# 3 Dynamic Loading

On most modern systems it is possible to configure Python to support dynamic loading of extension modules implemented in C. When shared libraries are used dynamic loading is configured automatically; otherwise you have to select it as a build option (see below). Once configured, dynamic loading is trivial to use: when a Python program executes `import spam`, the search for modules tries to find a file ``spammodule.o`' (``spammodule.so`' when using shared libraries) in the module search path, and if one is found, it is loaded into the executing binary and executed. Once loaded, the module acts just like a built-in extension module.

The advantages of dynamic loading are twofold: the ``core'' Python binary gets smaller, and users can extend Python with their own modules implemented in C without having to build and maintain their own copy of the Python interpreter. There are also disadvantages: dynamic loading isn't available on all systems (this just means that on some systems you have to use static loading), and dynamically loading a module that was compiled for a different version of Python (e.g. with a different representation of objects) may dump core.

- 3.1 Configuring and Building the Interpreter for Dynamic Loading
  - 3.1.1 Shared Libraries
  - 3.1.2 SGI IRIX 4 Dynamic Loading
  - 3.1.3 GNU Dynamic Loading
- 3.2 Building a Dynamically Loadable Module
  - 3.2.1 Shared Libraries
  - 3.2.2 SGI IRIX 4 Dynamic Loading
  - 3.2.3 GNU Dynamic Loading