In Python, in addition to the list (List), tuple (tuple), the dictionary (dict) and other common container type, are also provided set (SET), deque (the deque) and other data types.
set:
1, the order of addition elements can not be recorded.
2, the elements can not be repeated. (You can use this as a list of elements to weight)
3, the container is variable, the elements may be changed in the container.
4, there is an immutable version - frozenset.
set of built-in methods:
1 >>> [e for e in dir(set) if not e.startswith('_')] 2 ['add', 'clear', 'copy', 'difference', 'difference_update', 'discard', 'intersection',
'intersection_update', 'isdisjoint', 'issubset', 'issuperset', 'pop', 'remove',
'symmetric_difference', 'symmetric_difference_update', 'union', 'update'] 3 >>>
Method set:
<=, Equivalent to calling the issubset () method, determines whether the subset is set in front of the rear set.
> =, Equivalent to calling the issuperset () method, it is determined whether or not a superset of the set of the front of the rear set.
-, equivalent to calling the difference () method, by subtracting the latter in front of the collection set.
&, Equivalent to calling the intersection method for obtaining intersection of two sets.
^, Calculates the exclusive OR of the two sets of results, and is set with two sets of elements by subtracting the intersection.
= {. 1 >>> set_a }
>>> set_a.add (2 ) # additional element is set
>>> SET_A
{ . 1, 2 }
>>> set_a.remove (. 1 ) # remove elements in the set, but when removing an element not present in the collection being given
>>> SET_A
{ 2 }
>>> set_a.remove (. 1 ) # when removing an element not present in the collection being given
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
KeyError: 1
>>> set_a.add(1)
>>> set_a
{ . 1, 2 }
>>> set_a.discard (. 1 ) # remove elements in the set, when removing an element not present in the collection no error
>>> SET_A
{ 2 }
>>> set_a.discard (. 1 ) # Upon removal element in the set does not exist error
>>> SET_A
{ 2 }
>>> set_b = SET () # set to use a constructor to create collections
>>> set_b.add (. 1 )
>>> set_b.add (2 )
>>> set_b.add (. 3 )
>>> SET_A. issubset (set_b) # determines whether to set a subset of the set of b
True
>>> set_a.issuperset (set_b) # determines whether the set is a superset of the set of b
False
Set_c = >>> set_b.difference (SET_A) # subtracting element in the set with a set of b, to obtain a new set of C
>>> set_c
{ . 1,. 3 }
>>> set_b.difference_update (SET_A) # subtracting element in the set with a set of b, change set B
>>> set_b
{1, 3}
>>>
>>> set_c.clear () # Clear the set of elements in c
>>> set_c
set()
>>> set_b.add(2)
>>> set_b
{1, 2, 3}
>>> set_a
{ 2 }
>>> set_c = set_b.intersection (SET_A) # intersection of two sets is calculated to obtain a new set of C
>>> set_c
{ 2 }
>>> set_b.intersection_update (SET_A) # calculate the intersection of two sets of change set B
>>> set_b
{2}
>>> set_b.add(1)
>>> set_b.add(3)
>>> set_a
{2}
>>> set_b
{ . 1, 2,. 3 }
>>> set_a.add (. 4 )
>>> set_c = set_a.union (set_b) # union of two sets is calculated to obtain a new set
>>> set_c
{ . 1, 2,. 3,. 4 }
>>> set_a.update (set_b) # calculates two sets of set and change the set A
>>> SET_A
{1, 2, 3, 4}
>>> set_a
{1, 2, 3, 4}
>>> set_b
{ . 1, 2,. 3 } >>> set_a.isdisjoint (set_b) # determines whether the two sets contain the same elements, if not returns True, otherwise return False.
False
>>> set_b.isdisjoint(set_b)
False
>>> set_b.isdisjoint(set_a)
False
>>> set_a
{1, 2, 3, 4}
>>> set_b
{ . 1, 2,. 3 }
>>> set_a.symmetric_difference (set_b) # Returns the two collection elements of the set do not overlap.
{ . 4 }
>>> set_a.symmetric_difference_update (set_b) # remove additional current collection in a specified set of the same elements, and another set of different elements inserted into the current collection specified
>>> SET_A
{4}
>>>
Double-ended queue (deque):