Beginner python set intersection error

Question

rare = (["word1","word4","word5"])
freq = (["word1","word2","word3"])
unique = rare.intersection(freq)
print unique

error: AttributeError: 'list' object has no attribute 'intersection'

Am I not creating the sets correctly? They look like the examples in documentation -- but I can't seem to use normal set methods on them.

What is the proper syntax for creating sets if these are lists?

Solution 1

This way you're not creating sets, just regular lists. Use the set function:

rare = set(["word1","word4","word5"])
freq = set(["word1","word2","word3"])

Maybe you're confusing sets with tuples. A tuple is created with expressions between parenthesis, but you must provide at least a comma:

("this", "is", "a", "tuple")
("anotherone",)

Tuples are like immutable lists, but they're not sets.

Solution 2

You want this:

rare = {"word1", "word4", "word5"}
freq = {"word1", "word2", "word3"}
unique = rare.intersection(freq)
print(unique)

Note that the syntax for set literals has been backported as far as Python 2.7.

Solution 3

On Python 2.7+, this is syntax for intersections using set operators:

>>> rare = {"word1", "word4", "word5"}
>>> freq = {"word1", "word2", "word3"}
>>> rare & freq
{'word1'}

Solution 4

unique = set(rare).intersection(freq)
print(unique)

Solution 5

u can do it like that its shorter i guess :

rare = (["word1","word4","word5"])
freq = (["word1","word2","word3"])
unique = set(rare).intersection(set(freq))
print(unique)

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