# Writing faster Python

- Institution: CERN
- Department: Developers@CERN Forum
- Speaker: Sebastian Witowski
- Year: 2016
- Language: English
- Subjects: Literature and writing
- Source: [CERN](https://videos.cern.ch/record/3016879)
- Licence: [CERN](http://copyright.web.cern.ch)
- Who can watch: Teens profiles and older (sources give no ratings; placed by Invisible Network from the source's own words)

Did you know that Python preallocates integers from -5 to 257 ? Reusing them 1000 times, instead of allocating memory for a bigger integer, can save you a couple of milliseconds of code's execution time. If you want to learn more about this kind of optimizations then, … well, probably this presentation is not for you :) Instead of going into such small details, I will talk about more "sane" ideas for writing faster code. After a very brief overview of how to optimize Python code (rule 1: don't do this; rule 2: don't do this yet; rule 3: ok, but what if I really want to do this ?), I will show simple and fast ways of measuring the execution time and finally, discuss examples of how some code structures could be improved. You will see:

- What is the fastest way of removing duplicates from a list - How much faster your code is when you reuse the built-in functions instead of trying to reinvent the wheel - What is faster than the good ol' for loop - If the lookup is faster in a list or a set (and when it makes sense to use each) - How the "It's better to beg for forgiveness than to ask for permission" rule works in practice

I will NOT go into details of "serious" optimization, like using different Python implementation or rewriting critical code in C, etc..

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## Lectures

1. [Writing faster Python](https://invisiblenetwork.ai/learn/cern/3016879/1149360ad9ac), 28 min (CERN's player)