什么是python的id函数

id(object)
Return the “identity” of an object. This is an integer (or long integer) which is guaranteed to be 
unique and 
constant for this object during its lifetime. Two objects with non-overlapping lifetimes may have the 
same?id()?value.
CPython implementation detail:?This is the address of the object in memory.

class Obj():
  def __init__(self,arg):
    self.x=arg
if __name__ == '__main__':

  obj=Obj(1)
  print id(obj)    #32754432
  obj.x=2
  print id(obj)    #32754432
   
  s="abc"
  print id(s)     #140190448953184
  s="bcd"
  print id(s)     #32809848
   
  x=1
  print id(x)     #15760488
  x=2
  print id(x)

class Obj():
  def __init__(self,arg):
    self.x=arg
  def __eq__(self,other):
    return self.x==other.x
   
if __name__ == '__main__':
  
  obj1=Obj(1)
  obj2=Obj(1)
  print obj1 is obj2 #False
  print obj1 == obj2 #True
   
  lst1=[1]
  lst2=[1]
  print lst1 is lst2 #False
  print lst1 == lst2 #True
   
  s1='abc'
  s2='abc'
  print s1 is s2   #True
  print s1 == s2   #True
   
  a=2
  b=1+1
  print a is b    #True
   
  a = 19998989890
  b = 19998989889 +1
  print a is b    #False

id([object])

   a = 'runoob'
    id(a)
4531887632
    b = 1
    id(b)
140588731085608