A dictionary is a data type which stores values in pairs. For each element in the dictionary, there is a unique key that points to a value. A dictionary is mutable. It can be changed.
For example:

a_dict = {'one': 1} # Here 'one' is the key.  

Note: The key of a dictionary is immutable. We cannot use a list as a key because a list is mutable. But we can make a tuple of list and use as key.

a_dict['two'] = 2 # Adds key 'two' which points to 2
print a_dict['one']
# prints 1  
if 'three' in a_dict:
    # To check whether a certain string exist as a key in the dictionary  
    print a_dict['three']
else:  
    print "Three not there"
# prints Three not there
del a_dict['one']
# Deletes index 'one' and the value associated with it  
print a_dict
# prints {'two': 2}

Note: A dictionary is unordered. So, only use the keys to navigate through the dictionary.

Solve Problem