class-method

问题 class MetaData(): maxSize = 2**10 # class definition code if not os.path.exists('sample.data'): SSD = open('sample.data', 'wb+') data = { 0: [], 1: {'.': None,} } data[1]['~'] = data[1] MetaData.save() # i want to call the save function here # class function @classmethod def save(cls): cls.SSD.seek(0) cls.SSD.write(b' ' * cls.maxSize) cls.SSD.seek(0) cls.SSD.write(pickle.dumps(cls.data)) I want to use the save() function inside the class block. I've tried MetaDate.save() and simply save()

问题 I am learning iOS programming and am confused by the following code regarding the use of keyword self. From my understanding, self is like Java's this . It refers to the current instance. When I want to call a class method, the usual way should be like [PlayingCard validSuits]; But it's also OK to invade a class method on an instance, right? Like [self validSuits]; (I am in the class so self refers to an instance of PlayingCard) But in the following code, it gives error somewhere but looks ok

问题 I am learning iOS programming and am confused by the following code regarding the use of keyword self. From my understanding, self is like Java's this . It refers to the current instance. When I want to call a class method, the usual way should be like [PlayingCard validSuits]; But it's also OK to invade a class method on an instance, right? Like [self validSuits]; (I am in the class so self refers to an instance of PlayingCard) But in the following code, it gives error somewhere but looks ok

问题 I am learning iOS programming and am confused by the following code regarding the use of keyword self. From my understanding, self is like Java's this . It refers to the current instance. When I want to call a class method, the usual way should be like [PlayingCard validSuits]; But it's also OK to invade a class method on an instance, right? Like [self validSuits]; (I am in the class so self refers to an instance of PlayingCard) But in the following code, it gives error somewhere but looks ok

问题 The AddressOf operator works only with methods inside standard .bas modules. I am using the following code to retrieve the addresses of class methods: Option Explicit #If VBA7 Then Private Declare PtrSafe Function DispCallFunc Lib "oleaut32.dll" (ByVal pvInstance As LongPtr, ByVal oVft As LongPtr, ByVal cc As tagCALLCONV, ByVal vtReturn As Integer, ByVal cActuals As Long, ByRef prgvt As Integer, ByRef prgpvarg As LongPtr, ByRef pvargResult As Variant) As Long Private Declare PtrSafe Function

问题 The AddressOf operator works only with methods inside standard .bas modules. I am using the following code to retrieve the addresses of class methods: Option Explicit #If VBA7 Then Private Declare PtrSafe Function DispCallFunc Lib "oleaut32.dll" (ByVal pvInstance As LongPtr, ByVal oVft As LongPtr, ByVal cc As tagCALLCONV, ByVal vtReturn As Integer, ByVal cActuals As Long, ByRef prgvt As Integer, ByRef prgpvarg As LongPtr, ByRef pvargResult As Variant) As Long Private Declare PtrSafe Function

来源： https://stackoverflow.com/questions/42996825/what-are-inheritable-alternative-constructors

问题 This question already has answers here : Calling class staticmethod within the class body? (5 answers) Closed 2 years ago . Let's assume I have a class, with a static method, and I want a class property to be set to the value that this method returns: class A: @staticmethod def foo(): return 12 baz = foo() But doing this I get an error: Traceback (most recent call last): File "<stdin>", line 1, in <module> File "<stdin>", line 5, in A TypeError: 'staticmethod' object is not callable I found a

问题 I have the following code: class ObjectOne(object): @classmethod def print_class_name(cls): print cls.__class__.__name__ def print_class_name_again(self): print self.__class__.__name__ if __name__ == '__main__': obj_one = ObjectOne() obj_one.print_class_name() obj_one.print_class_name_again() The output is: type ObjectOne I would like the output to be: ObjectOne ObjectOne But I would like to keep test_cls as a class method via the @classmethod decorator. How can I accomplish this? 回答1: A

问题 module Country def location puts "location" end def self.included(base) def cities puts "cities" end end def self.extended(base) def animals puts "animals" end end end class Test include Country end class Test2 extend Country end As far as I understand, self.included will be invoked when the module is being included as instance method where as self.extended will be invoked when the module is being extended as static class method. But when I have two class in the same file, why it's not