I'm having trouble finding a safe way to parse and evaluate user input
in my program.
In my app, I'm using a calculation like this:
(a / b) * 100
The user should be able to override this and their preference is stored
in a configuration file for later use. So I now have a string with the
user defined calculation template, for example:
>>> config.get('custom-calc')
'(a * b) / 10'
I could tell the user the values should be entered like %(a)s and %(b)s
which makes parsing easier I think, because I can do this:
>>> custom_calc = config.get('custom-calc')
>>> custom_calc
'(%(a)s * %(b)s) / 10'
>>> calc_str = custom_calc % {'a': get_value_a(), 'b': get_value_b()}
I should parse this, fill in the values which the program has at that
point and calculate the outcome. What is the safest way?
Timo
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