The problem I see with your blacklist is that in Python, one could write Python code that generates additional Python code, and then run the additional code. So one could generate the word 'eval' from inside of a program that itself doesn't contain the word.

The Computer Science Theory way of accepting a valid string is by constructing a grammar, and then using a grammar parser.

https://en.wikipedia.org/wiki/Formal_grammar

You'd need to understand how grammar parsers work in order to construct one. However, in this case your grammar parser would be a subset of python's grammar parser itself, so it would be a lot of work, if you had unlimited resources I'd go for it but otherwise don't pick this solution.

The problem I see with your blacklist is that in Python, one could write Python code that generates additional Python code, and then run the additional code. So one could generate the word 'eval' from inside of a program that itself doesn't contain the word. Part of the problem is the dynamism of Python itself, whereas a more strongly typed, static language might be safer.

The Computer Science Theory way of accepting a valid string is by constructing a grammar, and then using a grammar parser.

https://en.wikipedia.org/wiki/Formal_grammar

You'd need to understand how grammar parsers work in order to construct one. However, in this case your grammar parser would be a subset of python's grammar parser itself, so it would be a lot of work, if you had unlimited resources I'd go for it but otherwise don't pick this solution.