Python-3.4.3/C2/Getting-started-with-strings/English
Visual Cue | Narration |
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containing title, name of the production team along with the logo of MHRD |
Hello Friends. Welcome to the tutorial on "Getting Started with Strings". |
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Objectives
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At the end of this tutorial, you will learn to,
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System Specifications |
To record this tutorial, I am using * Ubuntu Linux 16.04 operating system
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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. |
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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.
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Strings in triple quotes can be written in multiple lines.
That is, string cannot be modified after it is created.
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[Terminal]
ipython3
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Let us first open the Terminal by pressing Ctrl+Alt+T keys simultaneously.
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[IPython console]
%pylab and press Enter. |
Let us initialise the pylab package.
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[IPython Terminal]
a = 'Hello, World!' |
We can assign a string to a variable called a.
Type a is equal to inside any quotes Hello comma World exclamation mark Press Enter |
[IPython Terminal]
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Now let us learn string concatenation.
Let us assign strings to variables. |
x = 'Hello'
y = 'World' z = x + ', ' + y + '!' print(z) |
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x is equal to inside quotes Hello Press Enter y is equal to inside quotes World Press Enter Now, let us add the two strings.
Press Enter print inside parentheses z Press Enter Here x and y are string variables.
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Highlight + | The addition operation performs the concatenation of two strings. |
Highlight the output | Here we can see the output of string concatenation. |
[IPython Terminal]
Press Up arrow till we get x
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What if we multiply a string with an integer?
Let us find out! Type Recall x string. Press Enter x multiplied by 5 Press Enter |
Show Ipython Terminal
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The string Hello is repeated 5 times after multiplying. |
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Pause the video. Try this exercise and then resume the video.
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[IPython Terminal]
print(s) |
Switch to terminal for solution.
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.
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[IPython Terminal] Press Up arrow till we get a a[0]
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Recall a.
Type, a inside square brackets zero gives us the first character of the string.
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[IPython Terminal]
a[-2] |
a inside square brackets minus one gives us the last element of the string i.e. !
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Show Slide Exercise 2 s = “Hello World” what is the output of s[-5] s[-10] s[-15] s[15]
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Pause the video. Try this exercise and then resume the video.
s[-5] s[-10] s[-15] s[15] |
[Ipython Terminal]
s = "Hello World” s[-5] |
Switch to the terminal.
Type s is equal to inside quotes Hello World press Enter s inside square brackets minus five gives us 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'
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Let us attempt to change one of the characters in a string.
Type, Recall x Let us manipulate x. x inside square brackets zero equal to inside quotes B press Enter
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.
We are getting added anan error because, strings are immutable and so cannot be manipulated.
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Show slide | We can split and join the strings by using the functions :
split() and join()
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Syntax for join() str.join(sequence) |
To join a string str dot join inside parentheses sequence |
[Ipython Terminal]
s = “-”seq = ("a", "b", "c"); print (s.join( seq ))
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Switch to the terminal.
Type s is equal to inside quotes hyphen press Enterseq is equal to inside parentheses a,b,c press Enter print s dot join inside parentheses seq press Enter |
Highlight output | We will get output as a-b-c
It has joined a, b, c with hyphen. |
Show slide syntax for split()
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To split a string
str dot split open and close parentheses |
[Ipython Terminal]
str = "Line1-abcdef \nLine2-abc \nLine4-abcd";print (str.split( ))
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str is equal to "Line1-abcdef \nLine2-abc \nLine4-abcd" press Enterprint str dot split open and close parentheses press Enter |
Highlight output | We get the output ['Line1-abcdef', 'Line2-abc', 'Line4-abcd']
It has split the string at spaces. |
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Summary slide
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This brings us to the end of this tutorial. In this tutorial, we have learnt to,
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Evaluation # Write code to assign the string ' is called the apostrophe , to a variable s
s=”Hello” t=”World” r=2
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Here are some self assessment questions for you to solve
Write code to assign the string ' is called the apostrophe , to variable s
They are assigned with the values as shown below: s=”Hello” t=”World” r=2
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Solutions
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And the answers, # The given string can be assigned in this manner
s = " ` is called the apostrophe" 2.Strings cannot be manipulated after it is assigned a value.
two words twice as HelloHelloWorldWorld
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Forum |
Please post your timed queries in this forum. |
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Fossee Forum |
Please post your general queries on Python in this forum. |
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Textbook Companion |
FOSSEE team coordinates the TBC project. |
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Acknowledgment |
Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India.
For more details, visit this website. |
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Thank You |
This is _________ from IIT Bombay signing off.
Thank you. |