[Idle-dev] The '>>> ' prompt is bad

[Roger Serwy]

On 06/21/2012 04:10 PM, Terry Reedy wrote:
> On 6/21/2012 1:08 PM, Roger Serwy wrote:
>
>> Does allowing the cursor to leave the prompt considered a benefit or a
>> detriment for teaching beginners? The last system I remember using that
>> allowed for the cursor to leave the prompt was a line-number BASIC from
>> the 1980's. I haven't used any interactive systems since then that
>> allowed the cursor to leave the prompt.
>
> Moving the cursor (with keys or mouse) is one way to rerun a previous 
> line. It is also the way to select previous input or output. Windows 
> Command Prompt (CP) gets around freezing the cursor to one line by 
> having a *separate* mouse-only select cursor (box when click, versus 
> underline for entry). That means that one can only correct mistakes 
> *on the same line* with backspace (destructive) or home/left arrow. As 
> near as I can tell, it is impossible to edit a previous line of a 
> multiline statement. Ugh. There is a reason I use Idle as my shell.
I'm not suggesting an implementation of Window's CP behavior, as I find 
it too limited as well. On Linux, up/down arrows at the command prompt 
cycle through the command history. Many other interactive programs 
behave the same way, like Octave, Matlab, R, Python, etc. For some 
reason, IDLE has this very different behavior for its prompt. I opened 
this report a long time ago, which has some discussion along these 
lines: http://bugs.python.org/issue2704

IdleX has the Terminal.py extension included which makes IDLE behave how 
I think it should behave.

> Also note that click on previous *statement* and hit enter copies the 
> entire statement (rather than just one line of a multiline statement) 
> and does not clear the current entry line. (So to rerun a previous 
> multiline statement, one must redo it line by line.)
Alt+P and Alt-N are not discoverable in IDLE, except as a keybinding in 
the configuration dialog. The "shell" menu should have these commands.  
Cycling through the history recovers multi-line commands.
>
> So if I do
> >>> <some non-trivial expression>
> and I decide I want to use the expression as part of another statement 
> (say, assignment) I can do
> >>> a =
> and click enter the expression and I have the assignment statement I 
> want. In CP, one must copy first, jump back with HOME, and then add 'a 
> ='. In Idle, one can also build a statement from more than one 
> previous statement.
>
> >>> expr1
> xxx
> >>> expr2
> yyy
> >>> if <copy expr1> and <copy expr2>: ...
> This is impossible in CP due to erase-before-copy.
>
> In other words, do not cripple Idle the way Windows Prompt is!
>