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Python extensions tutorial

Day schedule

TimeActivityTime
930Start0
1215Lunch break165
1315Resume0
1600Tea break (10 minutes)165
1615Resume0
1730End45
Total375
Number of days2
Total minutes750
Total hours12.5

Course schedule

SlotTime (hours)Area
Day 1 morning165Introduction and basics
Day 1 afternoon255
Day 2 morning165
Day 2 afternoon255Packaging and distribution
Total14.

Once registered

  • Contact me for system setup if you need help +919880240460
  • Prerequisites should be done before the training

Course outline

Aims of the course

  • Familiarise with Python/C API
  • Innards of the interpreter

Introduction to extensions

  • Why
  • When
  • How

Structure of the course

  • What we aim to do (libcsv)
  • TDD (using py.test)
  • Packaging
  • Live sessions

Prerequisites

Using libcsv

  • Quick overview of how to use libcsv to parse a “large” CSV file and print out fields.
  • Compile and run a few programs to display information as well as print data

Organisation

  • _ccsv.so and ccsv.py with the latter for import.
  • Directories and stuff

Structure of a Python module written in C

  • Basics
    • Various structures and what they represent
    • Reference counts
  • Custom types (new classes)
    • Creating a new class
    • Class methods
    • Objects of the class
    • Object methods
    • Exposing elements of the class

Wrapping libcsv

  • Create a file like object with some extra methods
    • Number of lines, column headers etc.
  • Need to redo this based on what’s provided by the libcsv

Wrapping libcsv

  • Remaining parts

Packaging

  • Distutils
  • Packaging the module

Open session

Work notes

C program using libcsv

Things to include

  • Options to the cvs_init function
    • Intialisation and csv_set_opts
  • Callback based parsing. Pass Python functions in here.
  • Changing options
  • Error handling!

Homework

  • Implement writing CSV files

Overall module design.

  • Initialise file like parser object with file name
  • We should be able to do a for i in fp and get back rows.
  • We can change parameters on the fly with a set_something (or descriptors - even better).

Notes on stages

Exceptions

  • Set an exception in a global variable.

Mention -fPIC

Mention csv_fini

Mention problems with the way we’re executing the callback functions

Spend some time on Reference counts.