Python Sets Quick Reference

In [18]:

    

# create an empty set
empty_set = set()
empty_set


    

    
Out[18]:





set()

In [19]:

    

# create a set directly
languages = {'python', 'r', 'java'}
languages


    

    
Out[19]:





{'java', 'python', 'r'}

In [20]:

    

#create a set from a list
snakes = set(['cobra', 'viper', 'python'])
snakes


    

    
Out[20]:





{'cobra', 'python', 'viper'}

In [21]:

    

len(languages)


    

    
Out[21]:





3

In [22]:

    

'python' in languages


    

    
Out[22]:





True

In [23]:

    

# add a new element
languages.add('sql')
languages


    

    
Out[23]:





{'java', 'python', 'r', 'sql'}

In [24]:

    

# try to add an existing element (ignored, no error)
languages.add('r')
languages


    

    
Out[24]:





{'java', 'python', 'r', 'sql'}

In [25]:

    

# remove an element
languages.remove('java')
languages


    

    
Out[25]:





{'python', 'r', 'sql'}

In [26]:

    

# try to remove a non-existing element (this would throw an error)
# languages.remove('c')


    

In [27]:

    

# remove an element if present, but ignored otherwise
languages.discard('c')
languages


    

    
Out[27]:





{'python', 'r', 'sql'}

In [28]:

    

# remove and return an arbitrary element
languages.pop()


    

    
Out[28]:





'python'

In [29]:

    

# remove all elements
languages.clear()
languages


    

    
Out[29]:





set()

In [30]:

    

# add multiple elements 
languages.update(['go', 'spark'])
languages.update({'spark', 'haskell'})
languages


    

    
Out[30]:





{'go', 'haskell', 'spark'}

In [33]:

    

languages = {'python', 'r', 'java'}
snakes = set(['cobra', 'viper', 'python'])


    

In [34]:

    

# intersection
languages & snakes


    

    
Out[34]:





{'python'}

In [35]:

    

# union
languages | snakes


    

    
Out[35]:





{'cobra', 'java', 'python', 'r', 'viper'}

In [36]:

    

# set difference
languages - snakes


    

    
Out[36]:





{'java', 'r'}