Regular Expression Checker in Python

Key Takeaways

what is going on guys welcome back in this video today we're going to learn how to build a regular expression Checker in Python so let us get right into [Music] it all right so what we're going to do first is we're going to take a look at the final result as a motivational preview upfront also please excuse my voice today and occasional voice cracks I'm a bit cold so it might sound a little bit unusual today uh but this is what we're going to end up with a regex tool we have a text entry for regx a text entry for the text itself and we can find matches and we can check for a match so here I have prepared some text and I also prepared a regular expression and the idea is now that if I find matches it's going to highlight the matches for example here and here and when I type uh when I click on check match it's going to check if the whole text matches uh this rag X and if I remove all the stuff that does not match the rag X here if I just say uh check match it will tell me regx matches the whole text all right so let us get right into the implementation we're only going to use core python today we don't need to rely on any external packages and we're only going to have two Imports first of all import re e which is for the regular expression checking and then also import TK enter as TK for the graphical user interface and what we're going to do first is we're going to Define two functions the first one is going to be called FInd matches uh we're going to pass for now and we're going to have a second one which is going to be check match and we're going to pass here as well and then we're going to define the basic graphical user interface we're going to say root equals TK TK we're going to set a title which is going to be regex Checker or something like this uh and then we're going to add some basic UI elements that we saw in the preview so we're going to say here uh regor label is going to be tk. label and the label will have uh will be part of the root so it will have root as a parent element and the text is going to just be enter regex um without without a space here and then we're going to use a grid layout to place all of this into the root uh window so regex label. grit we're going to place this in row zero in column zero with a padding X of five and a padding y of five um and in the end of course we're going to do root main Loop so already we should have a graphical user interface with uh a simple label here now uh what we're going to do next is we're going to add the text entry so we're going to say regex uh entry is going to be equal to tk. entry it's going to be part of the root element and it's going to have a width of 50 and then we're going to use again the GD method to place this uh in the same row but not in the same column so still row zero column one um and the padding is going to be the same so padding X and padding y are going to be equal to five and then basically what we can do is we can copy this and we can slightly change this to be not regex label but text label and also text entry and what we want to do here is enter text and this of course will be Row one and this will be Row one and one more difference here is we're going to have a height of 10 here um is this correct oh actually this is a text not an entry so it looks like this now we have a text entry and we have a text area in addition to that now we're going to add two buttons the find button which is going to be a TK button which is going to be part of root we'll have the text FInd matches and will be linked to the function FInd matches from above which we have to still implement this one here um and then we're going to say find button. Grit the row is going to be equal to two the column is going to be equal to zero the column span is going to be equal to two so spans two columns uh petting X is going to be five pading Y is going to be five and we're going to make it sticky to West and East so sticky we then we're going to copy this we're going to paste this we're going to replace find by uh check and we're going to say check check match the command here is going to be check match and we're going to change this to row three and finally we want to have a result label which is going to be actually let me just copy this here this result label will have the text uh or actually in the beginning it won't have any text at all it will have a foreground which is going to be green by default and we're going to place this at Row 4 column zero column span equals 2 and that's it so this is our UI now and the only thing that we need to do now is we need to implement we need to implement the FInd matches and check match functions so for FInd matches it's actually not too complicated or actually both of them are not very complicated we basically just say that we want to have a regx object which is going to be equal to regx entry uh doget so it's going to be the content of this entry here it's just going to be the regular expression itself um and we also want to have the text and the text is basically the text entry doget but since this is now a text and not an entry field um we need to specify a starting point 1.0 and an end point and as an end we're going to use end minus one character minus one C to get rid of the last uh line break uh this is just how you select all the text and then we're going to say now uh if there is a regex and a text so if both are um if both are actually uh if both have some content what we do is we get all the matches by saying R find itter and we're going to pass here the regex and the text and what we do then actually we don't need this uh what we do then is we iterate over the matches for match in matches uh we say that the starting index of the respective match so you can have multiple matches but for this particular one the start index is the following 1.0 which is the starting location plus a certain number of uh characters we're going to make this an F string here and the certain number of characters will be match. start and we just add Char so this string basically says from the beginning where does the match start that many characters offset and the end index will be the same with match end uh and then we can say text entry tag at because now to this section we want to add a styling so we're going to say match will be added as a tag to start in index or from start index to end index and we're going to say now that the text entry tag config will be configured in a way that match has a certain styling and The Styling is that the foreground is going to be uh black and so basically the text is going to be black and the background is going to be red and the font is going to be whatever let's pick areial 10 and what did I pick B like this so that is basically defined matches function so this should already work if we go ahead and do the same thing again so we have this here and we have this here you can see that this already works now so the only function we need to implement is the check match function so what we're going to do here now is we're going to say again the regular expression is going to going to be whatever we get from the text entry or from the reix entry the text is going to be equal to text entry get from 1.0 until end minus one character and if regex and text are provided if it is a match the regex matches the text if that is the case all of the text um then we're going to say result label. config and I'm going to set the text equal to regx matches the whole text foreground is going to be equal to Green otherwise we're going to copy this regex does not match the whole text foreground equals R now we can do the same thing FInd matches Works check match says it's not a match now we can get rid of some stuff here and there you go matches old text so this is how you implement a regx checker with a graphical user interface in Python so that's it for today's video I hope you enjoyed it and hope you learned something if so let me know by hitting a like button and leaving a comment in the comment section down below also don't forget to subscribe to this Channel and hit the notification Bell to not a single future video for free other than that thank you much for watching see you in the next video and bye