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If it were a compiled language where I had to wait to run it, I could see that being a big help, but in python I just constantly run the parts of the code I'm e

If it were a compiled language where I had to wait to run it, I could see that being a big help, but in python I just constantly run the parts of the code I'm editing. If there are any typing issues I catch them almost immediately. To be fair, I do set return types in my docstrings, and let the IDE help there. My gripe really stems from using a libraries that check for a type and raise an exception if it doesn't match. Instead of just trying to actually use it and see if that fails. for example If you require a dict because you're going to expect certain keys, but I have a class that has __get_item__ for those keys, it should work fine. If you check the type then you'll fail before you get that far.

kllrnohj 6y ago
Imagine you need to change the type that's passed to a function. You attempt to update all places, but you miss a path that's in an edge case. Static typing would have caught that for you. By waiting until runtime, you've now just potentially shipped a regression. As a code base gets large, it's just not possible/practical to run all possible ways the code you're editing can be reached. Unless you happen to be lucky enough to have 100% unit test coverage, which very few people do, and running that test suite is somehow quick enough to be a practical alternative to static typing.
- dec0dedab0de 6y ago
  If I need to change a type thats passed to a function that already exists and is heavily used, I would either cast the old type to the new type so both work, or create a new function. If I really cared about cleaning it up I would add a deprecation warning when its done the old way.
stevesimmons 6y ago
For doing "duck-typing" formally, you need Interfaces or Protocols, rather than checking from a shortlist of allowed types. Here's a blog post [1] from this discussion on Django 3.2 [2] 10 days ago. [1] https://glyph.twistedmatrix.com/2021/03/interfaces-and-protocols.html https://glyph.twistedmatrix.com/2021/03/interfaces-and-proto... [2] https://news.ycombinator.com/item?id=26710013 https://news.ycombinator.com/item?id=26710013
stevesimmons 6y ago
Actually, this precursor blog post focusing on typing.Protocols is even clearer: https://glyph.twistedmatrix.com/2020/07/new-duck.html https://glyph.twistedmatrix.com/2020/07/new-duck.html

kllrnohj 6y ago

Imagine you need to change the type that's passed to a function. You attempt to update all places, but you miss a path that's in an edge case. Static typing would have caught that for you. By waiting until runtime, you've now just potentially shipped a regression. As a code base gets large, it's just not possible/practical to run all possible ways the code you're editing can be reached. Unless you happen to be lucky enough to have 100% unit test coverage, which very few people do, and running that test suite is somehow quick enough to be a practical alternative to static typing.

dec0dedab0de 6y ago
If I need to change a type thats passed to a function that already exists and is heavily used, I would either cast the old type to the new type so both work, or create a new function. If I really cared about cleaning it up I would add a deprecation warning when its done the old way.

stevesimmons 6y ago

For doing "duck-typing" formally, you need Interfaces or Protocols, rather than checking from a shortlist of allowed types. Here's a blog post [1] from this discussion on Django 3.2 [2] 10 days ago. [1] https://glyph.twistedmatrix.com/2021/03/interfaces-and-protocols.html https://glyph.twistedmatrix.com/2021/03/interfaces-and-proto... [2] https://news.ycombinator.com/item?id=26710013 https://news.ycombinator.com/item?id=26710013

stevesimmons 6y ago

Actually, this precursor blog post focusing on typing.Protocols is even clearer: https://glyph.twistedmatrix.com/2020/07/new-duck.html https://glyph.twistedmatrix.com/2020/07/new-duck.html