Python is Only Slow If You Use it Wrong¶

by Avery Pennarun
Google employee
- But this talk has nothing to do with them
- If you apply to google and say his name he get’s money. :)
Trying to talk about bitter

Stuff he’s done¶

bup: Python software doing massive things for real problems
- http://github.com/apenwarr/bup
sshuttle: VPN software tht handles 802..11 g/n speeds in python
- http://github.com/apenwarr/sshuttle

chars = open.file('file').read()
for char in chars:
    ...
    # slow

Use regexes and c modules
No such thing as 100% pure python
forget about SWIG
- writing C modules is easy and integrating them easy too
- SWIG is a code generator for C++
python + C is so far the winning combination
C is simple; Python is simple; PyPy is hard
- The concept behind PyPy is really hard
- Python and C are relatively straightforward compared to the concepts of PyPy

Note

I want to learn how to write C and then add it to my Python work.

for i in xrange(1000000):
    a = '\0'*10000

Sample code in Python
Metric test done in Python, PyPy, Java, C, and Go
- Java: Running this loop takes more memory and more time than CPython!
- PyPy takes about the same time as Python
- C is much faster
- Go is much slower

Three different collection strategies
See his upcoming research paper: Seriously Java, WTF?
Amusingly, the new threaded java system is slower and takes more memory
“Ever notice complex Java programs seem to run slow and take up tons of memory?”

Refcount sometimes fails
Did you know Perl never drops objects?
- This is why you can have memory leaks with it.
- Avoiding this requires a deep understanding of Perl

JUST AVOID IT AT ALL COSTS
Break circular references by hand when you are done
- trees are a good example
- TODO: find out what he meant somehow
Better still: use the weakref module

open('file', 'w').write('hello')
open('file', 'w').write('hello')
# YES!!! Cause Python doesn't do Garbage Collection. refcounting FTW!

With “real” GC you habe to manually manage reosurces:

files

database handlers

sockets

locks

When you are done with a variable, it should go away. It shouldn’t stick around. Predictable behavior!

Note

TODO - find out the missing half of this title