Real Python - artisanal from-scratch programmers

Hey there,

The other day I got this question from Newsletter member Newvick in my email inbox:

~~~

I found your post on books for people looking to move past the beginner's stage in python, and it was very timely for me.

With that goal in mind, one problem I have is:

When do you use libraries/frameworks and when do you make things from scratch? (whether for learning or developing something for a client/work)

~~~

When to code functionality from scratch and when to use libraries—that's a big question.

There's a fine balance you need to strike here:

When I learned programming I was "reinventing wheels" left and right— and it pushed my abilities forward quickly.

I was constantly writing all kinds of existing functionality from scratch and it was the right thing to do because it helped me grow my skills.

It was a great learning exercise.

But there comes a time in a developers life when that strategy doesn't work so well any more—

Eventually I got diminishing (learning) returns from trying to build everything from scratch.

Plus my development pace was dog-slow.

I spun my wheels—and my productivity began to plateau.

Another downside is this:

It's difficult to work on a team when someone always wants to approach every single problem from first principles. It can drive people NUTS.

These days I try to use (good and well-documented!) third-party libraries where possible.

But again, you'll want to find a balance there too:

I DO NOT recommend you pull in an external dependency for every little thing—

The people who got burned by the NodeJS "left-pad" incident know what I'm talking about...

Actually, this is a fun (ahem) "disaster" story by itself:

There was a little library called "left-pad" on Npm, the NodeJS package repository.

That "library" contained maybe 20 lines of code in total, but it was used in—literally—MILLIONS of JavaScript projects.

It added a tiny piece of functionality that was frequently needed but wasn't a part of the NodeJS standard library.

When the developer who created "left-pad" closed his Npm account last year, "left-pad" was suddenly no longer available for download...

And guess what happened to the dependency install process on projects using "left-pad"...

Well, it came to a SCREECHING HALT.

It was quite crazy. Even some newspapers reported about it.

And there was a lot of "bruhaha" about the NodeJS packaging system.

(But to tell you the truth the same thing could happen with PyPI.)

I guess the moral of the story is:

"Do use 3rd-party libraries and frameworks, but don't overdo it and only go for the trustworthy ones."

Sometimes it's just tough as nails to strike the right balance here...

By the way, if you want to dig deeper—I've got a complete step-by-step workflow for researching and making those dependency decisions (and explaining them to your team/manager) in my "Managing Python Dependencies" course.

But to bring this to a close and answer the original question:

As a rule of thumb, I'd only consider a "let's write it from scratch" strategy IF time is not an issue.

(Which it rarely is outside a pure learning environment.)

Happy Pythoning!

— Dan Bader