Why do up and down arrow commands not work in the Python command line interpreter?

Question

I am using a VT100 terminal emulator on Linux. In bash, up and down arrows scroll through the last commands executed; they work as expected.

Previous (up arrow) and next (down arrow) commands are not interpreted in the Python command line interpreter. What kind of key mappings do I need to make this work?

Thank you.

Answer 1

By default, the keymappings are:

• older: alt-p
• more recent: alt-n

You can change it in Options -> Configure IDLE -> Keys -> "history-previous" and "history-next" respectively.

Answer 2

I think I've found the answer, assuming you have the GNU Readline library. (This does mean I was partially wrong about the base implementation using a Unix-style interface, as it only does that when GNU Readline [or a port, I guess] isn't available.)

http://docs.python.org/tutorial/interactive.html#history-substitution

History substitution works as follows. All non-empty input lines issued are saved in a history buffer, and when a new prompt is given you are positioned on a new line at the bottom of this buffer. C-P moves one line up (back) in the history buffer, C-N moves one down. Any line in the history buffer can be edited; an asterisk appears in front of the prompt to mark a line as modified. Pressing the Return key passes the current line to the interpreter. C-R starts an incremental reverse search; C-S starts a forward search.