[Tutor] can i run the last saved input again

[Steven D'Aprano]

On Sat, 24 Jul 2010 06:00:21 pm Alan Gauld wrote:
> "ANKUR AGGARWAL" <coolankur2006 at gmail.com> wrote
>
> > hey this is a crazy question but i want to know it......
> > suppose i have this code
> >
> > a=raw_input("enter the string :")
> > print a
> >
> > now i want to ask is there's any way that python remembers the
> > input i gave
> > it to last time and it just give me the output when i again run
> > python
>
> No that is impossible, python is an interpreter and if it remembered
> its input you would only ever be able to run one program. What you
> want to do is get your program to remember its input, and that is
> possible. It is very important you are clear in your mind what is
> python and what is your code.

You shouldn't have trimmed the rest of Ankur's post, because he clearly 
states he's talking about his program, not Python specifically:

"now i want to ask is there's any way that python remembers the input i 
gave it to last time and it just give me the output when i again run 
python prog.py?????? i mean i dont need to give input again. I just 
need to give input only first time and when i run the prog again it 
will pick up the previous one output is it possible???"

Well, for some definition of "clearly" :)


> You cannot change much in Python(*), you can 
> change anything in your code.

Actually, you can change a lot in Python, but often you shouldn't.

Any module you import, including builtins, can be monkey-patched 
(modified on the fly), although that's rightfully considered to be 
dangerous and best avoided except under very special circumstances.

You can't change syntax, or literals, or a handful of fixed objects like 
None, but otherwise most things in Python can be modified, if you know 
what you're doing and/or silly enough to modify them.

And of course when you start up Python, it reads a number of environment 
variables and config files, which give you an opportunity to have 
Python remember your input from last session. For example, I have a 
very minimal PYTHONSTARTUP file which automatically imports os and sys. 
I had also experimented with having it back-port functionality from 
versions 2.6 to 2.5. Some people use it to customize things like the 
prompt in the interactive interpreter, or install a tab-completion 
module, provide history which survives shutting down the interpreter 
(like most Linux shells already do), or otherwise provide added 
functionality such as that provided by (e.g.) IPython.

http://ipython.scipy.org/moin

So there are plenty of reasons to want Python to remember your input, 
and plenty of ways to do so.



-- 
Steven D'Aprano