3. [0] Sets

Sets are implemented as hash table of (unordered) objects, therefore sets are good for get/set/delete/searching items and bad for . Sets do not support indexing, slicing, or other sequence-like behavior.



In [ ]:

    
a = {1, 2, 'a', (1, 2)}
a



In [ ]:

    
print(type(a))



In [ ]:

    
help(a)

3.2. [0] Sets can grow (O(1))



In [ ]:

    
a.add('a')
print(a)

3.3. [0] Sets can not contain dupplicate objects



In [ ]:

    
a.add('a')
print(a)

3.4. [1] Sets can not contain mutable objects

Mutable objects can not be hashed :-(



In [ ]:

    
a = set()
a.add([1,2]) # Sets can not contain lists



In [ ]:

    
a = set() # Empty set
a.add({1,2,3}) # Sets can not contain sets

3.5 [0] Intersection of sets (O(min(len(s), len(t)))



In [ ]:

    
a = {1,2,3}
b = {2,3,4}
a.intersection(b)

3.6 [0] Union of sets (O(len(s)+len(t)))



In [ ]:

    
a.union(b)

3.7. [0] Sets are MUCH more efficient for searching by content than lists



In [ ]:

    
a = set(range(1000))
print(a)



In [ ]:

    
%timeit '0' in a



In [ ]:

    
a = list(range(1000))
print(a)



In [ ]:

    
%timeit '0' in a

Table of Contents