Question

I have tried making a switch like statement in python, instead of having a lot of if statements.

The code looks like this:

def findStuff(cds):
    L=[]
    c=0
    for i in range(0, len(cds), 3):
        a=differencesTo(cds[i:i+3])
        result = {
            a[2][0]==1: c=i+1,
            a[2][1]==1: c=i+2,
            a[2][2]==1: c=i+3,
            a[1]==1: L.append((cds[i:i+3], a[0], c))
        } 
    return L

My problem is, that this does not work. (Works with if statements, but this would in my opinion be more pretty).

I have found some examples of switches in Python, and they follow this structure. Can anyone help me?

Answer 1

(a) I fail to see what is wrong with if…elif…else

(b) I assume that python does not have a switch statement for the same reason that Smalltalk doesn’t: it’s almost completely redundant, and in the case where you want to switch on types, you can add an appropriate method to your classes; and likewise switching on values should be largely redundant.

Note: I am informed in the comments that whatever Guido’s reason for not creating a switch in the first place, PEPs to have it added were rejected on the basis that support for adding such a statement is extremely limited. See: http://www.python.org/dev/peps/pep-3103/

(c) If you really need switching behaviour, use a hashtable (dict) to store callables. The structure is:

switch_dict = {
    Foo: self.doFoo,
    Bar: self.doBar,
    }

func = switch_dict[switch_var]
result = func() # or if they take args, pass args