Difference between revisions of "Python-3.4.3/C3/Getting-started-with-strings/English-timed"

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Latest revision as of 12:09, 31 May 2019

Tiime Narration
00:01 Hello Friends. Welcome to the tutorial on "Getting Started with Strings".
00:07 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.

00:24 To record this tutorial, I am using

Ubuntu Linux 16.04 operating system

Python 3.4.3 and IPython 5.1.0

00:39 To practise this tutorial, you should know how to

run basic Python commands on the ipython console

00:48 If not, see the pre-requisite Python tutorials on this website.
00:54 What are strings?

In Python, any character within a single/ double/ triple quotes is a string.

01:03 For example:

Single, double, and triple quotes can be used to denote a string as shown here.

01:13 Strings in triple quotes can be written in multiple lines.
01:19 We can also define empty strings. String is a collection of characters which cannot be modified after it is created.
01:30 Let us first open the Terminal by pressing Ctrl+Alt+T keys simultaneously. Type ipython3 and press Enter.
01:42 Let us initialise the pylab package.Type %pylab and press Enter.
01:51 Let us clear the terminal.

We can assign a string to a variable called a.

01:58 Type a is equal to inside any quotes Hello comma World exclamation mark and

Press Enter

02:09 Now let us learn string concatenation. Let us assign strings to variables.
02:16 Type

x is equal to inside quotes Hello

Press Enter

y is equal to inside quotes World

Press Enter

02:32 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

02:52 print inside parentheses z

Press Enter

Here x and y are string variables.

03:04 The addition operation performs the concatenation of two strings.
03:09 Here we can see the output of string concatenation.
03:14 Let us clear the terminal.

What if we multiply a string with an integer?

Let us find out!

03:23 Recall x string.

Press Enter

x multiplied by 5

Press Enter

03:33 The string Hello is repeated 5 times after multiplying.
03:39 Pause the video. Try this exercise and then resume the video.

Obtain the string as shown without typing out all the twenty hyphens.

03:51 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

04:14 print inside parentheses s Press Enter
04:20 Let's now look at accessing individual elements of strings. We can access individual elements in the string using the subscripts.
04:30 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.

04:47 The indexing starts from 0 and goes up to (n-1).

where n is the total number of characters in a string.

04:57 We can access the strings from the end using negative indices.
05:02 a inside square brackets minus one gives us the last element of the string i.e. exclamation mark
05:11 a inside square brackets minus two gives us the second element from the end of the string i.e. d
05:21 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
05:33 Switch to the terminal.
05:35 Let us clear the terminal.

Type

s is equal to inside quotes Hello World press Enter

05:46 s inside square brackets minus five gives W

Similarly we will get e for s[-10].

05:59 s inside square brackets minus 15 gives us an IndexError. Since the string given to us is only 11 characters long.
06:12 s inside square brackets 15 again gives IndexError for the same reason.
06:20 Let us attempt to change one of the characters in a string.

Let us clear the terminal.

Recall x

Press Enter

06:31 Let us manipulate x.

x inside square brackets zero equal to inside quotes B press Enter

06:44 Why do we get an error?

Initially the value of x[0] is ‘H’.

06:52 Now we are trying to assign another value ‘B’ to x[0]. Recall, strings cannot be modified after it is created.
07:02 We can split and join the strings by using the functions : split() and join()
07:08 To join a string, the syntax is str dot join inside parentheses sequence
07:17 Switch to the terminal.
07:19 Let us clear the terminal
07:22 Type s is equal to inside quotes hyphen press Enter seq is equal to inside parentheses a comma b comma c press Enter
07:41 print s dot join' inside parentheses seq press Enter
07:49 We will get output as a hyphen b hyphen c It has joined a, b, c with hyphen.
07:57 To split a string, syntax is str dot split open and close parentheses
08:05 Switch to the terminal

Type as shown press Enter print str dot split open and close parentheses press Enter

08:19 We get the output like this. It has split the strings at spaces.
08:25 This brings us to the end of this tutorial.
08:28 In this tutorial, we have learnt to,

Define strings in different ways.

Concatenate strings.

Print a string repeatedly and Access individual elements of the string.

08:42 Here are some self assessment questions for you to solve
08:46 1. Write code to assign the string ’ is called the apostrophe, to variable s

2. How will you change s is equal to hello to s is equal to capital H Hello.

09:01 3. The variables s and t are strings and r is integer.
09:07 They are assigned with the values as shown below, What is the output of s multiplied by r plus t multiplied by r?
09:17 And the answers,

The given string can be assigned in this manner

Strings cannot be manipulated after it is assigned a value

09:29 The operation s multiplied by r plus t multiplied by r will print each of the two words twice as HelloHelloWorldWorld
09:41 Please post your timed queries in this forum.
09:45 Please post your general queries on Python in this forum.
09:50 FOSSEE team coordinates the TBC project.
09:54 Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India. For more details, visit this website.
10:04 This is Trupti Kini from IIT Bombay signing off. Thank you.

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