how to sorted by summed itemgetter(x)

[Aldarion]

for example, let
from operator import itemgetter
items = [('a', [5, 2]), ('c', [1]), ('b', [6]), ('d', [7])]


sorted(items, key = itemgetter(1))
get this back:
[('c', [1]), ('a', [5, 2]), ('b', [6]), ('d', [7])]

but
sorted(items, key = sum(itemgetter(1)))
raise a errer:
'operator.itemgetter' object is not iterable

how to sorted by summed itemgetter(1)?
maybe sorted(items,key = lambda x:sum(x[1]))
can't itemgetter be used here?

 

[Paul Rubin]

how to sorted by summed itemgetter(1)?
maybe sorted(items,key = lambda x:sum(x[1]))
can't itemgetter be used here?

You really want function composition, e.g.

sorted(items, key=sum*itemgetter(1))

where * is a composition operator (doesn't exist in Python).

You could write:

def compose(f,g):
return lambda *a,**k: f(g(*a,**k))

and then use

sorted(items, key=compose(sum,itemgetter(1)))

or spell it out inline:

sorted(items, key=lambda x: sum(itemgetter(1)(x)))

I'd probably do something like:

snd = itemgetter(1) # I use this all the time
sorted(items, key=lambda x: sum(snd(x)))

 

[Aldarion]

Thanks for the reply,I got it.

how to sorted by summed itemgetter(1)?
maybe sorted(items,key = lambda x:sum(x[1]))
can't itemgetter be used here?

You really want function composition, e.g.

sorted(items, key=sum*itemgetter(1))

where * is a composition operator (doesn't exist in Python).

You could write:

def compose(f,g):
return lambda *a,**k: f(g(*a,**k))

and then use

sorted(items, key=compose(sum,itemgetter(1)))

or spell it out inline:

sorted(items, key=lambda x: sum(itemgetter(1)(x)))

I'd probably do something like:

snd = itemgetter(1) # I use this all the time
sorted(items, key=lambda x: sum(snd(x)))