Managing Python Dependencies Transcripts
Chapter: Managing Third-Party Dependencies With pip
Lecture: Introduction to Dependency Management
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You might have heard the term dependency management
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in combination with Python packaging.
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What is dependency management, and what do you need it for?
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So most real world programs that you are going to write
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and that you are going to encounter are likely to use
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third party libraries and frameworks.
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These frameworks that the program uses and that the program requires
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to function are called dependencies, so here is an example.
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Let's say you are working on a project called "my program" and to do its job,
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my program actually relies on two other packages,
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and so my program would enlist these other dependencies
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and use those other packages and other libraries to get the job done.
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So maybe you don't want to reimplement some function like HTTP downloads
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and you program would just use that in a library
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and these packages "super library" and "other dependency",
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they would be called dependencies of my program in this case.
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Of course, not only can your programs have dependencies,
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but the dependencies of you programs can have dependencies again,
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and so on, and this is what we refer to as transitive dependencies,
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or you could also think of them as dependencies of dependencies
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or secondary dependencies.
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So let's take a look at our "my program" example.
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So in this case, we said "my program" has two direct dependencies
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and that will be "super library" and "other dependency",
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now what you can see here is that "super library" and "other dependency" itself,
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actually have dependencies again,
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and some of the dependencies of those dependencies, have dependencies again.
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So this is a whole tree of dependencies.
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On the one hand, having this flexibility is great
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because it allows us to abstract away all kinds of functionality
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and then make that available to other programs and other libraries,
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so that the community of Python developers can build
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increasingly powerful libraries and programs and frameworks.
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But on the other hand, I am sure you're starting to see
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why managing dependencies manually is so difficult, it's super time consuming,
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copying and pasting source code makes updating really difficult,
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imagine you downloaded some file off the internet, some Python source code
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that you're including in your project,
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what happens if you want to update that file-
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maybe a new version came out or the author released a new version,
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and you want to include that in your program
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to make use of some awesome new features.
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Now, if you have to manually copy and paste that around
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it's very easy to make mistakes and it's kind of hard to understand
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what the real dependencies of a program are.
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So if you are sending that over to a co-worker
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or you want to publish that program on the internet,
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it becomes very hard for everyone else to actually understand
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what dependencies they would need to install
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in order to get your program to run.
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The solution to all of these problems is of course, more software;
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You know, I am joking here, but, there is software
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that can make your life a little bit easier
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when it comes to dependency management,
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and this software is typically referred to as package managers.
