> We enforce the calling convention with code in our library that looks like this: if not isinstance(val, str): raise ValidationException('value must b

> We enforce the calling convention with code in our library that looks like this: if not isinstance(val, str): raise ValidationException('value must be str', val) I love Python, but the more I used it the more I come to see dynamic typing as a mistake. On large projects with shared library code and deeply nested calls, one of the most pervasive problems seems to be wrongly typed data. And building validation exceptions into all of your code seems like a poor solution.