numeric expression from string?

[Diez B. Roggisch]

Brian Blais schrieb:
> Hello,
> 
> I have a string input from the user, and want to parse it to a number, 
> and would like to know how to do it.  I would like to be able to accept 
> arithmetic operations, like:
> 
> '5+5'
> '(4+3)*2'
> '5e3/10**3'
> 
> I thought of using eval, which will work, but could lead to bad security 
> problems (not that it's a big  deal in my app, but still...)
> 
> string.atof won't do the job.  Is there a preferred way of doing this?

No. If you already know about the pro and cons of eval, either go for it 
- or if it bothers you, write a parser using pyparsing and evaluate the 
  expressions yourself.

Regards,

Diez