set (mathematics)
Features: a collection object is an unordered set of hashable values: collection members can be dictionary keys, and unlike lists and tuples, collections cannot be indexed by number. In addition, elements in a collection cannot be duplicated.
define
set() -> new empty set object
set(iterable) -> new set object
s = {0}
Application: De-weighting
>>> lst1 = [1,1,2,2,3,4,2] >>> list(set(lst1)) [1, 2, 3, 4]
Common Operations
Sets support a number of standard operations, including concatenation|, intersection&, differencing - and symmetric differencing ^
subsets < <= and supersets > >=
Adding, deleting, and clearing operations
See the following code example
>>> lst1 = [1,2]
>>> lst2 = [2,3]
>>> a = set(lst1) #Define the collection
>>> b = set(lst2)
>>> a,b
({1, 2}, {2, 3})
>>> a|b # Take the parallel set
{1, 2, 3}
>>> a&b # Take the intersection
{2}
>>> a-b # Take the difference set
{1}
>>> b-a # Take the difference set
{3}
>>> list(a) # Convert a collection to a list, or to a tuple, e.g. tuple(a) returns (1,2)
[1, 2]
>>> a < b #Subset judgment
False
>>> c = set([1])
>>> c
{1}
>>> c < a #Subset judgment
True
>>> c <= a #Subset judgment
True
>>> d = set([1,2,3])
>>> d > a # Superset judgment
True
>>>
>>> d >= a # Superset judgment
True
>>> a,b
({1, 2}, {2, 3})
>>> a^b # Symmetric difference sets
{1, 3}
>>> c
{1}
>>> d
{1, 2, 3}
>>> a^d # Symmetric difference sets
{3}
>>> s = {0}
>>> type(s)
<class 'set'>
>>>
>>> print(s, len(s)) # Set length
{0} 1
>>> ('1') #Add elements
>>> s
{0, '1'}
>>> ([2,3]) # Add multiple elements
>>> s
{0, 2, 3, '1'}
>>> (2) # Delete the specified element, or report an error if it's not there.
>>> s
{0, 3, '1'}
>>> () #Randomly deleting elements (doesn't seem to help)
0
>>> s
{3, '1'}
>>> (3) # Delete the specified element
>>> s
{'1'}
>>> () # Empty the collection
>>> s
set()