What does the id() function in Python refer to?

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id() function Used to get the memory address of the object. Many friends don’t know what the id function in python is? Next, the editor will share with you this article to help you learn

The explanation given by the official Python documentation is

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.

It can be seen from this:

1. id(object) returns the "ID card number" of the object , unique and unchanged, but the same id value may appear in non-overlapping life cycles. The objects mentioned here should specifically refer to composite type objects (such as classes, lists, etc.). For types such as strings and integers, the id of the variable changes as the value changes.

2. The id value of an object represents its address in memory in the CPython interpreter. (CPython interpreter: http://zh.wikipedia.org/wiki/CPython)

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)   #15760464

For other orders, use is to judge When two objects are equal, the basis is the id value

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

The difference between is and == is that is is in memory Comparison, and == is a comparison of values

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