1:OS REVIEW:

 1 import sys,os
 2 
 3 # print(sys.argv)   #[a.py,post] can judge post or get
 4 # li = sys.argv
 5 #
 6 # if li[1] == 'post':
 7 #     print('post')
 8 # elif li[1] == 'down':
 9 #     print('1111')
10 
11 #the result:
12 # E:\Python_Projects>cd day27
13 #
14 # E:\Python_Projects\Day27>python os_review post
15 # python: can't open file 'os_review': [Errno 2] No such file or directory
16 #
17 # E:\Python_Projects\Day27>python os_review.py post
18 # post
19 #
20 # E:\Python_Projects\Day27>python os_review.py down
21 # 1111
22 
23 # print(sys.path)
24 # for i in sys.path:
25 #     print(i)
26 # print(sys.version)
27 ##################################################
28 # print(os.getcwd())
29 # os.chdir(r'E:\Python_Projects\Day27')
30 # os.makedirs('dir1\dir2\dir3')
31 # os.removedirs('dir1\dir2\dir3')
32 # print(os.listdir(os.getcwd()))
33 # print(os.stat('os_review.py').st_size) #after the '.' include many functions
34 # os.rename('dir1\dir2\dir3',r'dir1\dir2\aaa')
35 # os.system('dir')
36 # print(os.environ)
37 # print(__file__)   #get the current path's filename
38 # print(os.path.abspath(__file__))
39 # print(os.path.split(os.path.abspath(__file__)))
40 #('E:\\Python_Projects\\Day27', 'os_review.py')
41 # print(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
42 # print(os.path.join(r'd:\\','www','baidu','a.py'))
43 print(os.path.join(os.path.dirname(os.path.abspath(__file__)),'dir1','dir2','123.txt'))
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2:REFLECTION:

 1 #>>>>>>>>>>>>>>>>>>>>reflection of files:
 2 #test.py:
 3 # def say_hi():
 4 #     print('hello')
 5 
 6 # import test as obj
 7 # print(obj)
 8 # print(hasattr(obj,'say_hi'))
 9 # print(hasattr(obj,'say_hiiiiiiiii'))
10 #
11 # if hasattr(obj,'say_hi'):
12 #     func=getattr(obj,'say_hi')
13 #     func()
14 # else:
15 #     print('other logical')
16 
17 #>>>>>>>>>>>>>>>>>>>>judge the content in current file:
18 x=111
19 y=222
20 import sys
21 obj1 = sys.modules[__name__]
22 print(hasattr(obj1,'x'))
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3:GETATTIBUTE ERROR:

 1 class Foo:
 2     def __init__(self, x):
 3         self.x = x
 4 
 5     def __getattr__(self, item):
 6         print('executing __getattr__')
 7 
 8     def __getattribute__(self, item):
 9         print('executing __getattribute__')
10         raise AttributeError('abnormal')   #go to __getattr__:avoid the collapse of the program
11         # raise TabError('xxxxxx')
12 
13 f1 = Foo(10)
14 print(f1.x)       #excuting __getattribute__
15 # f1.xxxx         #excuting __getattribute__
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4:CHANGE THE DISPLAY OF THE OBJECT:

 1 # l = list('hello')
 2 # print(l)
 3 # #['h', 'e', 'l', 'l', 'o']
 4 #
 5 # file = open('test.txt','w')
 6 # print(file)
 7 # <_io.TextIOWrapper name='test.txt' mode='w' encoding='cp936'>
 8 
 9 class Foo:
10     def __init__(self,name,age):
11         self.name = name
12         self.age = age
13 
14     # def __str__(self):
15     #     #   return 'made your own diaplay of the object '
16     #     return 'the name is %s,age is %s'%(self.name,self.age)
17 
18     def __repr__(self):
19         return 'the name is %s,age is %s'%(self.name,self.age)
20 
21 
22 # f1 = Foo()
23 f1 = Foo('alex',18)
24 print(f1)  #str(f1)---->f1.__str__(),if no str will find the __repr__()
25 # <__main__.Foo object at 0x0000000002476B20>
26 # when use the __str__:the name is alex,age is 18
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5:SETITEM;GETITEM AND DELITEM:

 1 #>>>>>>>>>>the three method is just used in dict:use '[]'
 2 
 3 class Foo:
 4     def __getitem__(self, item):
 5         print('getitem')
 6         return self.__dict__[item]
 7 
 8     def __setitem__(self, key, value):
 9         print('setitem')
10         self.__dict__[key] = value
11 
12     def __delitem__(self, key):
13         print('delitem')
14         self.__dict__.pop(key)
15 f1=Foo()
16 print(f1.__dict__)
17 f1['name']='zxver'
18 f1['age']='18'
19 print(f1.__dict__)
20 # {}
21 # setitem
22 # setitem
23 # {}
24 # del f1.name    #did't trigure delitem
25 # print(f1.__dict__)
26 print(f1.age)    #did't trigure setitem
27 del f1['name']   #trigure delitem
28 print(f1.__dict__)
29 print(f1['age'])
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6:THE FORMAT OF THE TIME DISPALYING:

 1 # x= '{0}{0}{0}'.format('dog')
 2 # print(x)
 3 
 4 # '{0.year} {0.mon} {0.day}'
 5 # '{0.year}:{0.mon}:{0.day}'
 6 # '{0.year}-{0.mon}-{0.day}'
 7 format_dic ={
 8 
 9     'ymd':'{0.year} {0.mon} {0.day}',
10     'y:m:d':'{0.year}:{0.mon}:{0.day}',
11     'y-m-d':'{0.year}-{0.mon}-{0.day}',
12 
13 }
14 class Date:
15     def __init__(self,year,mon,day):
16         self.year = year
17         self.mon = mon
18         self.day = day
19 
20     def __format__(self, format_spec):
21         # print('i am execute')
22         # print('--->',format_spec)
23         if not format_spec or format_spec not in format_dic:
24             format_spec = 'ymd'
25         fm = format_dic[format_spec]
26         return fm.format(self)
27 
28 d1 = Date(2020,4,22)
29 # format(d1)
30 print(format(d1,'y-m-d'))
31 print(format(d1,''))
32 print(format(d1,'fgsfhf'))
33 # x = '{0.year} {0.mon} {0.day}'.format(d1)
34 # x = '{0.year}:{0.mon}:{0.day}'.format(d1)
35 # x = '{0.year}-{0.mon}-{0.day}'.format(d1)
36 # print(x)
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7:THE INDEX OF THE FILE:

1 from dir1.dir2.a import C
2 
3 c1 = C('alex')
4 print(c1.name)
5 print(c1.__module__)    #dir1.dir2.a
6 print(c1.__class__)     #<class 'dir1.dir2.a.C'>
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8:IS INSTANCE OR IS SUBCLASS:

 1 class Foo:
 2     pass
 3 
 4 f1 = Foo()
 5 print(isinstance(f1,Foo))
 6 
 7 class Bar(Foo):
 8     pass
 9 # print(issubclass(Bar,Foo))
10 b1 = Bar()
11 print(isinstance(b1,Foo))
12 print(type(b1))  #<class '__main__.Bar'>
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9:ITERABLE FILE:

 1 #>>>>>>>>>>>>>>>>>>>>>>>1:provide a __next__method,use the next or report stopiteration
 2 #>>>>>>>>>>>>>>>>>>>>>>>2:use  the __iter__method to iterize the object
 3 
 4 class Foo:
 5     def __init__(self,n):
 6         self.n = n
 7     def __iter__(self):
 8         return self
 9     def __next__(self):
10         if self.n >= 12:
11             raise StopIteration('stop iteration')
12         self.n += 1
13         return self.n
14 
15 # l=list('hello')
16 # for i in l:
17 #     print(i)
18 
19 f1 = Foo(10)
20 print(f1.__next__())
21 print(f1.__next__())
22 print(f1.__next__())
23 # print(f1.__next__())
24 # print(next(f1))
25 # print(next(f1))
26 # print(next(f1))
27 
28 # for i in f1:  #f1.__iter__() == iter(f1)
29 #     print(i)
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10:SLOTS:#  #use __slot__to replace __dict__ to  save memory of objects:but use it after conider

 1 # class Foo:
 2 #     __slots__=['name','age'] #{'name':None,'age':None}
 3 #     # __slots__ = 'name'
 4 #
 5 # f1=Foo()
 6 # f1.name = 'alex'
 7 # print(f1.name)
 8 # # print(f1.__dict__)  #>>>AttributeError: 'Foo' object has no attribute '__dict__'
 9 # print(f1.__slots__)
10 # f1.age = 17
11 # print(f1.name)
12 # print(f1.age)
13 # # print(f1.gender)  #wrong
14 #
15 # f2=Foo()
16 # print(f2.__slots__)
17 # f2.name='liu'
18 # f2.age=15
19 # print(f2.name)
20 # print(f2.age)
21 # #>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>doc:It can't be herited!
22 # class Foo:
23 #     'hello world!'
24 #     pass
25 # class Bar(Foo):
26 #     pass
27 # print(Bar.__doc__)
28 #
29 # #>>>>>>>>>>>>>>>>>>>>>>>>>>>>>module and class:
30 # #a.py:
31 # # class C:
32 # #     def __init__(self,name):
33 # #         self.name = 'SB'
34 #
35 # # from dir1.dir2.a import C
36 # #
37 # # c1 = C('alex')
38 # # print(c1.name)
39 # # print(c1.__module__)    #dir1.dir2.a
40 # # print(c1.__class__)     #<class 'dir1.dir2.a.C'>
41 #
42 # #>>>>>>>>>>>>>>>>>>>>>>>>__del__:just trigure when delete the class or when the program stop to excute will trigure it
43 # class Foo:
44 #     def __init__(self,name):
45 #         self.name = name
46 #     def __del__(self):
47 #         print('I executing')
48 #
49 # f1 = Foo('alex')
50 # # del f1.name  #>>>>>>'---------->'first
51 # # del f1         #>>>>>>'I executing'first
52 # print('-------------->')     ##>>>>>>'---------->'first,the same with del f1.name
53 # print('-------------->')     ##>>>>>>'---------->'first,the same with del f1.name
54 
55 #>>>>>>>>>>>>>>>>>>>>>>>>__call__:
56 class Foo:
57     # def __init__(self,name):
58     #     self.name = name
59     def __call__(self):
60         print('I executing')
61 
62 f1 = Foo()
63 f1()   #Foo()'s __call__method
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11:斐波那契数列：

 1 class Fib:
 2     def __init__(self):
 3         self._a = 1
 4         self._b = 1
 5 
 6     def __iter__(self):
 7         return self
 8 
 9     def __next__(self):
10         if self._a >100:
11             raise StopIteration('stopiteration')
12         self._a,self._b = self._b,self._a + self._b
13         return self._a
14 
15 f1 = Fib()
16 print(next(f1))
17 print(next(f1))
18 print(next(f1))
19 print(next(f1))
20 print('===========================')
21 for i in f1:
22     print(i)
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12：THE PRIORITY:

#>>>>>>>>>>>>>>>>>>>>the priority :1,class;2,data descriptor;3,instance;
#>>>>>>>>>>>>>>>>>>>>4,nondata descripter == 5,trigure __getattr__()when can't find the attribute