Python-3.4.3/C3/Manipulating-strings/English-timed

Time	Narration
00:01	Welcome to the spoken tutorial on Manipulating Strings.
00:06	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
00:27	To record this tutorial, I am using Ubuntu Linux 16.04 operating system Python 3.4.3 and IPython 5.1.0
00:43	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.
00:59	First let us see about string slicing.
01:03	String slicing allows us to obtain substrings.
01:08	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
01:24	Let us start ipython. Open the terminal.
01:29	Type ipython3 and press Enter. From here onwards, remember to press the Enter key after typing every command on the terminal.
01:40	Let us understand the string slicing with an example. Type, data is equal to inside double quotes python
01:51	Type, print inside brackets data inside square brackets 0 colon 3
01:59	We get the sliced substring as pyt.
02:03	Note that, we are slicing the string from the index 0 to 3.
02:09	By doing so, the string elements from index 3 are not included.
02:15	Let us create a list, week underscore name which has names of the days of the week.
02:21	Type as shown. Type, s is equal to inside double quotes saturday
02:31	We need to check if the first three characters of the given string exists in the list week underscore name.
02:39	Strings can be sliced into substrings.
02:43	To get the first three characters of the string s, type, s inside square brackets 0 colon 3
02:52	As you can see, the character at last index ie 3 is not included in the sliced output.
03:00	We will check if the substring of s is present in the list week underscore name.
03:06	Type s inside square brackets 0 colon 3 in week underscore name
03:14	We get the output as True which indicates that the substring is present in the list.
03:20	Pause the video. Try this exercise and then resume the video.
03:26	Obtain the substring excluding the first and last characters from the string s.
03:32	Switch back to terminal for the solution.
03:36	Type, s inside square brackets 1 colon -1
03:42	As we already know, the last element of the string can be accessed using the index -1.
03:49	Next let us learn to check if a given string is a palindrome or not.
03:55	A palindromic string is a string that is same as its reverse.
04:01	Type, s1 is equal to inside double quotes dad
04:07	Now, we need to compare this string with its reverse.
04:11	For reversing s1, we stride the string from the first to last character.
04:17	It is done by keeping the start and stop values as empty and step as -1.
04:24	That is s1 inside square brackets colon colon -1
04:30	Now, we will check if the string s1 is a palindrome or not.
04:35	Type, s1 is double equal to s1 inside square brackets colon colon -1
04:44	The output True indicates that it is a palindrome.
04:49	If the given string has capital D in dad instead of small d, the comparison would return False.
04:57	So, we have to convert the string to all lowercase or uppercase, before comparison.
05:04	Python provides the string methods lower and upper to achieve this.
05:10	Let's try it out. Type, s2 is equal to inside double quotes capital D ad
05:19	Type s2.upper open and close parentheses We get all the characters in uppercase.
05:29	Type s2 As you can see, s2 has not changed.
05:36	It is because, method upper returns a new string. It doesn't change the original string.
05:43	Let us compare the original and reversed string in lowercase. Type as shown. As expected the output is True.
05:56	Pause the video. Try this exercise and then resume the video.
06:02	Check if each element in the following list is present in the list week underscore name.
06:09	Switch back to terminal for the solution.
06:13	Type as shown. It returns False for python as it is not there in the list week underscore name.
06:24	Next let us learn to use replace method.
06:28	Type, email is equal to inside double quotes info[at]fossee[dot]in
06:36	We often encounter email addresses which have @ symbol and periods replaced with text as shown.
06:44	Let us learn how to get back proper email addresses.
06:49	Now, we will first replace the [at] with the @ symbol, using the replace method.
06:55	Type as shown. You can see that the @ symbol is properly replaced now.
07:05	Pause the video. Try this exercise and then resume the video.
07:11	Replace the [dot] with '.' symbol in the given email.
07:16	Switch back to terminal for the solution.
07:20	Type as shown.
07:24	Now the variable email underscore proper has the email in the proper form.
07:30	Next, we will look at another interesting problem.
07:34	Let us say, we have a list of email addresses in the variable email underscore list as shown.
07:41	We will obtain one long string of email addresses, separated by commas or semicolons.
07:48	We will use the string method join for joining the list items into a single string.
07:55	Type as shown. Comma followed by a space will give the string with the same formatting.
08:04	Type, print inside parentheses email underscore str You can see that all the email addresses joined into a single string.
08:16	Pause the video. Try this exercise and then resume the video.
08:22	From the email underscore str, change the separator to semicolon instead of comma.
08:29	Switch back to terminal for the solution.
08:33	Type as shown. We see that the email addresses are joined by a semicolon followed by a space.
08:43	This brings us to the end of this tutorial. Let us summarize.
08:49	In this tutorial, we have learnt to, Obtain substrings Reverse strings by using the index numbers
08:58	Use the following methods upper() lower() replace() and join()
09:05	Here are some self assessment questions for you to solve 1. Given a string s = "this was a string”, how will you change it to "this wasn't a list"? 2. The string s is assigned as shown, change the string to "friends"
09:25	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.
09:39	2. In order to remove dots and to get substring we stride the string s.
09:45	To change the string to lowercase, we use the string method lower().
09:51	Please post your timed queries in this forum.
09:55	Please post your general queries on Python in this forum.
10:00	FOSSEE team coordinates the TBC project. (16.45)
10:04	Spoken Tutorial Project is funded by NMEICT, MHRD, Govt. of India. For more details, visit this website.
10:14	This is Priya from IIT Bombay signing off. Thanks for joining.

Contributors and Content Editors

Pratik kamble