Basic Python and python tutorials

Basic Python and python tutorials

Records Study Notes

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1. _ getitem _ (self, key) built-in method (Build-in)

Example:

 1 class Test(object): 2  3     def __getitem__(self, key): 4  5         print("test") 6  7         return 1 8  9 10 11 t = Test()12 13 print(t["m"])

 

Running result:

>>> hello>>> 1

　　

 

2. ___ getattr _ (self, name) built-in method (Build-in)

This method is called when the property value of the object is not found.

Example:

1 class Test(object):2     def __getattr__(self, name):3         print("test")4         return 15 6 t = Test()7 print(t.m)

Running result:

>>> hello>>> 1

 

When the _ getattr _ function is removed, an error indicating that the attribute m does not exist is displayed.

 

3. @ property modifier

This function is used to generate a corresponding getter function.

Instance:

class Test(object):    @property    def name(self):        return self._name    @name.setter    def name(self, name):        self._name = namet = Test()t.name = "hello"print(t.name)

Running result:

>>> hello

 

4. A if condition else B (syntax)

print("1") if __name__=='__main__' else print("2")

 

5. _ enter _ and _ exit _ built-in methods (Build-in)

Used for with statement blocks. When the with statement block is entered, _ enter _ is called __

When leaving the with statement block, call _ exit __

Example:

 1 class test(object): 2     def __enter__(self): 3         print("enter") 4         return self 5     def __exit__(self, type, value, traceback): 6         print("out") 7         del self 8 with test() as m: 9     m.name = 110     print (m.name)

Running result:

>>> enter>>> 1>>> out

 

6. _ iter _ (self) iterator (Build-in)

Obtain an iterator object through the _ iter _ function, and call the next method of the iterator to continuously obtain the next value.

Example:

 1 class test(object): 2     def __init__(self): 3         self.a = 1 4         self.b = 1 5     def __iter__(self): 6         return self 7     def __next__(self): 8         test = self.a + self.b 9         self.a, self.b = self.b, test10         return self.a11     def next(self):12         return self.__next__13 14 for i in test():15     if i > 1000:16         break17     print(i)