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Ever need more performance from that amazing python program you wrote?

Or even if you just want to wait less while your Python programs does your math homework for you, PyPy is the solution.

What is PyPy?

I’ll let their documentation do the explaining:

PyPy is a fast, compliant alternative implementation of the Python language (2.7.13 and 3.5.3). It has several advantages and distinct features:

Speed: thanks to its Just-in-Time compiler, Python programs often run faster on PyPy.

Memory usage: memory-hungry Python programs … might end up taking less space than they do in CPython.

Compatibility: PyPy is highly compatible with existing python code. It supports cffi and can run popular python libraries like twisted and django.

Stackless: PyPy comes by default with support for stackless mode, providing micro-threads for massive concurrency.

How do I use this?

If you’re on Ubuntu, it’s really easy. Just run:

sudo apt install pypy

and you’re done. Now, instead of

python program.py


pypy program.py

or, change the shebang to:

#!/usr/bin/env pypy

My tests:

I created a simple factoring program in Python, which I didn’t spend a lot of time optimizing. With the standard, CPython program:

time python factoring.py 900 60
30 and 30

real    0m0.944s
user    0m0.827s
sys     0m0.011s

now, with pypy:

time pypy factoring.py 900 60
30 and 30

real    0m0.498s
user    0m0.076s
sys     0m0.092s

as you can see, the time is nearly cut in half by simply switching to pypy from CPython, without changing any code. PyPy is designed to be compatible with existing python code, and supports many of the highly-used and/or standard python libraries.


There are a few problems with PyPy, however. The biggest one is that in order to enjoy faster run times, your users will also need to have PyPy installed. While this won’t be a problem for many, for people using systems they don’t have admin on (a Mac, for example), they’ll be stuck with the slower CPython. Also, while most programs are compatible, and I have not noticed anything it can’t run, there will likely be at least a few programs that PyPy can’t run.

Sources: PyPy.org

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