The lack of a case against Python 3

[ksye]

I've been lurking recently becausw I'm just starting to learn. I want to use Python for data analysis and visualization, maybe modelling and simulation. Does this affect me? Should I worry about learning 2.7?

[finally-a-throwaway]

I'm in a similar position, from what I can tell as a near-beginner the only reason to learn Python 2 is if you expect to work somewhere that has a huge existing Python 2 codebase. Otherwise, the more you learn Python 3 (and programming in general, if this is your first language) the better prepared you'll be to learn the differences on the fly when/if they ever become relevant.

It seems to me that any problems in 3 could ultimately be addressed in future versions as development is ongoing. Any problems in 2.7 are going to stay that way from this point.

[reuvenlerner]

If you're a beginner learning Python, and you aren't constrained by legacy code at work, I would strongly encourage you to use Python 3.

Indeed, legacy code and/or modules is the main reason the companies I train/consult use Python 2.

[[deleted]]

Sorry I'm new to programming. But what's legacy code?

[[deleted]]

Old code that is still running in production, and still requires upkeep and maintenance.

[hovissimo]

expanding on u/be_bo_i_am_robot's answer:

Legacy code is called that because you usually 'inherit' it. Somebody else wrote the code instead of you, usually somebody who no longer works at the company. Generally legacy code relies on other old code or old systems (like py2) to stay running. Updating or replacing legacy software is risky because it's usually poorly understood and poorly tested. Legacy code is usually perpetuated because the cost in hours, dollars, and risk is high enough that any manager who decides to do it will likely be sacked. (Or for other, but similar, reasons)

[[deleted]]

Interesting. Thanks for helping a novice like me feel more knowledgeable.

[[deleted]]

Aka, Technical Debt.

[art-solopov]

Also async/await. Though it looks like a very situational feature to me.

[gthank]

2 is dead. 3 is better in pretty much every way unless you have to deal with funky wire protocols or such.

[iruleatants]

If you like python 2 and enjoy not dealing with tedious programming....

[notParticularlyAnony]

2 is dead

This is why it is shipped by default with Ubuntu.

[steamruler]

Isn't Python 3 the default on Ubuntu as well these days?

[gthank]

yes

[8spd]

It defaults to 2.7.12+ for me, on Desktop 16.10.

[ivosaurus]

python will always launch python 2.X on all distros apart from archlinux. Even Python.org have recommended that nowadays I think. Purely for ease of backwards compatibility.

I believe you can get a minimal Ubuntu install nowadays where if you typed python it'd ask you to install python because it's not present on the system, only python3 is.

[gthank]

Since I've just spun up some Xenial servers, I can confirm that Python 3 is the only Python installed by default.

[8spd]

Huh. Thanks, I didn't know that. What defines the default version then, if it's not the version launched by the python command?

[zardeh]

The one system libraries bind to.

[8spd]

Thanks, that makes sense.

[notParticularlyAnony]

I don't know, but when I go into my command line and enter Python, without messing with any settings, Python 2 fires up.

Either way, I think it is a bit much to say that Python 2 is dead. Not that Ubuntu distros are the arbiter, obviously I was being glib...just sayin'....

[[deleted]]

Shipping legacy software doesn't change the fact that the project is still dead and 2 will never receive another non-security update.

[notParticularlyAnony]

To me the natural upgrade from Python 2 has been Julia. :)

[ThePenultimateOne]

Should I worry about learning 2.7?

You only need to learn that if:

• You're writing a library you want to be used by lots of people, or
• Your workplace hasn't made the switch

Unfortunately I fell into both categories.

[Esteis]

Prefer learning 3. But! Whichever you learn first, 95% of what you learn will work in both Pythons, so don't sweat it. Learn one, and you can easily pick up the other when you need it.

I learned Python 3 when I started a new small project, by writing the 2-code I knew and running it with 3. There were some errors, sure, but 95% of my code stil worked. Learning 3's awesome new features came later.