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Programming Python, Second Edition
book

Programming Python, Second Edition

by Mark Lutz
March 2001
Intermediate to advanced content levelIntermediate to advanced
1296 pages
38h 8m
English
O'Reilly Media, Inc.
Content preview from Programming Python, Second Edition

C Extensions Overview

Because Python itself is coded in C today, compiled Python extensions can be coded in any language that is C-compatible in terms of call stacks and linking. That includes C, but also C++ with appropriate “extern C” declarations (which are automatically provided in Python header files). Python extensions coded in a C-compatible language can take two forms:

  • C modules, which look and feel to their clients like Python module files

  • C types, which behave like standard built-in types (numbers, lists, etc.)

Generally, C modules are used to implement flat function libraries, and C types are used to code objects that generate multiple instances. Because built-in types are really just precoded C extension types, your C extension types can do anything that built-in types can: method calls, addition, indexing, slicing, and so on.[143] In the current Python release, though, types are not quite classes -- you cannot customize types by coding a Python subclass unless you add “wrapper” classes as frontend interfaces to the type. More on this later.

Both C modules and types register their operations with the Python interpreter as C function pointers. In all cases, the C layer is responsible for converting arguments passed from Python to C form, and converting results from C to Python form. Python scripts simply import C extensions and use them as though they were really coded in Python; C code does all the translation work.

C modules and types are also responsible for ...

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Publisher Resources

ISBN: 0596000855Supplemental ContentCatalog PageErrata