Guido van Rossum On Strong vs. Weak Typing

Bill Venners writes "In this interview, Java creator James Gosling says, 'There's a folk theorem out there that systems with very loose typing are very easy to build prototypes with. That may be true. But the leap from a prototype built that way to a real industrial strength system is pretty vast.' In this interview, Python creator Guido van Rossum responds with 'That attitude sounds like the classic thing I've always heard from strong-typing proponents. The one thing that troubles me is that all the focus is on the strong typing, as if once your program is type correct, it has no bugs left. Strong typing catches many bugs, but it also makes you focus too much on getting the types right and not enough on getting the rest of the program correct.'"

Comments

That's a wild-assed statement...

[dozer]

Guido: "Strong typing catches many bugs, but it also makes you focus too much on getting the types right and not enough on getting the rest of the program correct."

Really? Really??? This blanket statement certainly doesn't describe anybody I've worked with. I wonder what information he bases it on...

In a production environment, I've found that writing strongly typed programs always saves time in the long run. It doesn't take much more time and, if you occasionally make a silly mistake (like using == instead of eq in Perl), it can save you hours of aggrivation and headache.

For quick one-offs, of course, losely-typed is always the way to go.

Subjective

[Tablizer]

As somebody who has seen many forum-fights over this issue, I think it is probably subjective. There are complex tradeoffs, and the final score is probably greatly influenced by personal factors. What trips up person A may not trip up person B nearly as much.

I personally like "dynamic" typing. It is easier to read, and it is easier to spot errors that may be missed if there is a lot of formal typing clutter IMO.

However, I think it might be possible to get closer to the best of both worlds by having a "lint"-like utility that points out suspicious usage. For example, it might flag this usage:

x = "foo";
doSomething(x);
y = x + 3; // suspicious line

If you really want it to do that, then you could tell the utility to ignore that particular line to not distract future inspections. (Assume the above language uses a different operator for string concatenation.)