Python-3.4.3/C3/Manipulating-strings/English

Visual Cue	Narration
Show Slide: Title	Welcome to the spoken tutorial on Manipulating Strings.
Show Slide Objectives	In this tutorial, we will learn to Slice a string and get substrings out of them Reverse a string Replace characters in a string Convert a string to upper or lowercase and Join list elements to form a 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-requisite	To practise this tutorial, you should know how to use basic datatypes, operators, strings and lists If not, see the relevant Python tutorials on this website.
Show Slide string slicing	First let us see about string slicing. String slicing allows us to obtain substrings. The syntax for the string slicing is: string_name inside square brackets start colon stop or string_name inside square brackets start colon stop colon step
Open the terminal	Let us start ipython. Open the terminal.
Type ipython3 Press Enter	Type ipython3 and press Enter. From here onwards, remember to press the Enter key after typing every command on the terminal.
Type, data = “python”	Let us understand the string slicing with an example. Type, data is equal to inside double quotes python
Type, print (data[0:3]) Highlight the output pyt	Type, print inside brackets data inside square brackets 0 colon 3 We get the sliced substring as pyt. Note that, we are slicing the string from the index 0 to 3. By doing so, the string elements from index 3 are not included. <<PAUSE>>
Type, week_name = ["sun", "mon", "tue", "wed", "thu", "fri", "sat"]	Let us create a list, week underscore name which has names of the days of the week. Type as shown.
Type, s = "saturday" Highlight ‘sat’	Type, s is equal to inside double quotes saturday We need to check if the first three characters of the given string exists in the list week_name.
Type, s[0:3] Highlight the output	Strings can be sliced into substrings. To get the first three characters of the string s, type, s inside square brackets 0 colon 3 As you can see, the character at last index ie 3 is not included in the sliced output.
Type, s[0:3] in week_name Highlight True	We will check if the substring of s is present in the list week underscore name. Type s inside square brackets 0 colon 3 in week underscore name We get the output as True which indicates that the substring is present in the list.
	Pause the video. Try this exercise and then resume the video.
Show Slide Assignment 1	Obtain the substring excluding the first and last characters from the string s.
Switch to terminal	Switch back to terminal for the solution.
s[1:-1] Highlight -1	Type, s inside square brackets 1 colon -1 As we already know, the last element of the string can be accessed using the index -1. <<PAUSE>>
Type, s1 = "dad"	Next let us learn to check if a given string is a palindrome or not. A palindromic string is a string that is same as its reverse. Type, s1 is equal to inside double quotes dad
Textbox s1[::-1]	Now, we need to compare this string with its reverse. For reversing s1, we stride the string from the first to last character. It is done by keeping the start and stop values as empty and step as -1. That is s1 inside square brackets colon colon -1
Type, s1 == s1[::-1] Highlight the output	Now, we will check if the string s1 is a palindrome or not. Type, s1 is double equal to s1 inside square brackets colon colon -1 The output True indicates that it is a palindrome.
Textbox "Dad"	If the given string has capital D in dad instead of small d, the comparison would return False. So, we have to convert the string to all lowercase or uppercase, before comparison.
Type, s2 = "Dad"	Python provides the string methods lower and upper to achieve this. Let's try it out. Type, s2 is equal to inside double quotes capital D ad
Type, s2.upper()	Type s2.upper open and close parentheses We get all the characters in uppercase.
Type, s2 Highlight the output	Type s2 As you can see, s2 has not changed. It is because, method upper returns a new string. It doesn't change the original string.
Type, s2.lower() == s2.lower()[::-1] Highlight the output	Let us compare the original and reversed string in lowercase. Type as shown. As expected the output is True.
	Pause the video. Try this exercise and then resume the video.
Show Slide Assignment 2 ['SATURDAY', 'python', 'Sunday']	Check if each element in the following list is present in the list week_name.
Switch to terminal	Switch back to terminal for the solution.
Type, for day in ['SATURDAY', 'python', 'Sunday']:print (day, day.lower()[:3] in week_name) Highlight python False	Type as shown. It returns False for python as it is not there in the list week_name.
Type, email = "info[at]fossee[dot]in" Highlight at and dot	Next let us learn to use replace method. Type, email is equal to inside double quotes info[at]fossee[dot]in We often encounter email addresses which have @ symbol and periods replaced with text as shown. Let us learn how to get back proper email addresses.
Type, email_at = email.replace("[at]", "@") print (email_at)	Now, we will first replace the [at] with the @ symbol, using the replace method. Type as shown. You can see that the @ symbol is properly replaced now.
	Pause the video. Try this exercise and then resume the video.
Show Slide Assignment 3 info@fossee[dot]in	Replace the [dot] with '.' symbol in the given email.
Switch to terminal	Switch back to terminal for the solution.
Type, email_proper = email_at.replace("[dot]", ".") print (email_proper)	Type as shown. Now the variable email_proper has the email in the proper form. <<PAUSE>>
Type, email_list = ["info@fossee.in", "enquiries@fossee.in", "help@fossee.in"]	Next, we will look at another interesting problem. Let us say, we have a list of email addresses in the variable email_list as shown. We will obtain one long string of email addresses, separated by commas or semicolons.
Type, email_str = ", ".join(email_list)	We will use the string method join for joining the list items into a single string. Type as shown. Comma followed by a space will give the string with the same formatting.
Type, print (email_str) Highlight the output	Type, print inside parentheses email_str You can see that all the email addresses joined into a single string.
	Pause the video. Try this exercise and then resume the video.
Show Slide Assignment 4	From the email_str, change the separator to semicolon instead of comma.
Switch to terminal	Switch back to terminal for the solution.
Type, email_str = email_str.replace(",", ";") print (email_str) Highlight the output	Type as shown. We see that the email addresses are joined by a semicolon followed by a space. <<PAUSE>>
Show Slide Summary	This brings us to the end of this tutorial. Let us summarize. In this tutorial, we have learnt to, Obtain substrings Reverse strings by using the index numbers Use the following methods upper() lower() replace() and join()
Show Slide Self assessment questions s = "this was a string"	Here are some self assessment questions for you to solve Given a string s = "this was a string”, how will you change it to "this wasn't a list"? The string s is assigned as shown, change the string to "friends"
Show Slide Solutions of self assessment questions s = s.replace("string", "list") s = s.replace("was", "wasn't") print(s)	And the answers, 1. We will use the replace method to accomplish this. Here string and was in the statement will be replaced by list and wasn't respectively.
Show Slide Solution of self assessment questions s[::2].lower()	2. In order to remove dots and to get substring we stride the string s.To change the string to lowercase, we use the string method lower().
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.
Slide Textbook Companion	FOSSEE team coordinates the TBC project. (16.45)
Show Slide Acknowledgment http://spoken-tutorial.org	Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India. For more details, visit this website.
Previous slide	This is Priya from IIT Bombay signing off. Thanks for joining.

Contributors and Content Editors

Nancyvarkey, Nirmala Venkat, Priyacst