深入理解Python中的内置常量

>>> True
True
>>> type(True)
<class 'bool'>

>>> True = 1
SyntaxError: can't assign to keyword

>>> False
False
>>> type(False)
<class 'bool'>

>>> False = 0
SyntaxError: can't assign to keyword

>>> None #表示无，没有内容输出
>>> type(None)
<class 'NoneType'>

>>> None = 2
SyntaxError: can't assign to keyword

>>> def sayHello(): #定义函数
 print('Hello')

 
>>> sayHello()
Hello
>>> result = sayHello()
Hello
>>> result
>>> type(result)
<class 'NoneType'>

>>> NotImplemented
NotImplemented
>>> type(NotImplemented)
<class 'NotImplementedType'>

>>> bool(NotImplemented)
True

>>> bool(NotImplemented)
True
>>> NotImplemented = False
>>> 
>>> bool(NotImplemented)
False

>>> class A(object):
 def __init__(self,name,value):
  self.name = name
  self.value = value
 def __eq__(self,other):
  print('self:',self.name,self.value)
  print('other:',other.name,other.value)
  return self.value == other.value #判断2个对象的value值是否相等

>>> a1 = A('Tom',1)
>>> a2 = A('Jay',1)
>>> a1 == a2
self: Tom 1
other: Jay 1
True

>>> class A(object):
 def __init__(self,name,value):
  self.name = name
  self.value = value
 def __eq__(self,other):
  print('self:',self.name,self.value)
  print('other:',other.name,other.value)
  return NotImplemented

>>> a1 = A('Tom',1)
>>> a2 = A('Jay',1)
>>> a1 == a2
self: Tom 1
other: Jay 1
self: Jay 1
other: Tom 1
False

>>> Ellipsis
Ellipsis
>>> type(Ellipsis)
<class 'ellipsis'>
>>> ...
Ellipsis
>>> ... == Ellipsis
True

>>> bool(Ellipsis)
True

>>> bool(Ellipsis)
True
>>> Ellipsis = False
>>> bool(Ellipsis)
False

>>> a = [1,2,3,4]
>>> a.append(a)
>>> a
[1, 2, 3, 4, [...]]
>>> a
[1, 2, 3, 4, [...]]
>>> len(a)
>>> a[4]
[1, 2, 3, 4, [...]]
>>>

>>> __debug__
True
>>> type(__debug__)
<class 'bool'>

>>> __debug__ = False
SyntaxError: assignment to keyword