Shortest code to generate a full mesh of elements

Question

I am trying to find the shortest code that generates a full mesh of the elements fed into it in graphviz format e.g. the full mesh of [0, 1, 2] is:

• 2 -> 0

• 2 -> 1

• 1 -> 0

I have the code below and I think there might be a way to combine the if and for loops, and avoid needing to directly create the empty string

def graph(l):
 if not l:
 return ""
 i = l.pop()
 out = ""
 for z in l:
 out += " {}->{}\n".format(i, z)
 return out + graph(l)
print graph(range(3))

• Grajdeanu Alex: Did you hear about meshpy ? Does it help you ?
• Mark Omo: I'm not trying to generate a mesh in the model sense but a mesh in the network topology sense where every node is connected to every other node, mostly I want to see how mutch smaller I can make the code

Answer 1

If I get it correctly, the shortest way that I can think of is by using itertools.combinations. Basically, you want all unique combinations, so:

from itertools import combinations
def mesh(L):
 return ["->".join(map(str, comb)) for comb in combinations(L, 2)]

Which will return:

['1->2', '1->3', '2->3']

For: mesh([1, 2, 3])

If you then want to print them as above, just:

for x in mesh([1, 2, 3]):
 print(x)