Ранее я делал серию постов про битовые операторы.
Вот вам ещё один наглядный пример как это используется в Python в модуле re.
Чтобы указать флаг для компилятора нам надо указать его после передаваемой строки. Например, добавляем флаг для игнорирования переноса строки.
pattern = re.compile(r"(\w+)+")
words = pattern.search(text, re.DOTALL)
А как указать несколько флагов? Ведь явно будут ситуации когда нам потребуется больше одного. Кто читал посты по битовые операторы уже понял как.
pattern.search(text, re.DOTALL | re.VERBOSE)
А теперь смотрим исходники, что находится в этих атрибутах?
Не удивительно, степени двойки. Почему? Потому что каждое следующее значение это сдвиг единицы влево.
>>> for n in [1, 2, 4, 8, 16, 32, 64, 128, 256]:
>>>
print(bin(n))
0b1
0b10
0b100
0b1000
0b10000
0b100000
0b1000000
0b10000000
0b100000000
Чтобы было понятней, давайте напишем тоже самое но иначе, добавим ведущие нули:
000000001
000000010
000000100
000001000
000010000
000100000
001000000
010000000
100000000
Не понятно что тут происходит? Читай три поста про битовые операторы начиная с этого ➡️https://t.me/pythonotes/45
В общем, это пример применения побитовых операций в самом Python.
Теперь вы знаете Python еще немного лучше)
#tricks#regex#libs
https://docs.python.org/3/library/functions.html#classmethod
classmethod(function)
Return a class method for function.
A #class method receives the class as implicit first argument, just like an instance method receives the instance. To declare a class method, use this idiom:
class C:
@classmethod
def f(cls, arg1, arg2, ...): ...
The @classmethod form is a function decorator – see the description of function definitions in Function definitions for details.
It can be called either on the class (such as C.f()) or on an instance (such as C().f()). The instance is ignored except for its class. If a class method is called for a derived class, the derived class object is passed as the implied first argument.
Class methods are different than C++ or Java static methods. If you want those, see staticmethod() in this section.
For more information on class methods, consult the documentation on the standard type hierarchy in The standard type hierarchy.
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http://www.wikipython.com/other-concepts/anatomy-of-a-class/
It seems obvious, but note that you must define a class before you use it.
When you create a #class, it establishes its own namespace and all its own local variables (except global definitions) exist only inside that #namespace. They do not interact with other variables of the same name outside it. This leads us to one very important “feature” of classes that you need to know. If you use the same word to designate some specific value both inside and outside the class blueprint, the instance value will take precedence when you try to use that value.
#learn
https://en.wikipedia.org/wiki/Single_responsibility_principle
The #single_responsibility_principle is a computer programming principle that states that every #module or #class should have responsibility over a single part of the functionality provided by the software, and that responsibility should be entirely encapsulated by the class. All its services should be narrowly aligned with that responsibility. Robert C. Martin expresses the principle as, "A class should have only one reason to change."
https://julien.danjou.info/blog/2013/guide-python-static-class-abstract-methods
Mixing #static, #class and #abstract methods
When building classes and inheritances, the time will come where you will have to mix all these methods decorators. So here's some tips about it.
Keep in mind that declaring a method as being abstract, doesn't freeze the prototype of that method. That means that it must be implemented, but it can be implemented with any argument list.