BOL len( EOL )

not for production but for jupyter data exploration

tandavme
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Tangentially, I keep seeing people more often use __dict__ instead of vars()

xan
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The shirt... shouldn't it be: "test_allTheThings()" ? .. Maybe even better: "test_all_the_things()"?
Imho, thats how pytest would discover it. But I'd be happy to be corrected. In any case, we should have a video with that test implemented :D

JakubYTb
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Good. I struggle with import paths on windows, that I solve by adding a path to PYTHONPATH, is there a way to avoid doing so? Thanks

optimiserlenergie
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Why do Generators require multiple returns in mypy?

arclight