Use of eval in Python
dynamic, eval, python
Solution
`eval` and `exec` are handy quick-and-dirty way to get some source code dynamically, maybe munge it a bit, and then execute it -- but they're hardly ever the best way, especially in production code as opposed to "quick-and-dirty" prototypes &c.
For example, if I had to deal with such dynamic Python sources, I'd reach for the ast module -- `ast.literal_eval` is MUCH safer than `eval` (you can call it directly on a string form of the expression, if it's a one-off and relies on simple constants only, or do `node = ast.parse(source)` first, then keep the `node` around, perhaps munge it with suitable visitors e.g. for variable lookup, then `literal_eval` the node) -- or, once having put the node in proper shape and vetted it for security issues, I could `compile` it (yielding a code object) and build a new function object out of that. Far less simple (except that `ast.literal_eval` is just as simple as `eval` for the simplest cases!) but safer and preferable in production-quality code.
For many tasks I've seen people (ab-)use `exec` and `eval` for, Python's powerful built-ins, such as `getattr` and `setattr`, indexing into `globals()`, &c, provide preferable and in fact often simpler solutions. For specific uses such as parsing JSON, library modules such as `json` are better (e.g. see SilentGhost's comment on tinnitus' answer to this very question). Etc, etc...
Problem
There is an `eval()` function in Python I stumbled upon while playing around. I cannot think of a case when this function is needed, except maybe as syntactic sugar. What could an example be?