Python???freshman02

Posted 2020-12-05

?????????stat   com   ascii   ??????   enumerate   ??????   ??????   ??????   ??????   

???????????????https://docs.python.org/3/library/functions.html?highlight=built#abs

??????????????????

??????1.abs()-????????????

??????2.divmod()-????????????????????????

??????3.max()-????????????????????????????????????????????????????????????????????????

   

1 >>> max(1,2,3) # ??????3????????? ???3???????????????
2 3
3 >>> max(???1234???) # ??????1??????????????????????????????????????????
4 ???4???
5 >>> max(-1,0) # ??????????????????????????????
6 0
7 >>> max(-1,0,key = abs) # ?????????????????????????????????????????????????????????????????????????????????
8 -1

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??????4.min()?????????????????????????????????????????????????????????????????????????????????

??????5.pow()??????????????????????????????????????????????????????????????????

??????6.round()???????????????????????????????????????

??????7.sum()?????????????????????????????????????????????????????????????????????

??????????????????

??????1.bool????????????????????????????????????????????????????????????????????????0?????????????????????False???

??????2.int????????????????????????????????????????????????

??????3.float???????????????????????????????????????????????????

??????4.complex?????????????????????????????????????????????

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??????5.str?????????????????????????????????????????????(?????????)

??????6.bytearray??????????????????????????????????????????????????????

   

1 a = bytes("abcde",encoding="utf-8")
2 # a[0]=50                #TypeError: ???bytes??? object does not support item assignment
3 print(a)                    #b???abcde???
4 print(a.capitalize())   #b???Abcde???
5 b = bytearray("abcde",encoding="utf-8")
6  #?????????????????????(bytes),bytearray??????
7 print( b[1] )              #98
8 b[1]= 50                  #?????????ascii???:50->2,97->a
9 print(b)                    #bytearray(b???a2cde???)       

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??????7.bytes???????????????????????????????????????????????????????????????

??????8.memoryview????????????????????????????????????????????????????????????

??????

1 >>>v = memoryview(b???abcefg???)
2 >>> v[1]
3 98
4 >>> v[-1]
5 103

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??????9.ord?????????Unicode?????????????????????

??????10.chr???????????????????????????Unicode??????

??????11.bin?????????????????????2???????????????

??????12.oct?????????????????????8??????????????????

??????13.hex?????????????????????16??????????????????

??????

 1 >>> ord(???a???)
 2 97
 3 >>> chr(97) #?????????????????????
 4 ???a???
 5 >>> bin(3) 
 6 ???0b11???
 7 >>> oct(10)
 8 ???0o12???
 9 >>> hex(15)
10 ???0xf???

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??????14.tuple????????????????????????????????????????????????

??????15.list????????????????????????????????????????????????

??????16.dict???????????????????????????????????????????????????

1 >>>a={6:2,8:0,1:4,-5:6,99:11,4:22}
2 >>>print( sorted(a.items())  )#  sorted(a)???key??????????????????key???
3 [(-5,6),(1,4),(4,22),(6,2),(8,0),(99,11)]
4 >>>print( sorted(a.items()),key=lambda x:x[1]  )#???value?????????
5 [(8,0),(6,2),(1,4),(-5,6),(99,11),(4,22)]

??????17.set????????????????????????????????????????????????

??????

 1 >>> tuple() #?????????????????????????????????
 2 ()
 3 >>> tuple(???121???) #?????????????????????????????????????????????????????????
 4 (???1???, ???2???, ???1???)
 5 
 6 >>>list() # ?????????????????????????????????
 7 [] 
 8 >>> list(???abcd???) # ?????????????????????????????????????????????????????????
 9 [???a???, ???b???, ???c???, ???d???]
10 
11 >>> dict() # ?????????????????????????????????????????????
12 {}
13 >>> dict(a = 1,b = 2) #  ????????????????????????????????????
14 {???b???: 2, ???a???: 1}
15 >>> dict(zip([???a???,???b???],[1,2])) # ???????????????????????????????????????
16 {???b???: 2, ???a???: 1}
17 >>> dict(((???a???,1),(???b???,2))) # ??????????????????????????????????????????
18 {???b???: 2, ???a???: 1}
19 
20 >>>set() # ?????????????????????????????????
21 set()
22 >>> a = set(range(10)) # ????????????????????????????????????
23 >>> a
24 {0, 1, 2, 3, 4, 5, 6, 7, 8, 9}

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??????18.frozenset?????????????????????????????????????????????????????????

>>> a = frozenset(range(10))
>>> a
frozenset({0, 1, 2, 3, 4, 5, 6, 7, 8, 9})

??????19.enumerate??????????????????????????????????????????

>>> seasons = [???Spring???, ???Summer???, ???Fall???, ???Winter???]
>>> list(enumerate(seasons))
[(0, ???Spring???), (1, ???Summer???), (2, ???Fall???), (3, ???Winter???)]
>>> list(enumerate(seasons, start=1)) #???????????????
[(1, ???Spring???), (2, ???Summer???), (3, ???Fall???), (4, ???Winter???)]

??????20.range??????????????????????????????????????????range??????

>>> a = range(10)
>>> b = range(1,10)
>>> c = range(1,10,3)
>>> a,b,c # ????????????a,b,c
(range(0, 10), range(1, 10), range(1, 10, 3))
>>> list(a),list(b),list(c) # ????????????a,b,c?????????
([0, 1, 2, 3, 4, 5, 6, 7, 8, 9], [1, 2, 3, 4, 5, 6, 7, 8, 9], [1, 4, 7])
>>>

??????21.iter?????????????????????????????????????????????????????????

>>> a = iter(???abcd???) #???????????????
>>> a
<str_iterator object at 0x03FB4FB0>
>>> next(a)
???a???
>>> next(a)
???b???
>>> next(a)
???c???
>>> next(a)
???d???
>>> next(a)
Traceback (most recent call last):
  File "<pyshell#29>", line 1, in <module>
    next(a)
StopIteration

??????22.slice???????????????????????????????????????????????????????????????

>>> c1 = slice(5) # ??????c1
>>> c1
slice(None, 5, None)
>>> c2 = slice(2,5) # ??????c2
>>> c2
slice(2, 5, None)
>>> c3 = slice(1,10,3) # ??????c3
>>> c3
slice(1, 10, 3)

??????23.super??????????????????????????????????????????????????????????????????????????????

#????????????A
>>> class A(object):
    def __init__(self):
        print(???A.__init__???)

#????????????B?????????A
>>> class B(A):
    def __init__(self):
        print(???B.__init__???)
        super().__init__()

#super??????????????????
>>> b = B()
B.__init__
A.__init__

??????24.object?????????????????????object??????

>>> a = object()
>>> a.name = ???kim??? # ??????????????????
Traceback (most recent call last):
  File "<pyshell#9>", line 1, in <module>
    a.name = ???kim???
AttributeError: ???object??? object has no attribute ???name???

??????????????????

??????1.all???????????????????????????????????????????????????True?????????0???True???

>>> all([1,2]) #????????????????????????????????????True?????????True
True
>>> all([0,1,2]) #?????????0???????????????False?????????False
False
>>> all(()) #?????????
True
>>> all({}) #?????????
True
??????

??????2.any?????????????????????????????????????????????True????????????(??????????????????)

??????3.filter???????????????????????????????????????????????????

>>> a = list(range(1,10)) #????????????
>>> a
[1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> def if_odd(x): #????????????????????????
    return x%2==1

>>> list(filter(if_odd,a)) #????????????????????????
[1, 3, 5, 7, 9]

??????4.map???????????????????????????????????????????????????????????????????????????????????????????????????

>>> a = map(ord,???abcd???)
>>> a
<map object at 0x03994E50>
>>> list(a)
[97, 98, 99, 100]

??????5.next????????????????????????????????????????????????

??????6.reversed??????????????????????????????????????????

??????7.sorted????????????????????????????????????????????????????????????

??????8.zip???????????????????????????????????????????????????????????????????????????????????????????????????

1 >>> x = [1,2,3] #??????3
2 >>> y = [4,5,6,7,8] #??????5
3 >>> list(zip(x,y)) # ???????????????3
4 [(1, 4), (2, 5), (3, 6)]

??????????????????

??????1.help??????????????????????????????

??????2.dir??????????????????????????????????????????????????????

??????3.id?????????????????????????????????

??????4.hash???????????????????????????

??????5.type??????????????????????????????????????????????????????????????????????????????

??????6.len????????????????????????

>>> len(???abcd???) # ?????????
>>> len(bytes(???abcd???,???utf-8???)) # ????????????
>>> len((1,2,3,4)) # ??????
>>> len([1,2,3,4]) # ??????
>>> len(range(1,5)) # range??????
>>> len({???a???:1,???b???:2,???c???:3,???d???:4}) # ??????
>>> len({???a???,???b???,???c???,???d???}) # ??????
>>> len(frozenset(???abcd???)) #???????????????

??????7.ascii???????????????????????????????????????????????????

>>> ascii(1)
???1???
>>> ascii(???&???)
"???&???"
>>> ascii(9000000)
???9000000???
>>> ascii(????????????) #???ascii??????
"???\u4e2d\u6587???"

??????8.format?????????????????????

#?????????????????????????????? ???s??? None
>>> format(???some string???,???s???)
???some string???
>>> format(???some string???)
???some string???

#???????????????????????????????????? ???b??? ???c??? ???d??? ???o??? ???x??? ???X??? ???n??? None
>>> format(3,???b???) #??????????????????
???11???
>>> format(97,???c???) #??????unicode?????????
???a???
>>> format(11,???d???) #?????????10??????
???11???
>>> format(11,???o???) #?????????8??????
???13???
>>> format(11,???x???) #?????????16?????? ??????????????????
???b???
>>> format(11,???X???) #?????????16?????? ??????????????????
???B???
>>> format(11,???n???) #???d??????
???11???
>>> format(11) #?????????d??????
???11???

#????????????????????????????????? ???e??? ???E??? ???f??? ???F??? ???g??? ???G??? ???n??? ???%??? None
>>> format(314159267,???e???) #??????????????????????????????6?????????
???3.141593e+08???
>>> format(314159267,???0.2e???) #??????????????????????????????2?????????
???3.14e+08???
>>> format(314159267,???0.2E???) #??????????????????????????????2????????????????????????E??????
???3.14E+08???
>>> format(314159267,???f???) #?????????????????????????????????6?????????
???314159267.000000???
>>> format(3.14159267000,???f???) #?????????????????????????????????6?????????
???3.141593???
>>> format(3.14159267000,???0.8f???) #?????????????????????????????????8?????????
???3.14159267???
>>> format(3.14159267000,???0.10f???) #?????????????????????????????????10?????????
???3.1415926700???
>>> format(3.14e+1000000,???F???)  #???????????????????????????????????????????????????
???INF???

#g?????????????????????????????????p???????????????????????????????????????????????????????????????????????????????????????????????????exp?????????-4<=exp<p???????????????????????????????????????p-1-exp???????????????????????????????????????????????????p-1??????????????????
>>> format(0.00003141566,???.1g???) #p=1,exp=-5 ==??? -4<=exp<p?????????????????????????????????????????????0????????????
???3e-05???
>>> format(0.00003141566,???.2g???) #p=1,exp=-5 ==??? -4<=exp<p?????????????????????????????????????????????1????????????
???3.1e-05???
>>> format(0.00003141566,???.3g???) #p=1,exp=-5 ==??? -4<=exp<p?????????????????????????????????????????????2????????????
???3.14e-05???
>>> format(0.00003141566,???.3G???) #p=1,exp=-5 ==??? -4<=exp<p?????????????????????????????????????????????0???????????????E????????????
???3.14E-05???
>>> format(3.1415926777,???.1g???) #p=1,exp=0 ==??? -4<=exp<p??????????????????????????????????????????0????????????
???3???
>>> format(3.1415926777,???.2g???) #p=1,exp=0 ==??? -4<=exp<p??????????????????????????????????????????1????????????
???3.1???
>>> format(3.1415926777,???.3g???) #p=1,exp=0 ==??? -4<=exp<p??????????????????????????????????????????2????????????
???3.14???
>>> format(0.00003141566,???.1n???) #???g??????
???3e-05???
>>> format(0.00003141566,???.3n???) #???g??????
???3.14e-05???
>>> format(0.00003141566) #???g??????
???3.141566e-05???

??????9.vars??????????????????????????????????????????????????????????????????????????????????????????????????????

??????????????????

• __import__?????????????????????
• isinstance????????????????????????????????????????????????????????????????????????
• issubclass?????????????????????????????????????????????????????????????????????????????????

  >>> issubclass(bool,int)
  True
  >>> issubclass(bool,str)
  False
  
  >>> issubclass(bool,(str,int))
  True

• hasattr?????????????????????????????????

  #?????????A
  >>> class Student:
      def __init__(self,name):
          self.name = name
  
          
  >>> s = Student(???Aim???)
  >>> hasattr(s,???name???) #a??????name??????
  True
  >>> hasattr(s,???age???) #a?????????age??????
  False

• getattr???????????????????????????

  #?????????Student
  >>> class Student:
      def __init__(self,name):
          self.name = name
  
  >>> getattr(s,???name???) #????????????name
  ???Aim???
  
  >>> getattr(s,???age???,6) #???????????????age??????????????????????????????????????????
  
  >>> getattr(s,???age???) #???????????????age????????????????????????????????????
  Traceback (most recent call last):
    File "<pyshell#17>", line 1, in <module>
      getattr(s,???age???)
  AttributeError: ???Stduent??? object has no attribute ???age???

• setattr???????????????????????????

  >>> class Student:
      def __init__(self,name):
          self.name = name
  
          
  >>> a = Student(???Kim???)
  >>> a.name
  ???Kim???
  >>> setattr(a,???name???,???Bob???)
  >>> a.name
  ???Bob???

• delattr????????????????????????

  #?????????A
  >>> class A:
      def __init__(self,name):
          self.name = name
      def sayHello(self):
          print(???hello???,self.name)
  
  #?????????????????????
  >>> a.name
  ????????????
  >>> a.sayHello()
  hello ??????
  
  #????????????
  >>> delattr(a,???name???)
  >>> a.name
  Traceback (most recent call last):
    File "<pyshell#47>", line 1, in <module>
      a.name
  AttributeError: ???A??? object has no attribute ???name???

  
• callable?????????????????????????????????

  >>> class B: #?????????B
      def __call__(self):
          print(???instances are callable now.???)
  
          
  >>> callable(B) #???B??????????????????
  True
  >>> b = B() #?????????B
  >>> callable(b) #??????b??????????????????
  True
  >>> b() #????????????b??????
  instances are callable now.

??????????????????

• globals??????????????????????????????????????????????????????????????????

  >>> globals()
  {???__spec__???: None, ???__package__???: None, ???__builtins__???: <module ???builtins??? (built-in)>, ???__name__???: ???__main__???, ???__doc__???: None, ???__loader__???: <class ???_frozen_importlib.BuiltinImporter???>}
  >>> a = 1
  >>> globals() #????????????a
  {???__spec__???: None, ???__package__???: None, ???__builtins__???: <module ???builtins??? (built-in)>, ???a???: 1, ???__name__???: ???__main__???, ???__doc__???: None, ???__loader__???: <class ???_frozen_importlib.BuiltinImporter???>}

• locals??????????????????????????????????????????????????????????????????

  >>> def f():
      print(???before define a ???)
      print(locals()) #?????????????????????
      a = 1
      print(???after define a???)
      print(locals()) #?????????????????????a???????????????1
  
      
  >>> f
  <function f at 0x03D40588>
  >>> f()
  before define a 
  {} 
  after define a
  {???a???: 1}

• print????????????????????????????????????

  >>> print(1,2,3)
  1 2 3
  >>> print(1,2,3,sep = ???+???)
  1+2+3
  >>> print(1,2,3,sep = ???+???,end = ???=????)
  1+2+3=?

• input????????????????????????

  >>> s = input(???please input your name:???)
  please input your name:Ain
  >>> s
  ???Ain???

 

  ??????????????????

• open????????????????????????????????????????????????????????????????????????

  # t??????????????????b??????????????????
  >>> a = open(???test.txt???,???rt???)
  >>> a.read()
  ???some text???
  >>> a.close()

 

  ??????????????????

• compile????????????????????????????????????AST???????????????????????????exec?????????????????????eval????????????
  

  >>> #??????????????????exec
  >>> code1 = ???for i in range(0,10): print (i)???
  >>> compile1 = compile(code1,??????,???exec???)
  >>> exec (compile1)
  0
  1
  2
  3
  4
  5
  6
  7
  8
  9
  
  
  >>> #????????????????????????eval
  >>> code2 = ???1 + 2 + 3 + 4???
  >>> compile2 = compile(code2,??????,???eval???)
  >>> eval(compile2)
  10

  
• eval????????????????????????????????????????????????????????????????????????????????????

  >>> eval(???1+2+3+4???)
  10

• exec????????????????????????

  >>> exec(???a=1+2???) #????????????
  >>> a
  3

• repr?????????????????????????????????????????????(????????????)

  >>> a = ???some text???
  >>> str(a)
  ???some text???
  >>> repr(a)
  "???some text???"

 

 ?????? ?????????

• property???????????????????????????
  

  >>> class C:
      def __init__(self):
          self._name = ??????
      @property
      def name(self):
          """i???m the ???name??? property."""
          return self._name
      @name.setter
      def name(self,value):
          if value is None:
              raise RuntimeError(???name can not be None???)
          else:
              self._name = value
  
              
  >>> c = C()
  
  >>> c.name # ????????????
  ??????
  >>> c.name = None # ???????????????????????????
  Traceback (most recent call last):
    File "<pyshell#84>", line 1, in <module>
      c.name = None
    File "<pyshell#81>", line 11, in name
      raise RuntimeError(???name can not be None???)
  RuntimeError: name can not be None
  
  >>> c.name = ???Kim??? # ????????????
  >>> c.name # ????????????
  ???Kim???
  
  >>> del c.name # ????????????????????????deleter???????????????
  Traceback (most recent call last):
    File "<pyshell#87>", line 1, in <module>
      del c.name
  AttributeError: can???t delete attribute
  >>> c.name
  ???Kim???

  
• classmethod???????????????????????????????????????
  

  >>> class C:
      @classmethod
      def f(cls,arg1):
          print(cls)
          print(arg1)
  
          
  >>> C.f(??????????????????????????????)
  <class ???__main__.C???>
  ????????????????????????
  
  >>> c = C()
  >>> c.f(????????????????????????????????????)
  <class ???__main__.C???>
  ??????????????????????????????

  
• staticmethod??????????????????????????????????????????
  

  # ?????????????????????????????????
  >>> class Student(object):
      def __init__(self,name):
          self.name = name
      @staticmethod
      def sayHello(lang):
          print(lang)
          if lang == ???en???:
              print(???Welcome!???)
          else:
              print(???????????????)
  
              
  >>> Student.sayHello(???en???) #?????????,???en????????????lang??????
  en
  Welcome!
  
  >>> b = Student(???Kim???)
  >>> b.sayHello(???zh???)  #?????????????????????,???zh????????????lang??????
  zh
  ??????