import sys
# Demonstrating Strings in Python
# Strings are the simplest and most familiar data structures

# Here is a string constant which we will create 
greeting_statement = "Welcome to Strings in Python"

#Now, let's tell the user to enter his name
print "Can you tell us your name"
# We read the name from STDIN
# rstrip at the end is to eliminate the newline character at the end
input_name = sys.stdin.readline().rstrip()
# Now display the user a customized greeting with his name
# This will show you how strings can be concatenated
print "Demonstrating Concatenation"
print greeting_statement + "," + input_name + "!"

# Now, we will use the multiplication operator to repeat the string five times
print "Demonstrating Replication"
print greeting_statement * 5
# This will display the message Welcome to Strings in Python, five times

#Now we will demonstrate Indexing and Slicing of strings
#x[0] is the first character of the string
#x[1] is the second character of the string
#x[-1] is the last character of the string
#x[-2] is the last-but-one character of the string (or, the second-last character)
#x[1:3] will display the substring of x, from character at index 1 to character at index 3

# Demonstrate Indexes and Slicing of Strings, creating substrings

# Original greeting_statement
print "Original greeting_statement " + greeting_statement

# first character of greeting statement
print "greeting_statement[0]: (first character of greeting statement) "+greeting_statement[0]

# fourth character of greeting statement
print "greeting_statement[3]: (fourth character of greeting statement) "+greeting_statement[3]

# last character
print "greeting_statement[-1]: (last character) " + greeting_statement[-1]

# third-last character
print "greeting_statement[-3]: (third-last character) " + greeting_statement[-3]

# Displays the string from Index 1 to 4
print "greeting_statement[1:4]: (Displays the string from Index 1 to 4) " + greeting_statement[1:4]

# Displays the sub string from first character till index 2 (ie, third character)
print "greeting_statement[:2]: (Displays the string from first character till index 2 (ie, third character)::" + greeting_statement[:2]

# Displays the sub string from index =2  till the end
print "greeting_statement[:2]: (Displays the sub string from index =2  till the end)::" + greeting_statement[2:]

# Displays the length of the string
print "Length of greeting_statement :" + `len(greeting_statement)`

# Splits the string into words, by splitting the string wherever there is a space
print "Splitting the greeting_string into words using split"
print greeting_statement.split(' ')

# Demonstrating Lists in Python 
# Lists are dynamically sized arrays. They are fairly general and can contain any linear sequence of Python objects: functions, strings, integers, floats, objects and also, other lists. It is not necessary that all objects in the list need to be of the same type. You can have a list with strings, numbers , objects; all mixed up. 

# Constructing a basic list
# This list purely has integers
test_list = [1,2,3,4,5,6,7,8,9]
print test_list

# Constructing a mixed list
# This list has integers as well as strings
test_mixed_list = [1,2,3,"test list"]
print "Displaying test_list"
print test_list    
print "Displaying test_mixed_list"
print test_mixed_list


# Appending to a list
test_list.append(10)
# Now the test_list = [1,2,3,4,5,6,7,8,9,10]
print "After appending 10 to the test_list"
print test_list
test_list = test_list + [13,12,11]
# Now the test_list = [1,2,3,4,5,6,7,8,9,10,13,12,11]
print "After adding [13,12,11] to the test list"
print test_list


# Delete from the test_list
del test_list[2]
print "Deleted element at index 2 in the test_list"
# new test list is [1,2,4,5,6,7,8,9,10,13,12,11]
print test_list

# Sorting a list
print "Sorting the test list"
test_list.sort()
print test_list
# This will display [1,2,4,5,6,7,8,9,10,11,12,13]

# Reverse a list
print "Reversting the test_list"
test_list.reverse()
print test_list
# This will display [13,12,11,10,9,8,7,6,5,4,2,1]

# Now we will demonstrate "Multiplying" a list with a constant. I.e, the 
# list will be repeatedly concatenated to itself
list_to_multiply = ['a','b','c']
print "list to multiply"
print list_to_multiply
print "After multiplying this list by 3, i.e. repeating it 3 times:"
product_list = 3 * list_to_multiply
print product_list
# This will display ['a','b','c','a','b','c','a','b','c']

3. Tuples

# Demonstrating Tuples
# Tuples are sequences of immutable Python objects. They are quite similar to lists.
# The difference is, that tuples can't be changed, once creaed. i.e. they are immutable
# Also, tuples use parentheses while Lists use Square Brackers

# Let us declare some tuples to look at the general syntax.

tuple1 = ('history','geography',1,2,3)
tuple2 = (1,10,20,30)
tuple3 = "name","age","qualification"

#Empty tuple
tuple4 = ()

# Tuple with just one element: make sure to use the comma
tuple5 = (10,)

# Accessing values in tuples. Indexing and Slicing.
# Quite similar to Lists.
print "Displaying tuple1"
print tuple1
print "Displaying tuple1[0] ..i.e, the first element of tuple1"
print tuple1[0]
# This will display: history
print "Displaying tuple1[1:3] .. i.e display a subsequence of elements of tuple1"
print tuple1[1:3]
# This will display 10, 20, 30

# Updating Tuples
# We can't update or change existing tuples since they are immutable. 
# However, we can make new tuples out of them
print "Making a new tuple from tuple2 and tuple3"
print "tuple2:"
print tuple2
print "tuple3:"
print tuple3
print "Creating a new tuple4 = tuple2 + tuple3"
tuple4 = tuple2 + tuple3
print "Tuple4:"
print tuple4
# This will print (1,10,20,30,name,age,qualification)

# Python Dictionaries are Hash Tables
# Here, let us create a small telephone number directory where the Keys are the names of people
# and the values are their phone numbers

# General syntax for initializing a dictionary

phone_directory = {"Ankit":"123-56789","Alex":"567-89010","Nina":"345-678910"}

# Accessing Values in the Dictionary
print "***\nDisplaying the values in the phone directory"
print "Ankit's telephone number", phone_directory["Ankit"]
print "Alex's telephone number", phone_directory["Alex"]
print "Nina's telephone number", phone_directory["Nina"]


# Changing and Updating Values in the Dictionary
#As an example, let us change Ankit's Phone Number.
print "***\nNow, updating Ankits phone number to 321 12345"
phone_directory["Ankit"]="321-12345"
# Now let us print it
# You will notice that the phone number stored in the dictionary has changed
# And the new phone number is displayed
print phone_directory

# Removing/deleting dictionary elements
# Let's say, we'd like to remove Alex's phone number
del phone_directory["Alex"]
# Now when we print this dictionary, there will not be any record for Alex
print phone_directory

# Clearing the dictionary
phone_directory.clear()
# All recors will be wiped out from it
print phone_directory
# no key-value pairs left to display

#Deleting the dictionary
del phone_directory

#Once deleted, you can't update, access or display it