> When a user is not aware of this new feature and has been implementing
> up to now her/his PYTHONSTARTUP file with the first example given in
> python 3.3 documentation at
> 
> http://docs.python.org/3/library/readline.html?highlight=readline#example
> 
> then each new interactive python 3.4 session reads (appending them)
> both history files which are saved on exit. Thus those files double
> their size after each interactive python 3.4 session and pretty soon
> become few mega bytes long with a python start up time that becomes
> quite noticeable.

Interesting. A way to avoid doing this would be to only load history if
no history is already present. Since the sys.__interactivehook__ is
executed after PYTHONSTARTUP, this would allow the latter to take
precedence.