Retracing your steps in an interactive python env

[Steven D'Aprano]

On Mon, 14 Sep 2009 14:52:34 -0500, Jack Norton wrote:

> it would be really nice to be
> able to _ask_ python what makes up a def. Something like this (remember
> I am using IPython interactive interpreter session):
> In [0]: def func(input):
> .........:>>>print "im in this function!" + str(input)
> .........:>>>print "doing some stuff" .........:>>>sleep(10)
> 
> Then later on while still in this interactive shell session I could do
> something like:
> In [1]: what_is_in(func)
> "The def for func(input) is:"
> print "im in this function!" + str(input) print "doing some stuff"
> sleep(10)
> 
> and therefore be able to recount what I just did.

Can't be done in the CPython interactive interpreter, because code is 
compiled before being executed. It doesn't save the source code when it 
compiles the function definition, so there's no way it can show you the 
source code. That's why interactive tracebacks don't show you the 
offending line that failed (with the exception of syntax errors) unless 
you have imported the function from a .py file.

You could probably mess about with the readline library to save a copy of 
everything to a history file.

Another alternative is to disassemble the compiled function, and try to 
determine what it does from that. See the dis module.

I wonder whether there's a third party module which will take the output 
of dis.dis and try to reverse engineer Python code from it?



-- 
Steven