How to run id function in python

id(object)

Function: What is returned is the "ID number" of the object, which is unique and unchanged, but the same id value may appear in the non-overlapping life cycle. The object mentioned here should specifically refer to objects of composite types (such as classes, lists, etc.). For types such as strings and integers, the id of the variable changes with the change of the value.

Python version: Python2.x Python3.x

Python official English documentation explains:

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.

Note: The id value of an object in the CPython interpreter represents its address in memory (the interpreter implemented by Python's c language).

Code example:

classObj(): 
 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

When using is to judge whether two objects are equal, the basis is this id value

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

Knowledge point expansion:

Python id() function

description

The id() function returns the unique identifier of the object, which is an integer.

The id() function in CPython is used to obtain the memory address of an object.

grammar

id syntax:

id([object])

Parameter Description:

object — The object.

return value

Returns the memory address of the object.

Instance

The following example shows how to use id:

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

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