bug#21077: 24.5; Slow printing in inferior python buffer with python-shell-enable-font-lock

[Rasmus]

Stefan Monnier <monnier@iro.umontreal.ca> writes:

>> It wasn't.  Something is clearly wrong with the regexps involved in
>> this recipe, at least.
>
> The trigger is simple and a well-known problem in Emacs: the command you
> pass to Python outputs one very long line, and Emacs assumes at various places
> that lines aren't too long.  One such assumption is in font-lock itself,
> another appears to be in one of the regexps used in the font-lock config
> of inferior python mode.

The problem is also very much present in the R interface provided by ESS.

The R package data.table has a pretty good solution to long output IMO.
E.g.

R> data.table(x=1:1000000)
                x
       1:       1
       2:       2
       3:       3
       4:       4
       5:       5
      ---        
  999996:  999996
  999997:  999997
  999998:  999998
  999999:  999999
 1000000: 1000000

As I remember Python Pandas does something similar.

Would it be feasible to implement a generalized version of cutting output
for comint-like output if exceeding N lines?

Rasmus

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