Automatic Bootstrapping

Modules imported by include have an automatic bootstrapping mechanism: when imported in another process, the required import hook is automatically loaded. This allows un/pickling and transferring objects, without explicitly preparing include in the receiver. The only restriction is that include must be importable before any module code is run.

Disabling Bootstrap Hooks

At times, bootstrapping arbitrary include types is not desired. For example, a public web service may desire to run existing, local configuration code files during startup only. As a simple remedy, individual include types can be disabled.

To disable include types, both a code and environment interface are available:

Environment Variable PY_INCLUDE_DISABLE
A list of include types to disable. Types are indicated by their module name, such as files for the include.files type. Multiple types may be delimited by commas, with optional whitespace. For example, the list files, encoded disables imports from files and encoded source.
Code Interface include.disable() and include.enable()
Functions to disable or enable individual include types. Types may be indicated by a variety of identifiers. See disable() for details.

Bootstrapping Mechanism

Each include corresponds to an include type implementation and namespace. The former provides the actual import machinery, such as hooks and name translation. The later is a namespace module, into which all modules imported by include are inserted.

For each include type, a separate namespace is used. The namespace itself ensures that its include type is installed. Thus, re-importing a module in a separate process first loads its namespace and thus its import machinery.

For example, a file based import is implemented in include.files, and the default namespace is include.mount. When importing a file foo, it is inserted as Re-importing first imports include.mount.files, which in turn installs include.files.