Discussion on: What's a useful programming language feature or concept that a lot of languages don't have?

[Tobias SN]

Switches and cases. I love them. But when I tried out Python, I was really surprised that it didn’t have them, especially since the C# syntax looks a lot like it could be Python. For example, the Python equivelant of

switch(word):
    case(“Hello”):
        otherWord = “World”;
        break;
    case(“World”):
        otherWord = “Hello”;
        break;
    default:
        otherWord = “FooBar”;
        break;

is currently

if word == “Hello”:
    other_word = “World”
elif word == “World”:
    other_word = “Hello”
else:
    other_word = “FooBar”

I know that both PEP 275 and PEP 3103 have been rejected, but I have high hopes that a new one is created and accepted.

[Dustin King]

Maybe it has something to do with having "one way to do it". I never understood the hate for switch/case statements though. It's a little counter-intuitive how they fall through by default in C/C#/C++, but it's still a common thing to want to map a set of possible values to a set of possible actions.

Or return values! Like in Ruby:

    case serial_code
    when /\AC/
      "Low risk"
    when /\AL/
      "Medium risk"
    when /\AX/
      "High risk"
    else
      "Unknown risk"
    end

There's another thing I like from Ruby and Lisp: you don't have to explicitly return, you can just have the return value be whatever the last expression was.

[Tobias SN]

Yeah you’re probably right.

[Moinuddin Quadri]

If you are doing simple task which involves just one statement, instead of using if-elif in Python, you may implement switch statements more elegantly using dictionary.

For example:

def switch(key):
     return {
          'a': 'value_a',
          'b': 'value_b'
    }.get(key, 'value_default')

Sample Run:

>>> switch('a')    # 'a' exists as key
'value_a'
>>> switch('z')    # 'z' doesn't exists as key
'value_default'

Above function will return "value" function corresponding to "key". If "key" not found in dictionary, it will return value as "default_value", just like default in switch statements.

[Tobias SN]

That's not really a switch statement, but more of a dictionary abstraction. In a real switch, you can run code based on the value. If I were to modify your snippet, I'd have to get busy with functions and stuff.