CODEWITHSUNDEEP
pythonlistsetappend
Diego
Diego

Reputation: 233

Making a set of sets returns unhashable type: 'list'

S=set()
for i in range(1,100):
    for j in range(1,100):
        for k in range(1,100):
            if i**2+j**2==k**2:
                S.add(([i,j,k]))
print S

and the error is 

TypeError                                 Traceback (most recent call last)
<ipython-input-45-606e3083d711> in <module>()
      4         for k in range(1,100):
      5             if i**2+j**2==k**2:
----> 6                 S.add(([i,j,k]))
      7 print S

TypeError: unhashable type: 'list'

I just want to get all the distinct Pythagorean triples [for me (3,4,5)=(4,3,5)]. That's why I'm doing it with sets, but for some reason I can't append a set to my original set S...

Upvotes: 0

Views: 369

Answers (2)

behold
behold

Reputation: 556

Instead of creating a set of lists, just sort the list and convert to tuples (to avoid dupes):

S=set()
for i in range(1,100):
    for j in range(1,100):
        for k in range(1,100):
            if i**2+j**2==k**2:
                # Notice I've changed squared brackets to round brackets for tuples, and sorted the list, so that duplicates are eliminated.
                S.add(tuple(sorted([i,j,k])))
print(S)

`

I am assuming run time efficiency is not important for now.

Upvotes: 2

recnac
recnac

Reputation: 3744

The element of set need to be hashable, which means immutable, use tuple instead of list. Or you can use a frozenset.

For "get all the distinct Pythagorean triples [for me (3,4,5)=(4,3,5)].", you can restrict the i as smaller one, j as larger one, sample code here:

S = set()
for i in range(1, 100):
    # include i to support i=j case
    for j in range(i, 100):
        for k in range(1, 100):
            if i ** 2 + j ** 2 == k ** 2:
                S.add((i, j, k))

Hope that will help you.

Upvotes: 1

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