rlcompleter¶
Word completion for GNU readline.
The completer completes keywords, built-ins and globals in a selectable namespace (which defaults to __main__); when completing NAME.NAME..., it evaluates (!) the expression up to the last dot and completes its attributes.
It’s very cool to do “import sys” type “sys.”, hit the completion key (twice), and see the list of names defined by the sys module!
Tip: to use the tab key as the completion key, call
readline.parse_and_bind(“tab: complete”)
Notes:
- Exceptions raised by the completer function are ignored (and generally cause the completion to fail). This is a feature – since readline sets the tty device in raw (or cbreak) mode, printing a traceback wouldn’t work well without some complicated hoopla to save, reset and restore the tty state.
- The evaluation of the NAME.NAME... form may cause arbitrary application defined code to be executed if an object with a __getattr__ hook is found. Since it is the responsibility of the application (or the user) to enable this feature, I consider this an acceptable risk. More complicated expressions (e.g. function calls or indexing operations) are not evaluated.
- GNU readline is also used by the built-in functions input() and
raw_input(), and thus these also benefit/suffer from the completer features. Clearly an interactive application can benefit by specifying its own completer function and using raw_input() for all its input.
- When the original stdin is not a tty device, GNU readline is never used, and this module (and the readline module) are silently inactive.