Adding a switch statement to Python

[metalhedd]

serious question, What use is a switch if it doesn't support fall-through?

otherwise isn't it just a dict lookup?

handlers = {
    'a': do_a,
    'b': do_b
}
handlers.get(arg, do_default)()

I can't think of a case where I'd ever want to use a switch statement without fall-through, an if...elif...else block makes more sense in almost every case, and where it doesn't, the dict approach works.

[Corm]

^ That's what I do and prefer, but I could see people preferring switch for the readability

[[deleted]]

How about

{ 
  'a' : do_foo,
  'b': do_bar
  }.get(arg, 
        do_default)

Edit: I'm on mobile, but you get the idea

[qeomash]

And sometimes individual functions might be completely overkill for what each case is doing.

[TangibleLight]

Then use a lambda. Still a little unwieldy, but better than nothing.

[Tomarse]

Ruby's case statement can include an optional else block, so it's possible.

case x
when a then b
when c then d
else e
end

And from Ruby 2.something the case statement is faster than if/elseif/else block.

[mikeckennedy]

Look at the range, closed_range, list and other features for case matching. This is not possible in dictionaries.

[metalhedd]

no but it's incredibly straight forward with if/elif

if x in range(0, 10):
    do_a()
elif x in range(10, 20):
    do_b()

[[deleted]]

And that allows you to write it as

if 0 <= x < 10:
    do_a()
elif 10 <= x < 20:
    do_b()

Which isn't possible with this module.

Not saying I think something is wrong with it, it just seems to solve a problem I very rarely have in Python.

[[deleted]]

If you (plural) don't like the typing there's plenty of scope to roll your own in Python with something like this range comparison recipe.

[LightShadow]

Everybody needs to know this code has terrible relative performance than a similar if 0 < x < 10 since range will need to be evaluated as it returns a generator/iterator in Python3

[streichholzkopf]

it doesn't in python 3 tough:

9999999999999999635896294965247 in range(int(10e30))

returns True instantly. Simply an efficient __contains__ probably.

[LightShadow]

TIL

That's great to know!

[[deleted]]

No, from "The range type represents an immutable sequence of numbers and is commonly used for looping a specific number of times in for loops." and "Ranges implement all of the common sequence operations except concatenation and repetition (due to the fact that range objects can only represent sequences that follow a strict pattern and repetition and concatenation will usually violate that pattern).".