Using and Mastering Cookiecutter Transcripts
Chapter: Creating Cookiecutter templates
Lecture: Demo: post-generation hooks
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0:01
It's time to work on the final finish product by creating a post generation hook.
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So these are very useful, and one of the key reasons we might create
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a post generation hook would be to display instructions about getting started.
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So once your project is created, you might want to say hey user,
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thanks for creating my project, here is the next steps you have to take
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maybe you have to pip install the requirements,
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or you've got to setup your system this way, or bunches of things.
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So we can so a little nice message right at the end by using a post generation hook.
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One of the things that is very common in these templates,
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but is not built in to Cookiecutter at the time of this recording,
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is the ability to include or exclude files and directories conditionally.
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So, we can write a little bit of code to do that, and I've changed our project,
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just a tiny bit to set this up before us, so over here notice there is this folder
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called color_files and it has a blue_file a green_file and a yellow_file.
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If we look at the cookiecutter.json, I trimmed this down just for sanity sake,
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so we have blue, green and yellow,
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these three you can all create projects of that type,
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remember our pre generation hook already will not allow you
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to create a black one, because we were just playing around with that idea.
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So we have these three realistic options for a color.
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Now, when you choose a color, what we want to do is only include the blue_file,
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which simply says this is the file that appears only in blue projects,
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when you choose blue. If you choose green, we want to have only green,
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we want to get rid of blue and yellow, if you choose green. Okay.
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We could take this in a much more advanced direction but I think if you see this,
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this will be enough for you to sort of bring this concept of conditionally
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including files, directories and various things in your own projects.
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So, how do we do that, we don't need any of these, let's work on this file one first,
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and then we'll come back with the instructions second.
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So, let's go here and let's go and set this up to have this main convention here
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we'll go up here, we'll write at the top, I like to put this right at the top,
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have the function that orchestrates what we're going to do.
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So the first thing we're going to do is we're going to remove unused project files,
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let's say, so that is going to go here and then we are also going to display
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getting started instructions, so we're going to fill that out here in a minute.
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Okay, so how are we going to remove our files,
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let's try one more little helper function called delete_files,
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this will be file_list, and this will be a working_dir.
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Okay so we're going to need to use an os module in Python,
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so we are going to import os and let's just go down here and say
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for file in file_list: full_file = os.path.join(working_dir, file) we want to take the working directory
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and in a platform independent way combine it with this file.
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So this is going to be the file and then we're going to test whether it exists,
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so we'll say if os.path.exists(full_file):, we're going to say os.remove(full_file).
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So, we were given a set of files and if they exist, we want to delete them
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so up here we are going to choose which ones do we send to this function,
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which ones do we actually want to delete based on some sort of input.
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Let's go ahead and also here say else:
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print("WARNING: Could not find file to remove in hook: " + full_file)
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And we'll just print out the full file here. Hopefully, if we do things right,
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we'll never ever see that warning, but just in case.
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Now what we need to do is figure out the favorite_color.
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And as long as we spell this correctly, this will be cookiecutter.that
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Like so, alright, so that is going to be the color,
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and then we just need to test is it blue, green or yellow,
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and first of all, let's get the working directory that is going to be the same,
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so we'll say os.path.abspath(os.path.curdir)
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So, when our hook executes, it's going to execute in the context
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in the current directory, it's going to be where that template is,
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where the files were created, okay.
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Then we'll say like this, file_list = [] (is empty), we'll say if favorite_color == 'yellow'
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say file_list is going to be and we'll just put "blue_file.txt" and "yellow_file.txt"
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Sorry green_file, okay, we got "blue_file.txt" and "green_file.txt",
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now there is a bit of a problem in that,
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this current directory here is actually this directory,
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and we need to get into the colors file, so we could do one more step,
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if we know we're only working in the colors file folder, we'll just do like this.
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Join that directory, with color files.
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And then we can just say the short names here.
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And let's just keep going, and finally in all of these we just say delete_files(),
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we give it the file_list and the working_dir.
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Okay, if everything is working correctly,
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we should be able to delete these files,
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okay, now what we're going to do is we want to create a few projects
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and we should see if we choose blue, we'll only have that left, if we choose yellow,
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we'll only have this, and so on.
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Alright, let's go give this a shot.
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So we're going to run cookiecutter cookiecutter-colors I am in the directory
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that has the template that is why I can say it this way, it says my project,
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this will be green project, green project is good,
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this is going to be Michael, that's fine,
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let's pick green, alright, let's see what happens.
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Boom okay, so now we have the green project, so let's see what's in there,
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color_files, ta-da, we have only the green one, beautiful.
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Alright, let's try this again and this time let's do it with yellow.
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So yellow project, yellow project like this, on this date,
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make sure we pick yellow, and we'll say open yellow and this time,
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we got the color_files, here, yellow,
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okay, and so that is how this works,
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we created a post generation hook and all of these files here
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were copied over in the project creation,
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and if we had Jinja expressions in them,
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they would have been expanded and filled out
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and possibly conditionally done and so on.
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Then, after all that was done, we said okay,
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well probably some extra files were copied,
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like blue_files were copied, even in the yellow projects,
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we're just going to go and do a little bit of code here to clean them up, right,
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figure out what they choose and then
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write just a tiny bit of code to go and delete them
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and hey, how about that, we didn't mess up and see this warning. That's cool.
