Nothing Stranger Than This?
· exceptions, finally, implementations, python, try
Originally published at https://holdenweb.blogspot.com/2011/12/nothing-stranger-than-this.html
I’ve just been reading Stack Overflow’s Strangest Language Feature thread, where I discover that (at the time of writing) the highest-voted Python complaint is actually about Java, but the complainant claims that JavaScript and Python are the same. So after I've got this off my chest I'll perhaps go back and look for the top complaint specifically about Python. In Java the complained-of code looks like this:
try {
return true;
} finally {
return false;
}
This naturally translates into
try:
return True
finally:
return False
which, under every recent CPython I've tried (2.{6,7}.X and 3.X), returns False. What I can’t understand is why anyone would expect anything different. If the finally suite contains a return then it’s pretty apparent that the programmer of that function wanted the function to always return a specific value. If there had been code following the return statement would the complainers have expected that to be executed? I'm not sure I see the reason for the complaint at all. What would the complainers have this function return? What is the return statement supposed to do?
This gave rise to a further thought: does a return in a finally clause suppress any active exception? This is only one of a number of exception-handling issues I've been thinking about lately, kind of noodling around the corner cases. More later.
exceptions finally implementations python try