Python: Is exec always bad practice and if so why not deprecated
python, python-exec
Solution
No, `eval` and related tools are not always bad by any measure.
There are a number of things that only work well when they are expressed as regular functions with regular, positional or keyword arguments (not magic `*args` or `**keywords` args). There's no way to dynamically create a function with a desired set of arguments, except with `eval`.
For a good example of how this can be used, examine the implementation of `collections.namedtuple`. Although it would be possible to create a class factory like that without `eval`, but all of the functions it defines, `__new__` and `_replace` in particular, would have useless help text, and would be a less convenient tool without it. Worse, the non-eval implementation would almost certainly be SLOWER.
Another, more sweeping example of this exact use of `eval` is the fine `decorator` library, which generalizes this practice in a collection of tools that allow you to dynamically create functions with particular function signatures; it uses `eval` internally.
Problem
Can someone think of an example with good practice that uses exec? If there is always a more efficient and secure way to replace exec, why python doesn't deprecate exec?