Dave Angel wrote:
Ross wrote:
I'm new to python and I'm trying to come up with a function that takes
a given number of players in a game and returns all possible unique
pairings. Here's the code I've come up with so far, but I'm not
getting the output I'd like to:
def all_pairings(players):
cleanlist = []
for i in range(players):
cleanlist.append(i)
return cleanlist
start = 0
follow = start +1
finallist = []
while follow <= len(cleanlist)-1:
for player in cleanlist:
mini = cleanlist[start],cleanlist[follow]
finallist.append(mini)
follow +=1
start+=1
return finallist
If I were to execute the function with all_pairings(4), I want to get
the output [[0,1],[0,2],[0,3],[1,2],[1,3],[2,3]. Instead, I get
[0,1,2,3] with the code I currently have. Can you guys help me out?
Also, if my code is considered ugly or redundant by this community,
can you make suggestions to clean it up?
First problem is the return you have in the middle of the function,
which returns cleanlist. That's why you're getting [0, 1, 2, 3]
Once you fix that, you'll find you have exceptions in the code where
cleanlist[follow] doesn't work if follow is equal to 4.
I'm afraid the code is ugly, and therefore hard to understand or fix.
Let me suggest an approach, rather than just giving you the code. Why
not create a nested for which generates two subscripts between 0 and 4,
then append only those pairs in which the second is strictly greater
than the first. It won't be the quickest, but it will be easy to follow.
No while loop, no explicit incrementing of variables, and in fact no
subscripting of the lists. Just let them supply their own values.
cleanlist = range(players) # no need for any loop, it's
already a list (except in Python 3.0, in which case it's a sequence that
still works just as well)
finallist = []
for i .....:
for j...
if i<j:
append ...
return finallist
Actually, cleanlist[i] == i, so it's pointless. You can do just:
finallist = []
for i in range(players):
for j in range(i + 1, players):
finallist.append((i, j))
or, using list comprehension:
finallist = [(i, j) for i in range(players) for j in range(i + 1,
players)]
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