Does Python have an equivalent to 'switch'?

Question

I am trying to check each index in an 8 digit binary string. If it is '0' then it is 'OFF' otherwise it is 'ON'.

Is there a more concise way to write this code with a switch-like feature?

Solution 1

No, it doesn't. When it comes to the language itself, one of the core Python principles is to only have one way to do something. The switch is redundant to:

if x == 1:
    pass
elif x == 5:
    pass
elif x == 10:
    pass

(without the fall-through, of course).

The switch was originally introduced as a compiler optimization for C. Modern compilers no longer need these hints to optimize this sort of logic statement.

Solution 2

Try this instead:

def on_function(*args, **kwargs):
    # do something

def off_function(*args, **kwargs):
    # do something

function_dict = { '0' : off_function, '1' : on_function }

for ch in binary_string:
   function_dict[ch]()

Or you could use a list comprehension or generator expression if your functions return values:

result_list = [function_dict[ch]() for ch in binary_string]

Solution 3

As of Python 3.10.0 (alpha6 released March 30, 2021) there is an official true syntactic equivalent now!

---

digit = 5
match digit:
    case 5:
        print("The number is five, state is ON")
    case 1:
        print("The number is one, state is ON")
    case 0:
        print("The number is zero, state is OFF")
    case _:
        print("The value is unknown")

I've written up this other Stack Overflow answer where I try to cover everything you might need to know or take care of regarding match.

Comments

[Glenn Maynard]

Anyone who thinks Python "only has one way to do something" is very confused.

[Sami Ahmed Siddiqui]

Fixed. I guess I could have claimed that it was python-esque pseudo-code, hehe.

[Daniel Pryden]

@Glenn Maynard: There may be more than one way to do it, but "There should be one -- and preferably only one -- obvious way to do it", per PEP 20 ("The Zen of Python").

[Bastien Léonard]

I believed switch's purpose was to tell the compiler to build a jump table? (I know current compilers don't need this.)

[Sami Ahmed Siddiqui]

@Glenn do understand that while there are many redundant python modules, the actual core language has little in the way of redundant functionality.

[Chris Morgan]

@Soviut: by "angle brackets" I presume you meant "curly braces" (or equivalent, by locale; {} instead of <>)?

[Jason]

the functions are needed to pass variables into scope

[Peter Mortensen]

A switch statement was introduced with Python 3.10 (2021).