Set and Boolean

Sets and Booleans are the two simple object types in python.

Set

A set is an unorderedd collection of unique elements.

We can create a set using set() function.



In [1]:

    
a = set()



In [2]:

    
a









    Out[2]:





set()

Now a is a set. To insert values into a set we use add().



In [3]:

    
a.add(1)



In [4]:

    
a









    Out[4]:





{1}



In [5]:

    
a.add('string')



In [6]:

    
a









    Out[6]:





{1, 'string'}



In [7]:

    
a.add(3.1415)



In [8]:

    
a









    Out[8]:





{1, 3.1415, 'string'}

The values in a set can be of any type. But they should be unique accross the set.



In [9]:

    
a.add(1)



In [10]:

    
a









    Out[10]:





{1, 3.1415, 'string'}

Notice that when we try to add a duplicate value it is not inserted.



In [11]:

    
a.add('string')



In [12]:

    
a









    Out[12]:





{1, 3.1415, 'string'}

Removing an element from a set



In [13]:

    
a.discard(1)



In [14]:

    
a









    Out[14]:





{3.1415, 'string'}

We can use discard() to remove an element from a set permanently. We can also use remove(), but if the value passed is not an element of the set remove returns an error and discard does nothing.



In [15]:

    
a.discard(4)



In [16]:

    
a









    Out[16]:





{3.1415, 'string'}



In [17]:

    
a.remove(4)









    



---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-17-1ace18a8c563> in <module>()
----> 1 a.remove(4)

KeyError: 4

Booleans

Python comes with Booleans (with predefined True and False displays that are basically just the integers 1 and 0). It also has a placeholder object called None.



In [18]:

    
b = True



In [19]:

    
b









    Out[19]:





True

All the comparision operations return boolean.



In [20]:

    
22 > 3









    Out[20]:





True



In [21]:

    
n = 10
n < 100









    Out[21]:





True



In [22]:

    
n > 98









    Out[22]:





False

We can also use None place holder for any object type in python to simply initialize the object with nothing. You can think of it as NULL.



In [23]:

    
b = None



In [24]:

    
b

See there is nothing in b. We can assign any type of value to b.



In [25]:

    
b = 'Sample string'



In [26]:

    
b









    Out[26]:





'Sample string'