python - Is the `id()` of a variable associated to the value assigned to it after the variable lifetime finishes? -

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i tinkering objects' identity in python following code:

def f(var1):     print 'within f , before modification: var1= '+str(var1)+', id= '+str(id(var1))     var1 = 10     print 'within f , after modification: var1= '+str(var1)+', id= '+str(id(var1))  def f2(var1):     print 'within f , before modification: var1= '+str(var1)+', id= '+str(id(var1))     var1 = 1     print 'within f , after modification: var1= '+str(var1)+', id= '+str(id(var1))  def f3(var1):     print 'within f , before modification: var1= '+str(var1)+', id= '+str(id(var1))     var1 = 10     print 'within f , after modification: var1= '+str(var1)+', id= '+str(id(var1))   var = 5  print '\n f - var1=10:' print 'before function call: var= '+str(var)+', id= '+str(id(var)) f(var) print 'after function: var= '+str(var)+', id= '+str(id(var))  print '\n f2 - var1=1:' var = [4,3,1,6] print 'before function call: var= '+str(var)+', id= '+str(id(var)) f2(var) print 'after function: var= '+str(var)+', id= '+str(id(var))  print '\n f3 - var1=10 again:' var = 7 print 'before function call: var= '+str(var)+', id= '+str(id(var)) f3(var) print 'after function: var= '+str(var)+', id= '+str(id(var))  print '\n f2 - var1=1 again:' var='a' print 'before function call: var= '+str(var)+', id= '+str(id(var)) f2(var) print 'after function: var= '+str(var)+', id= '+str(id(var))

output:

 f - var1=10: before function call: var= 5, id= 18089816 within f , before modification: var1= 5, id= 18089816 within f , after modification: var1= 10, id= 18089696 after function: var= 5, id= 18089816   f2 - var1=1: before function call: var= [4, 3, 1, 6], id= 23884720 within f , before modification: var1= [4, 3, 1, 6], id= 23884720 within f , after modification: var1= 1, id= 18089912 after function: var= [4, 3, 1, 6], id= 23884720   f3 - var1=10 again: before function call: var= 7, id= 18089768 within f , before modification: var1= 7, id= 18089768 within f , after modification: var1= 10, id= 18089696 after function: var= 7, id= 18089768   f2 - var1=1 again: before function call: var= a, id= 140350777144584 within f , before modification: var1= a, id= 140350777144584 within f , after modification: var1= 1, id= 18089912 after function: var= a, id= 140350777144584

i understand identity of object guaranteed unique during lifetime, , 2 objects non-overlapping lifetimes may have same id() value.

from understand can same id() during execution of code different variables, surprised in code same id() values coincide variable values.

i mean same id() value var1=10. same happens assignment var1=1 has own id() value. doing assignment in different functions returns same id().

so question is: python keeping record of previous variables, values , identities after lifetimes have expired?

if in code there variable assignment same value expired variable, python check records of previous expired variables in memory , give priority use same id() same memory values?

i understand little bit more id() values reuse , memory management in python program.

short answer question - python caches integers in range [-5 , 256] .

so whenever var1 = 10 or var1 = 1 , same object integer cache, , why seeing same id in different runs of function.

if try out values greater or equal 257, may able see different results.

a simple example of behavior - 

>>> var1 = 257 >>> var2 = 257 >>> id(var1) 36635792 >>> id(var2) 36636304 >>> var1 = 10 >>> var2 = 10 >>> id(var1) 1642386016 >>> id(var2) 1642386016

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