In Python 2, this function definition is valid:
def sv( (L, R) ):
return L ^ R
However, in Python 3, a syntax error is returned on the second left parenthesis. I can't figure out why?
How do I instruct Python to accept a tuple as input?
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2 Answers
Tuple parameter unpacking was removed in python 3.
Comments
Function parameters are given as single variable names, so you would do:
def sv(l_r):
l, r = l_r
return l ^ r
If you want to ensure that this is a tuple, you can use type annotations and mypy
from typing import Tuple
def sv(l_r: Tuple[int, int]) -> int:
l, r = l_r
return l ^ r
However this is probably not what you want. Accept two parameters and if you have a tuple to pass in, use the splat operator *.
def sv(l, r):
return l ^ r
tup = (1, 2)
result = sv(*tup)
Note that this sort of pattern matching isn't generally supported by Python as a language feature, unlike some other languages (Haskell comes to mind). What you want to do in Haskell would be:
sv :: Bits a => (a, a) -> a
sv (l, r) = l `xor` r -- Note the pattern match here on `(l, r)`
-- contrast with a two-argument function:
sv' :: Bits a => a -> a -> a
sv' l r = l `xor` r
1 Comment
Adam Smith
@ColinMac I think that
itertools.starmap does that.