--- a/dictionary.org	Tue May 04 16:52:38 2010 +0530
+++ b/dictionary.org	Tue May 04 17:21:12 2010 +0530
@@ -1,114 +1,121 @@
-* Lists
+* Dictionaries
 *** Outline
-***** Lists
-***** Tuples
+***** Dictionaries
+***** Sets
 ***** Arsenal Required
 *** Script
     Welcome friends. 
     
-    In previous tutorial we covered Lists and Tuples and related 
-    functions. In this session we will continue with Python supported
+    In previous tutorial we covered Lists, Tuples and related 
+    functions. In this session we shall continue with Python
     data structures and cover Dictionaries and sets. We have already 
     covered some basics of Dictionaries in session on Statistics. Here
-    we will revisit those concepts and some new ones. 
+    we shall revisit those concepts and some new ones. 
     
-    We give it a name and it should return a corresponding number. 
+    We give it a name and it returns a corresponding number. 
     Dictionaries are just key-value pair. For each 'key' there is
-    corresponding 'value'. In lists we have indexes to access elements,
-    here we have 'key'. 
+    corresponding 'value' associated with it. In lists we use indexes 
+    to access elements, here we use the 'key'. 
     
-    '{}' are used to create Python dictionaries. Lets start by opening 
-    IPython interpreter. Lets create a dictionary say
+    Lets start by opening IPython interpreter. 
+    '{}' are used to create Python dictionaries. Lets create a dictionary say
 
     player = {'Mat': 134,'Inn': 233,
     'Runs': 10823, 'Avg': 52.53}
-    Its dictionary storing statistics of a cricket player.
-    Now to get the 'average' of this player we have to simply write
+    Its a dictionary storing statistics of a cricket player.
+    Here 'Mat', 'Inn' etc are the keys. Now in order to get the 'average' of
+    this player we simply type
     print player['Avg']
     52.53
 
-    To add a new key-value to this dictionary we have to something like
+    To add a new key-value pair to this dictionary we type
     player['Name'] = 'Rahul Dravid'
-    print player    
-    Please remember that Python dictionaries dont maintain the order
-    in which the key-value pair are stored it might change as we add new
-    entries.
+    print player
+    Please note that Python dictionaries don't maintain the order
+    in which the key-value pairs are stored. The order might change
+    as we add new entries.
 
     In dictionaries Duplicate keys are overwritten, that is when we do 
     player['Mat'] = 139
     It wont create a new entry, rather it will simply overwrite previous
-    value with new one. So
+    value with the new one. So
     print player
     will have updated value
 
-    As we covered in one of previous sessions to iterate through lists 
-    we use 'for'. In case of dictionaries we can iterate over them using 
-    'keys' for example
+    As we covered in one of previous sessions 'for' can be used to iterate
+    through lists. The same is possible in case of dictionaries too. We can
+    iterate over them using the 'keys', for example:
     for key in player:
         print key, player[key]
-    We saw how containership works in lists, there we can check if a 
-    value is present in list or not, in case of Dictionaries it works
-    only for keys. so
+    This prints the keys in the dictionary along with their corresponding 
+    values. Notice that the order is not the same as we entered it.
+    
+    We saw how containership works in lists. There we can check if a 
+    value is present in a list or not but in case of Dictionaries we
+    can only check for the containership of the keys. so
     'Inn' in player
     returns True
     'Econ' in Player
     returns False as there is no such 'key'
-    If you try to look or search 'value' it wont work.
-    Dictionaries supports some functions to retrieve keys and values 
-    like
+    If you try to look or search for a 'value' it will not work.
+    Dictionaries support functions to retrieve keys and values 
+    such as
     player.keys()
     returns the list of all 'keys'
     player.values()
     return list of all 'values'    
 
-    Next we shall look at 'sets'. Sets in Python are unordered 
-    collection of unique elements. This data structure comes handy in
+    Now we shall move on to 'sets'. Sets in Python are an unordered 
+    collection of unique elements. This data structure comes in handy in
     situations while removing duplicates from a sequence, and computing 
     standard math operations on sets such as intersection, union, 
     difference, and symmetric difference. 
     
     Lets start by creating a set
     f10 = set([1,2,3,5,8])
-    f10 is set of Fibonacci numbers less then 10
-    lets print value of f10
+    And thats how a set is created.
+    f10 is the set of Fibonacci numbers less than 10
+    lets print the value of f10
     print f10
 
     As we mentioned earlier, these are unordered structure so order of
-    elements are not maintained, and output order is different than 
-    input order. Lets create one more set of all prime numbers less than
-    10
+    elements is not maintained, and output order is different than 
+    input order, just as in dictionaries. Lets create one more set, a set of
+    all prime numbers less than 10
     p10 = set([2,3,5,7])
     print p10.
     
-    To get union of these two sets we use '|' operator
+    To get union of these two sets we use the or '|' operator
     f10 | p10
     
-    For intersection & operator is used:
+    For intersection we use the and '&' operator:
     f10 & p10
     
-    f10 - p10 gives difference between f10 and p10, which is, elements
-    present in f10 but not present in p10.
-    ^ operator gives us symmetric difference that is p10 union f10 minus
-    f10 intersection p10
+    f10 - p10 gives difference between f10 and p10, that is, the set of all elements
+    present in f10 but not in p10.
+    The carat '^' operator gives us the symmetric difference of 2 sets. That is
+    f10 union p10 minus f10 intersection p10
     f10 ^ p10
 
-    To check if a set is super set or subset greater than and lesser than
-    operators can be used
+    To check if a set is the super set or a subset of another set, the greater than 
+    and the lesser than operators are used
     set([2,3]) < p10
     returns True as p10 is superset of given set
     
-    Similar to lists and dictionaries sets also supports containership so
+    Similar to lists and dictionaries, sets also supports containership so
     2 in p10
     returns True as 2 is part of set p10 and 
     4 in p10
     returns False.
     
-    len function works with sets also:
-    len(f10) returns the length, that is 5
-    We can also use 'for' loops to iterate through a set.
+    The 'len' function works with sets also:
+    len(f10) returns the length, which is 5 in this case.
+    We can also use 'for' loops to iterate through a set just as with dictionaries and lists.
     
     With this we come to the end of this tutorial on Dictionaries and 
-    sets. We have covered some of properties of both data types and 
-    functions supported by them. Thank you.
+    sets. We have seen how to initialize dictionaries, how to index them using keys
+    and a few functions supported by dictionaries. We then saw how to initialize
+    sets, perform various set operations and a few functions supported
+    by sets. Hope you have enjoyed it, Thank you.
 
 *** Notes