Does the Python standard library have a function that returns the value at index 0? In other words:
zeroth = lambda x: x[0]
I need to use this in a higher-order function like map(). I ask because I believe it's clearer to use a reusable function rather than define a custom one - for example:
pairs = [(0,1), (5,3), ...]
xcoords = map(funclib.zeroth, pairs) # Reusable
vs.
xcoords = map(lambda p: p[0], pairs) # Custom
xcoords = [0, 5, ...] # (or iterable)
I also ask because Haskell does have such a function Data.List.head, which is useful as an argument to higher-order functions:
head :: [a] -> a
head (x:xs) = x
head xs = xs !! 0
xcoords = (map head) pairs
You need to use operator.itemgetter
>>> import operator
>>> pairs = [(0,1), (5,3)]
>>> xcoords = map(operator.itemgetter(0), pairs)
>>> xcoords
[0, 5]
In Python3, map returns a map object, hence you need a list call over it.
>>> list(map(operator.itemgetter(0), pairs))
[0, 5]
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