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Hi, in this video will be filtering out file names, so for this example, I have this file folder

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in my working directory.

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So I invite you to create a similar folder named files.

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And inside that folder, please put these text files.

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You can find these files attached in the intellectual resources and upload them in your files directory.

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So let's suppose that these are bills pointing to different deeds or so, but the naming of these files

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is not that good.

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As you see, the personal name them did not use the best practices to name files, but that is why regular

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expressions exist.

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So our goal here is to filter only those bills from 1st of November on to the 20th of November.

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That means we want to extract this first file.

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Nov 13 The 2nd Nov 12 Nov 22 Not this one, because this is after November 20th, then we want to see

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this as well.

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November 14th.

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Not this, not October.

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So only the first one of the second and the third one.

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Let's see how we can do that before we write the regular expression.

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We want to get a list of these files.

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For that, we want to use.

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The path.

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Class of the past Liberal Library, if you don't know what this is, you need to go back to the calls

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and take the file and folder operations sections.

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There I introduce you to the path of the library.

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So then we want to create a root directory, which points to the folder where the files are located.

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So files is the name of the folder.

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Once we have that, we can create a list.

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File names, a single two routes do those eight to do.

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And let's print out financier converted into a list because it's a generator objects.

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That is the lease or file paths.

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There's a problem, though, these.

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Items are not strings.

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These are Paul 02:06 object types.

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So we want to convert them into strings.

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We can use a list comprehension for that.

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File names as a new variable SDR.

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So to denote that these items of this list will be strings that is equal to a list comprehension which

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would go like file name, dot name from each postfix path, we extracted the name, which will give

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us only that part for file name in file names.

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That's one.

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And let's print out file names, SDR now we're going to get on them to this here.

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That is because file names at this point of the execution is empty because a sense file names was a

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generator objects.

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That means when we converted into a list, when we converted the generator into a list that means we

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use the generators of the generator is exhausted.

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Therefore, a solution is to get to this list comprehension and also the variable called here and just

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place it in here.

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So now we generate a generator again in here and then we don't print it out, so we don't exhausted,

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but we use it in here in this list comprehension.

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This time we will get this list.

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So novelist, a story in this valuable and we can use it further.

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So let's now write for a regular expression.

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So we want to find some bills from November the 1st to November the 20th.

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That means our files will always have this no port, no some files will have a capital and so uppercase

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letter we can ignore case sensitivity using R e tort e kunwar keys as a second argument.

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So that means both north with a capital letter and north with lowercase letters will be included in

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the match.

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Sometimes, though, we have November and sometimes we have just north.

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So what we could do is we could just write a range here from A to Z and we could use a metal character.

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So zero or more times the asterisk.

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Like that.

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Then after that, we have a dash, right, so it could be no Dash or November dash.

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Then the next character could be one or two because we are filtering out only from the 1st of November

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until the 28th of November.

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So it could be no if one of two or three of four or five six seven eight nine, 10, 11, 12 and so

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on.

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So the next character is a number.

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And so we use these parentheses, so we have to use them or operators inside these like that.

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And we said the first number could be first from one to nine.

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So one, two nine range.

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So we want to work on every 10 digits whenever you want to feel two digits or numbers with regular expressions.

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So let's say one two six seven.

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You want to treat first the range from one to nine.

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So one digits, then you want to treat the next range from 10 to 19.

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Then the next.

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So that's what we're doing here.

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First, we work on the first range of numbers, so one digits from one to nine.

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We see that or it could be 10, 11, 12 until 19.

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So it could be one, followed by zero to nine.

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So one zero one one one two one three one four and two one nine.

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Then again, the vertical bar, or 20.

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So just to see if you had to go up to 23rd of November, then you do something like two of them in square

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brackets, you'd insert the range zero to three.

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So that would include 20, 21, 22 and 23.

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This is not the case.

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We just want 20.

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So 20 is fine.

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Then after that, after the number, we have four dots and the tricky part.

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So I executed that, but we haven't extracted the actual matches yet, so I shouldn't have executed

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it.

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So let's add the matches.

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Matches are.

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Hmm.

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Now we have a list here, so be careful because previously we were working on text strings, but this

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is at least steroids of your of.

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The IP addresses were coming as Texas wants single string.

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So in this case, we want to work on a list comprehension.

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We would see something like file name for file name in file names, a city or so we go through that

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list.

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But if pattern that finds full file name.

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Matches, I'll explain you, that's a list comprehension in just a bit.

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So that's the ultimate Nov 12, Nov 13 November 14th.

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No, there's not 20 here.

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So let's try to add a 20 in here in these files.

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So create a new file and let's say, Nov 20, the 16.

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Go back to the notebook and executed the first cell where we get the files from the Working Directorate

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execute that.

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So you've seen enough 20s there now, execute the other sell as well, and we get enough 20, so it's

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working well.

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But let me explain you how this works.

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So we are iterating over the file names.

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Trim lists this list here.

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File name for file name in five-string and now we will includes in the matches list only if this evaluates

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to true.

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So this evaluates to true only when the pattern is formed in the file name in the current file name

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of the iteration.

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So we iterate over these.

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So let's say first, we have this as the file name variable inside this list comprehension and we see

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is this pattern in that file name.

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So if it is, then that's file name will be included in the list, so it will be added to the matches

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list.

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Otherwise, it will not be added to that list.

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So we will end up with a matches list, which will contain only those file names which.

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Satisfy this condition here, and that concludes this video on filtering data that contain numbers,

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so thank you again, and I'll talk to you in the following videos.