Python programs profiling with decorators

2015-09-06 · 3 min read

[time.time][1] measures overall execution time of a command. It includes time spent by other processes, i.e. it is the time that user notices, so it is not optimal to compare algorithmic efficiency.

import time

start = time.time()

# Code to be profiled goes here

end = time.time()
print('{:.2f}'.format(end - start))


psutil is a python library that provides an interface for retrieving information on running processes. It provides convenient, fast and cross-platform functions to access the memory usage of a Python module:

psutil (python system and process utilities) is a cross-platform library for retrieving information on running processes and system utilization (CPU, memory, disks, network) in Python. It is useful mainly for system monitoring, profiling and limiting process resources and management of running processes. It implements many functionalities offered by command line tools such as: ps, top, lsof, netstat, ifconfig, who, df, kill, free, nice, ionice, iostat, iotop, uptime, pidof, tty, taskset, pmap.

psutil.cpu_percent() Return a float representing the current system-wide CPU utilization as a percentage.

psutil.cpu_count(logical=True)[source] Return the number of logical CPUs in the system (same as os.cpu_count() in Python 3.4).

psutil.virtual_memory()[source] Return statistics about system memory usage total: total physical memory. available: the memory that can be given instantly to processes without the system going into swap.

values = psutil.virtual_memory()

display in MB format

total = >> 20 display in GB format

total = >> 30

RSS (Resident Set Size), which is what most people usually rely on, is misleading because it includes both the memory which is unique to the process and the memory shared with other processes.

What would be more interesting in terms of profiling is the memory which would be freed if the process was terminated right now. In the Linux world this is called USS (Unique Set Size), and this is the major feature which was introduced in psutil 4.0.0 (not only for Linux but also for Windows and OSX).

The USS (Unique Set Size) is the memory which is unique to a process and which would be freed if the process was terminated right now.

import time
import functools
import os
import psutil

examples = []

def example(fn):
    def wrapped():
            print('Running: {}'.format(fn.__name__))

            start = time.time()


            end = time.time()
            print('{:.2f}'.format(end - start))

            process = psutil.Process(os.getpid())
            print('{:.2f} MB\n'.format(process.memory_info().rss / 1024 / 1024))
        except KeyboardInterrupt:

    return wrapped

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