Python-3.4.3/C2/Getting-started-with-strings/English

'Python/C2/Getting Started with Strings/English'Title of script: Getting Started with Strings

Author: Trupti Kini

Keywords: Python, Ipython

Visual Cue	Narration
Show Slide containing title, name of the production team along with the logo of MHRD	Hello Friends. Welcome to the tutorial on "Getting Started with Strings".
Show Slide Objectives	At the end of this tutorial, you will learn to, Define strings in different ways. Concatenate strings. Print a string repeatedly. Access individual elements of the string.
Show slide System Specifications	To record this tutorial, I am using Ubuntu Linux 16.04 operating system Python 3.4.3 and IPython 5.1.0
Show Slide Pre-requisites	To practise this tutorial, you should know how to run basic Python commands on the ipython console If not, see the pre-requisite Python tutorials on this website.
Show Slide What are Strings? In Python, any character within a single/ double/ triple quotes is a string. 'This is a string' “This is a string too” ‘’’This can be a large string’’’	What are strings? In Python, any character within a single/ double/ triple quotes is a string. For example: Single, double, and triple quotes can be used to denote a string as shown here.
Show Slide What are Strings?	Strings in triple quotes can be written in multiple lines. We can also define empty strings. String is a collection of characters which cannot be modified after it is created.
[Terminal] ipython3	Let us first open the Terminal by pressing Ctrl+Alt+T keys simultaneously. Type ipython3 and press Enter.
[IPython console] %pylab and press Enter.	Let us initialise the pylab package. Type %pylab and press Enter.
[IPython Terminal] Type a = 'Hello, World!'	Let us clear the terminal. We can assign a string to a variable called a. Type a is equal to inside any quotes Hello comma World exclamation mark and Press Enter
[IPython Terminal]	Now let us learn string concatenation. Let us assign strings to variables.
Type x = 'Hello' y = 'World'	Type x is equal to inside quotes Hello Press Enter y is equal to inside quotes World Press Enter
Type z = x + ', ' + y + '!' print(z)	Now, let us add the two strings. z is equal to x plus inside quotes comma plus y plus inside quotes exclamation mark. Press Enter print inside parentheses z Press Enter Here x and y are string variables.
Highlight +	The addition operation performs the concatenation of two strings.
Highlight Hello, World!	Here we can see the output of string concatenation.
Type clear	Let us clear the terminal. What if we multiply a string with an integer? Let us find out!
[IPython Terminal] Press Up arrow till we get x Type x * 5	Recall x string. Press Enter x multiplied by 5 Press Enter
Show Ipython Terminal Highlight HelloHelloHelloHelloHello	The string Hello is repeated 5 times after multiplying.
Show Slide Exercise 1	Pause the video. Try this exercise and then resume the video. Obtain the string as shown without typing out all the twenty hyphens.
[IPython Terminal] Type, s = "%% " + "-"*20 + "%%" print(s)	Switch to the terminal for solution. Type, s is equal to inside quotes two percentages plus inside quotes hyphen multiplied by twenty plus inside quotes two percentages Press Enter print inside parentheses s Press Enter
	Let's now look at accessing individual elements of strings. We can access individual elements in the string using the subscripts.
[IPython Terminal] Press Up arrow till we get a a[0]	Let us clear the terminal. Recall a. Press Enter. Type, a inside square brackets zero press Enter, gives us the first character of the string.
	The indexing starts from 0 and goes up to (n-1). where 'n' is the total number of characters in a string. We can access the strings from the end using negative indices.
[IPython Terminal] a[-1] a[-2]	a inside square brackets minus one gives us the last element of the string i.e. exclamation mark a inside square brackets minus two gives us the second element from the end of the string i.e. d
Show Slide Exercise 2 s = “Hello World” what is the output of s[-5] s[-10] s[-15] s[15]	Pause the video. Try this exercise and then resume the video. Given a string, s which is Hello World, what is the output of the following s[-5] s[-10] s[-15] s[15]
[Ipython Terminal] s = "Hello World” s[-5]	Switch to the terminal. Let us clear the terminal. Type s is equal to inside quotes Hello World press Enter s inside square brackets minus five gives W Similarly we will get e for s[-10].
[Ipython Terminal] s[-15]	s inside square brackets minus 15 gives us an IndexError. Since the string given to us is only 11 characters long.
[Ipython Terminal] s[15]	s inside square brackets 15 again gives IndexError for the same reason.
[Ipython Terminal] Press Up arrow till we get x x[0] = 'B'	Let us attempt to change one of the characters in a string. Let us clear the terminal. Recall x Press Enter Let us manipulate x. x inside square brackets zero equal to inside quotes B press Enter
Highlight the error	Why do we get an error? Initially the value of x[0] is ‘H’. Now we are trying to assign another value ‘B’ to x[0]. Recall, strings cannot be modified after it is created.
Show slide	We can split and join the strings by using the functions : split() and join()
Show slide Syntax for join() str.join(sequence)	To join a string, the syntax is str dot join inside parentheses sequence
[Ipython Terminal] s = “-” seq = ("a", "b", "c") print (s.join( seq ))	Switch to the terminal. Let us clear the terminal Type s is equal to inside quotes hyphen press Enter seq is equal to inside parentheses a comma b comma c press Enter print s dot join inside parentheses seq press Enter
Highlight output	We will get output as a hyphen b hyphen c It has joined a, b, c with hyphen.
Show slide syntax for split() str.split()	To split a string, syntax is str dot split open and close parentheses
[Ipython Terminal] str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( ))	Switch to the terminal Type as shown press Enter print str dot split open and close parentheses press Enter
Highlight output	We get the output like this. It has split the string at spaces.
Show Slide Summary slide	This brings us to the end of this tutorial. In this tutorial, we have learnt to, Define strings in different ways. Concatenate strings. Print a string repeatedly. Access individual elements of the string.
Show Slide Evaluation Write code to assign the string ’ is called the apostrophe, to a variable s How will you change s='hello' to s='Hello'. The variables s and t are string and r is integer. s=”Hello” t=”World” r=2 What is the output of s * r + t * r?	Here are some self assessment questions for you to solve Write code to assign the given string to variable s How will you change s is equal to hello' to s is equal to capital h Hello'. The variables s and t are strings and r is integer. They are assigned with the values as shown here, What is the output of s multiplied by r plus t multiplied by r?
Show Slide Solutions	And the answers, The given string can be assigned in this manner Strings cannot be manipulated after it is assigned a value The operation s multiplied by r plus t multiplied by r will print each of the two words twice as HelloHelloWorldWorld
Show Slide Forum	Please post your timed queries in this forum.
Show Slide Fossee Forum	Please post your general queries on Python in this forum.
Show Slide Textbook Companion	FOSSEE team coordinates the TBC project.
Show Slide Acknowledgment http://spoken-tutorial.org	Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India. For more details, visit this website.
Show Slide Thank You	This is Trupti Kini from IIT Bombay signing off. Thank you.

Contributors and Content Editors

Nancyvarkey, Nirmala Venkat, Trupti