> This is one of the most useful constructs in all of computer science and Python rejects it due to what amounts to religious belief.
What utter nonsense.
There was extensive discussion, and it ran into the limitations of Python's semantics. Here's a related problem, a common mistake for new Python coders:
x = []
for a in [1, 2, 3]:
x.append(lambda: a)
print([f() for f in x])
It prints [3, 3, 3], of course, because people don't realize all the lambdas are closing over the same 'a'. And there's simply no way around this with the way Python's scoping works.
Read PEP 3103. Every possible implementation was potentially badly misleading to users:
1. Building the dispatch at compile time would result in mysteriously immutable values.
2. Semantics would likely be different outside a function.
3. Or it would sometimes use dispatch and sometimes use if-else chains, leading to inconsistent performance.
4. Or they'd have to add completely new syntax for static data.
If they just made it syntactic sugar for an if-else chain, even that's misleading, because people will invariably be surprised to learn it's not doing a simple dispatch.
There's nothing religious going on here, Python is simply constrained by its original design. If various proposals to add new syntax for static data come to fruition, then a switch statement would make perfect sense and have clear semantics, and they will be glad they didn't try to kludge some half-baked crap together like they did with Enum.
What utter nonsense.
There was extensive discussion, and it ran into the limitations of Python's semantics. Here's a related problem, a common mistake for new Python coders:
It prints [3, 3, 3], of course, because people don't realize all the lambdas are closing over the same 'a'. And there's simply no way around this with the way Python's scoping works.Read PEP 3103. Every possible implementation was potentially badly misleading to users:
1. Building the dispatch at compile time would result in mysteriously immutable values. 2. Semantics would likely be different outside a function. 3. Or it would sometimes use dispatch and sometimes use if-else chains, leading to inconsistent performance. 4. Or they'd have to add completely new syntax for static data.
If they just made it syntactic sugar for an if-else chain, even that's misleading, because people will invariably be surprised to learn it's not doing a simple dispatch.
There's nothing religious going on here, Python is simply constrained by its original design. If various proposals to add new syntax for static data come to fruition, then a switch statement would make perfect sense and have clear semantics, and they will be glad they didn't try to kludge some half-baked crap together like they did with Enum.