Options for set creation

You cannot create an empty set using a literal set (in this case it will not be a set but a dictionary):

In [1]: set1 = {}

In [2]: type(set1)
Out[2]: dict

But an empty set can be created in this way:

In [3]: set2 = set()

In [4]: type(set2)
Out[4]: set

Set from string:

In [5]: set('long long long long string')
Out[5]: {' ', 'g', 'i', 'l', 'n', 'o', 'r', 's', 't'}

Set from list:

In [6]: set([10, 20, 30, 10, 10, 30])
Out[6]: {10, 20, 30}