Python- String processing

Good Morning Boys

I hope Python concepts shared so far are comfortable for you to understand. Its vital that you revisit all the concepts shared so far as they form base for concepts to be taken up in future.
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Today's link for the Google meet is as follows:

Meeting ID

meet.google.com/aao-dywi-mkg

IMPORTANT INSTRUCTIONS:
1.We will be using 2 blogs but the same link to be used to enter the meeting.
2. Separate attendance for all periods.
3. All work to be copied in registers, Exercise to be done as per instructions.

In the beginning, lets take a look at the answers of the questions shared in the exercise yesterday.

EXERCISE
Is there a difference between "Geeta" and 'Geeta'? Justify.


No difference as a string can be either enclosed in a single quotes 

as in 'Geeta' or double quotes as in "Geeta" 

Predict the output of the following:
>>> print("SCS"*5)
SCSSCSSCSSCSSCS
>>> print(("SCS"," ")*5)
('SCS', ' ', 'SCS', ' ', 'SCS', ' ', 'SCS', ' ', 'SCS', ' ')
>>> print("I"+"Love"+"Columbas")
ILoveColumbas
>>> print("I","Love","Columbas")
I Love Columbas
>>> print("I\n"+"Love\n"+"Columbas\n")
I
Love
Columbas
>>> print("I\t"+"Love\t"+"Columbas\t")
I Love Columbas

2. Suppose 
           str='I LOVE COLUMBAS'

Predict the output of the following:

print str          # Prints complete string

Output: I LOVE COLUMBAS

print str[0]       # Prints first character of the string

Output: I

print str[2:5]     # Prints characters starting from 3rd to 5th

Output: LOVE

print str[2:14]    # Prints string starting from 3rd character

Output: LOVE COLUMBAS

print str * 2      # Prints string two times

Output:I LOVE COLUMBASI LOVE COLUMBAS

print str[0:5] + " MUSIC"

I LOV Music

------------------------------------------------------------------------------------Let us begin our session today.

By the end of this session, you will be able to understand and apply the following concepts of Python Strings:

• Accessing values in strings
• Updating strings
• Escape Characters/sequences
• String operators and their impact

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Strings are amongst the most popular types in Python. We can create them simply by enclosing characters in quotes. Python treats single quotes the same as double quotes. Creating strings is as simple as assigning a value to a variable. For example −

var1 = 'Hello World!'
var2 = "Python Programming"

Accessing Values in Strings

Python does not support a character type; these are treated as strings of length one, thus also considered a substring.

To access substrings, use the square brackets for slicing along with the index or indices to obtain your substring. For example −

Live Demo

#!/usr/bin/python

var1 = 'Hello World!'
var2 = "Python Programming"

print "var1[0]: ", var1[0]
print "var2[1:5]: ", var2[1:5]

When the above code is executed, it produces the following result −

var1[0]:  H
var2[1:5]:  ytho

Updating Strings

You can "update" an existing string by (re)assigning a variable to another string. The new value can be related to its previous value or to a completely different string altogether. For example −

Live Demo

#!/usr/bin/python

var1 = 'Hello World!'
print "Updated String :- ", var1[:6] + 'Python'

When the above code is executed, it produces the following result −

Updated String :-  Hello Python

Escape Characters

Following table is a list of escape or non-printable characters that can be represented with backslash notation.

An escape character gets interpreted; in a single quoted as well as double quoted strings.

Backslash notation		Description
\a		Bell or alert
\b		Backspace
\cx		Control-x
\C-x		Control-x
\e		Escape
\f		Formfeed
\n		Newline
\r		Carriage return
\s		Space
\t		Tab
\v		Vertical tab

String Special Operators

Assume string variable a holds 'Hello' and variable b holds 'Python', then −

Operator	Description	Example
+	Concatenation - Adds values on either side of the operator	a + b will give HelloPython
*	Repetition - Creates new strings, concatenating multiple copies of the same string	a*2 will give -HelloHello
[]	Slice - Gives the character from the given index	a[1] will give e
[ : ]	Range Slice - Gives the characters from the given range	a[1:4] will give ell
in	Membership - Returns true if a character exists in the given string	H in a will give 1
not in	Membership - Returns true if a character does not exist in the given string	M not in a will give 1