Python for Absolute Beginners Transcripts
Chapter: Using external Python packages
Lecture: Managing requirements with the requirements.txt file
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0:00
Now that we've got our virtual environment here
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we're ready to use colorama
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there's still one more step that we should take.
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There's nothing requiring us to take this at the moment
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but in the future you're going to
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be really glad that you did.
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So, one of the things that's important is for us
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to express to other automated systems
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other developers or users who get this code
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and want to run it, that this code now is going
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to require colorama.
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If we don't have colorama installed and we run it
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what's going to happen?
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It's going to crash and say we don't know what colorama means.
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So in order for us to make that clear
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like this program must have colorama
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or whatever other external package is installed
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there's a convention that all the tooling understands.
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Come over here and add a new blank file
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called requirements.txt.
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And down here all we have to do is put
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the same command we would type to pip install whatever
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into this file we just put the whatever.
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So in this case we just put colorama.
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Notice that PyCharm is saying there's a thing we need you
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to install called Colouram, well no that's not true
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and once we put colorama it's good.
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This squiggly, just PyCharm thinks it's misspelled
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which is weird, but if we also depended upon requests
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we could have it like that
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and if we click this button it's the same as if
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we went and activated the virtual environment
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and said pip install request
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but we're not actually going to do that here.
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Let's go and just see how we might add another library
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that we're not going to use yet
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but we're going to use eventually this thing
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called prompt_toolkit.
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Now if we go down here to the terminal
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it should have the virtual environment activated.
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You can double check by saying which or where Python
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and it's going to be the one in that folder, if it's right.
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So if we come down here and say pip list
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you can see here's colorama, but not prompt_toolkit.
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Also if you go to this UI bit here's colorama
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but not prompt_toolkit.
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All we do is click this, PyCharm knows, hey
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I told you the tooling understands requirements.txt
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it knows that this means something
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if we click it, it's going to go and say
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hey that got installed okay.
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If we go back to the UI
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look here now prompt_toolkit is installed
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similarly if we look at it this way
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we say pip list, we now have prompt_toolkit.
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We're not using that yet
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but those are the two we're going to need
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so I put them into our requirements file, right here.
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That's cool, right?
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So we've got this requirements file
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that any time you get this code out and you want to run it
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you just can say actually there's a way
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to say install everything I need from here
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as well as pip install dash R, or our requirements file
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requirements.txt and it tries to install all the things.
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We saw that's basically what PyCharm did
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it looked and said there's some stuff that's missing
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click this button and I'll run that command for you.
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That's the requirements.txt and you should always have one
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any time you're using an external package.
