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So far in this section we took the boats were regular expressions in the first video, then in the second

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video, we looked at an example of a regular expression.

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This one in here, we extracted the email addresses from this text.

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In this video, we will take a look at the meter characters that you can use to build regular expressions.

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And I'm going to go through each of these characters and explain them using the same example.

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So you are familiar with this text now.

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That's a sort of text variable, and that is the codes.

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So we will be changing the regular expression here, the pattern using all these metal characters.

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Well, let's start with the first one.

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The first one is the dot, a dot is a major character.

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You can also call these special characters so metal characters.

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These dot means you want to match any possible characters.

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It could be a wide space, a comma, a laser lowercase or uppercase, and any other character.

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Even the dots can be matched using these dots character.

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So well, let's take a look at the example here.

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We did use these dots, actually.

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You see here what these did, in fact, is it matched any character at this position.

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So we had any character, but space, that's then we had it here than we had any character again, except

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space.

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Then we had any character.

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So one single dot means any character.

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So it happens to be in our scenario that this any character was a dot.

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But even if it is, for example, an equal operator, let's say, and we execute this cell again, we're

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going to match both these email addresses because the DOT captures any character.

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So you see that it's just so you see that it also matched this equal operator.

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But in our example, we actually have dots in email addresses, and that brings us to the second major

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character.

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This character is used to escape one of the major characters.

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So to treat it as a regular character, which means if you put that backslash before a major character,

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the dots in this case, and if this first e-mail address has, that's equal operator as a character

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instead of the dots and you execute this, we're only going to get to the second email address because

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in this pattern, this time the dots is a literal dots.

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It's a normal character because it has this escape made-up character in front.

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So that's backslash comes in handy whenever you want to escape a major character.

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Next, the square brackets, which could have anything inside.

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So these three dots are just to denote that the square brackets come with something inside.

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So this is an example of the square brackets.

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That's metal character, and that's it's another example.

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So inside these square brackets, we can put a single character or arrange or characters within those

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brackets.

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Let's see what happens if we remove this character here and the space and inside the first pair of brackets

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we inputs, another executes.

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We get the second email address, so another and then we have ETS and so on.

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But what if we remove the brackets like that and we execute again, we get the same results?

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So what is the point of having those brackets when you get the same output?

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Well, when you have the brackets, you can have the characters arranged in any order.

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So let's change the place of a and put it off the end.

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So in a other instead of another, if you execute that, it's still going to match that string.

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So the order of characters, it doesn't matter if all these characters match a string, regardless of

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the order, you will have a match.

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But if you remove the brackets, no.

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You will not get to the scene because this is not a major character.

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No, it's not inside those square brackets.

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So let's put the brackets again.

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Of course, if you remove an order and you execute Steve, you don't get a match because not all the

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characters are matched.

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That's what I'm trying to explain here that the order does not matter.

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Next, the gloss metal character, we already use the glass.

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It means that, you know, we had this.

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It means match any known space character one or more times.

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So that means this first part or the email address codes have at least one or more known space characters,

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which could be letters on the scores, dashes, columns, semicolons, et cetera, but not spaces.

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Next, we have a question mark.

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This matches the preceding element zero, actually, it should be zero or one time.

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So see what happens if we replace the plus here with a question mark and executes.

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You will get only the last letter of the words another because one matches is the best.

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That's this question mark and two.

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So it's only catch catches one letter.

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Then we have the asterisk, which matches the preceding elements zero or more times.

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So the Plus got at least one or more times, which means in the case of class, which was like this.

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We got another example, the.

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And if we have adults here, in example dot com, we also get that.

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But if we replace that to an asterisk and execute again, we get the same result.

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But see if we at dot com to this, it's blah blah blah.

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We will get at blog dot com.

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Also, because the asterisk matches zero or more elements, which means there are zero elements before

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the ETS.

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So zero elements are allowed to be before the at symbol.

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Therefore, we get that.

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So if you don't want that, you want to use the loss to get at least one element if you want a particular

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number of elements to match a particular number of characters.

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So not one or more, not zero or more, but let's say three, in that case, you use that and the number

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of characters you want to match.

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So let's say three and you gets that p l e.

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So we're looking at this expression.

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I jumped over this because it has to be that, so I'm going to replace it.

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It's a place that's in there and you can also do it like this.

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So match from three to six, for example, without the space, sorry.

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And so you get that.

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So this is not what we want in this case.

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So Call US Again is the metal character that extracts all the emails.

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Next, we have this symbol, which matches the beginning of a line of a beginning of a string or a line.

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Is this this high here?

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That's a beginning of a of silver string.

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That means if we add that so here, for instance, we're not going to get anything because we are telling

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Python to get all sorts of email addresses that are met the first place and the first position of the

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string.

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So it's not really what we need in this place.

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You could be using this in in special scenarios, but not in this example.

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Same goes for the end of the string, so this will match only the email addresses of the end of the

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string.

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Again, it's not what we need this one here.

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We use that already, so it is this one.

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So it matches a single character or a range that is not contained within the brackets.

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So the space is contained within the brackets.

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So the space is not matched, but everything else.

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So that is not contained within those brackets is matched.

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So on the dashes, letters, etc. OK.

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This seemingly long expression here is an owner operator.

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Let's see how we would be using this.

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Let's suppose that we only want to extract the email addresses that have dot com or dot to eat.

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So if we had something else here, such as another example that and E and we don't want to extroverts

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email address this regular expression would not work anymore because it gets us all the email addresses

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to exclude that you want to be most more specific here instead of seeing A to Z.

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You delete that.

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And so you use parentheses which are explained later on.

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In here and inside parentheses, you see question mark a column and then you see on the vertical bar

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d e.

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Execute that, and you get only those that have come or the eat at the end of email address.

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So that is the expression for that.

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So that brings us to the last major character which matches an optional expression.

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So this is used usually in conjunction with an owner operator, as you saw in this case.

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So that is a list of metal characters.

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It's hard to remember them immediately.

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So you gets better as you use them in more examples, but it's a good idea to keep this list in a place

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so you can refer to that as you need it.

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So now we're done with this example.

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We will be looking at some of examples now so that you get more practice with regular expressions.

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So I'll see you in the next few.