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Jython Registry

Because there is no good platform independent equivalent of the Windows Registry (or Unix environment variables) Java has its own environment variable namespace. Jython acquires its namespace from the following sources (later sources override defaults found in earlier places).

Registry Properties

The following properties are recognized by Jython. More detailed documentation may be found in comments in the registry file provided with the Jython distribution.

python.path Equivalent to CPython’s PYTHONPATH environment variable

python.cachedir The directory to use for caches - currently just package information. This directory must be writable by the user. If the directory is an absolute path, it is used as given, otherwise it is interpreted as relative to sys.prefix.

python.verbose Sets the verbosity level for varying degrees of informative messages. Valid values in order of increasing verbosity are “error”, “warning”, “message”, “comment”, “debug” Normally, Jython can only provide access to public members of classes. If this property is set to false, and you are using a Java version before Java 9, then Jython can access non-public fields, methods, and constructors. This may be deprecated in the future due to Java changes to accessibility from version 9.

python.console The name of a console class. An alternative console class that supports GNU readline can be installed with this property. Jython already include such a console class and it can be enabled by setting this property to org.python.util.ReadlineConsole.

python.console.readlinelib Allow a choice of backing implementation for GNU readline support. Can be either GnuReadline or Editline. This property is only used when python.console is set to org.python.util.ReadlineConsole.

python.startup File to be run at the start of each interactive session, but not when dropping in with the -i flag in after a script has run.

python.modules.builtin Add, remove, or override built in modules.

python.cpython2 Command used to invoke CPython, when needed, as in the case of modules and methods longer than Java supports natively.

Finding the Registry File

The following steps are used to find the Jython registry file, and also to set the Python values for sys.prefix. First a root directory is calculated:

Once the root directory is found, sys.prefix and sys.exec_prefix are set to this, and sys.path has rootdir/Lib appended to it. The registry file used is then rootdir/registry.