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Friends, here our concept is

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'findall' and 'finditer' operations of 're' module.

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So let me explain this with a simple script.

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Let me open my editor.

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[no audio]

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So here let me import 're' module first.

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I have given some script name. Now

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let me take 'my_str' as suppose.

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[no audio]

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"This is python and we are having

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[no audio]

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python2 and python3 versions".

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[no audio]

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Now, let me take 'my_pat' as, so actually when you are going

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to take pattern based on your requirement. Suppose

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my requirement is I need to find out either 'python', or 'python2',

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or 'python3'. See how can I write? 'python',

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[no audio]

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So if you are strictly looking for 'python' word or 'python2'

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'python3' words, then you have to take '\b' then 'python'.

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So our requirement is 'python' or '2' or '3', that's why in

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square brackets just write '[23]', then your '?'.

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'?' means once or none. Then '\b'. That's it.

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Now it is going to represent three words - 'python', 'python2',

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and 'python3'. Among these three, right, if you go with suppose

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're.MATCH', you know what is the usage of 're.MATCH',

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so 're.MATCH(my_pat)',

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then your string.

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[no audio]

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See the result. What you are getting? You are getting 'None'.

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The reason is, 'match' will always look at very first in a given

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string for your given pattern.

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We don't have any 'python', or 'python2', or 'python3' at very

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first, that's why 'match' is not able to find that. Now if I

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go with the 'search', then you are going to get information

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about 'python' because the very first, anyway you know that,

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'search' is going to look for your given pattern in a given string

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from left to right. While going from left to right

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we have somewhere 'python',

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so among these three patterns - 'python', 'python2', and 'python3' here

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you've got, your 'search' got 'python'.

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That's why it is giving that. But my requirement is, I need

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to find all the matchings for your pattern which are there

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in a given string.

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[no audio]

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Right. So in a given string, 'python'

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is there, 'python2' is there, and 'python3' is also there.

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I want to find all these three.

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[no audio]

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Then our operations are, your 'findall' operations.

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Let me print with 're.findall' your pattern. Your pattern

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may represent one string or multiple strings, right, so that

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I am looking in a given string. Now see the result. You're

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getting all the matchings for your given pattern. Suppose

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if I take 'pyx'. Now, you don't have any matching for your

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pattern in a given string. You're getting a empty list. Be clear.

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'findall' will always give you a list.

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If there is a match it will give the list of values, if

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there is no match it

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will give empty list. Now by using 'findall' operation directly

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you can tell that how many matchings are there for your given

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pattern in a given string simply by applying a 'length' function

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on your 'findall'. See the result.

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If there is no matching directly it will give 0.

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[no audio]

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Because we know that for list we can apply 'length' function,

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and from that you can find out how many matches are there. That's it.

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So that is the use of your 'findall', or basically 'findall'

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is useful just to understand 'regex' operations.

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But if you go with your 'findall' we have a small drawback,

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of course directly we can able to find how many matches are

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there for a given, for your given pattern in a given string,

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but yeah, let me take this as 'python'.

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Yeah, now see that. But the disadvantage is it is not giving

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any information about your matching.

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I mean, what is the starting index of this matching,

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what is the ending index of this matching.

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So whenever if you want to look all the matchings in a given

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string for your given pattern, and if you want to see at the

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same time the starting index or ending index of your matching,

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then you have to go with the 'finditer' operation.

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Let me print first the information for your 'finditer',

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'my_pat,my_str'.

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First observe the output what you are getting.

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Let me comment your remaining 'print' statements.

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See the output. You are getting

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'callable_iterator object at', something, some information

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is there. Just observe that. Now I am writing 'py', some, let's

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say 'pyxthon'. Now, we don't have any matching for your

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given pattern because it is not 'python', 'pyxthon'. For this

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related word we don't have anything in our given string. Now if I look

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in this way, see the result what you are getting? Still you

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are getting some object.

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So first of all, 'finditer' will give always some object. Whether

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there is a match or not, whenever if you run 'finditer' it

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will give first some object. You need to remember this point.

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Then, see that I am using for loop for this. 'for each

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object in this pattern,

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I mean in this operation, let me print each object. Now, see the result.

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You're not getting anything, because first of all whenever

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if you run 'finditer' operation it will give some object

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whether there is a match or not secondary. If there is a match

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this loop will repeat. If there is no match you're not getting

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anything. Be clear.

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See in your 'match' and 'search' operation you are using 'if' condition.

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If your object is present then what is the match,

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what is the starting index,

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what is the ending index.

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But if you go with 'finditer' in order to use 'if' condition,

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because first of all 'finditer' for multiple matchings directly

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use for loop. If there is a match then loop will repeat. If

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there is at least one match your loop will repeat

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at least one time. If there are no matches then your loop,

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your loop won't repeat for at least one time.

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[no audio]

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Now see that. I am making now my pattern as 'p-y-t-h-o-n'. Now see

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the output. You're getting three objects.

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Suppose I am taking my pattern as only 'python2',

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be clear 'python2' or 'python3', now see the result.

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Your loop is repeating only one time and it is giving you

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object. Right.

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So be clear.

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Now, I have given my pattern as 'python', in square brackets '[23]',

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then '?'. Now see the result, three objects

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it is giving. So 'finditer' will consist of the number of

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objects based on how many matches are there for your pattern

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in a given string. And whenever if you use for loop for that

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iterator it will give the different objects for each

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match. Right. Now see that. Now I can directly write,

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what is the match.

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Let me write some message.

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[no audio]

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"The match is: ",

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[no audio]

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so here I will print the match.

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What is your match?

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'.group', right. See that.

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[no audio]

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See that. Then I want to find what is the starting index for

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each and every object.

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So "starting index",

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your 'each ob.start()', if you remember from your

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'match' and 'search' operation. Then what is the ending index.

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Be clear, ending index is nothing but your object,

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let me write it, your object, '.end() - 1'. Be clear.

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Don't forget about that. That's it.

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[no audio]

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Right. So guys, this is the usage of 'finditer'.

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So in most of the cases in your real time, you're going to

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work with 'search' and 'match' operations, but you have to know

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the functionality or working operation of your 'findall'

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and 'finditer' as well.

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Sometimes you may use, based on requirement you will use, but

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based on my experience

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I am telling that most of the cases we'll use 'search' and 'match'.

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[no audio]

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Okay. Okay guys,

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thank you for watching this video.

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[no audio]