python - Strange behavior of psutil -

i'm using library psutil python 2.7.

consider small program :

import os import psutil  # return memory usage in mb process = psutil.process(os.getpid()) print process.memory_info().rss / float(2 ** 20) 

the memory informations returned program different. can't understand how application, doing time same stuff (here, pretty nothing) cannot have same memory footprint @ each execution.

example (each line different execution) :

• 10.37109375
• 10.37109375
• 10.359375
• 10.41015625
• 10.4140625
• 10.30078125

am missing here ?

measuring memory occupation taking picture of in movement. ps utils not see same size of script+variables, of parts not visible. classes instantiated , destroyed. variables allocated, freed again.

as documentation says, 'garbage' collector common dynamically typed languages such python, runs @ times not synchronous measuring interval, see variations.

worrysome if memory footprint increasing continually - in case we'd have memory 'leakage' (eg. happen if there recursive call occupying ever-increasing resources).

the times program behaves predictably long on (unless write programs microcontrollers). programs run in multitasking environments, programs , operating system continually (and simultaneously) fighting computer's resources.

but modern programs, such python, ruby, perl , others, don't act same each execution. influenced memory have available (which varies because of other programs running).

and mind, it's not 5-line program testing. take line process = psutil.process(os.getpid()). calls os.getpid(), calls operating system's getpid(). result goes psutil.process calls few hundred lines of code. finally, innocent-looking process = has call memory manager reserve memory process, , transfer result there...