[PYTHON DB-SIG] Converting strings to numbers

[Jim Fulton]

Hal J Schechner wrote:
> 
> On Wed, 23 Oct 1996, Fredrik Lundh wrote:
> 
> >
> > > This can not only be done from string reps of a number to a numeric
> > > type, but also from string reps of anything (lists, tuples, dicts
> > > etc..) to thier actual type. ( nice for reading plaintext datafiles
> > > ).
> >
> > Note that eval is compact but dangerous; consider the following (on a
> > Unix box):
> >
> >       eval('os.remove("rm -rf ~/*")')
> >
> > Use string.atoi() and string.atof() when you need to be on the safe
> > side.
> >
> 
> This is fine when working with floats or integers, but like I stated, there
> are times (like when trying to restore tuples, lists etc..) when you cant
> use one of the lib functions.  Of course, you would want to make sure you
> are safe when you do it, and making a wrapper would be the 'right' way of
> doing it.  I was only pointing out that it *is* possible to do it ;)

It is worth noting that a safe way to use eval, if you know you don't
need 
to execute any functions is:

  eval(s, {'__builtins__': {}})

This is a "restricted execution" form of eval.

Jim

-- 
Jim Fulton         Digital Creations
jim@digicool.com   540.371.6909
## Python is my favorite language ##
##     http://www.python.org/     ##

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