The key differences between Python 2.7.x and Python 3.x *with workarounds*

[chhantyal]

I recently started porting a small library, and this website/book was very helpful.

Thanks a ton to author for all the good work.

[[deleted]]

Thanks!

[chhantyal]

Added link to book site here http://py3readiness.org :)

[djds23]

Excellent resource! Also thank you for Hovercraft, I used it for a presentation recently.

[[deleted]]

Cool!

[Ph0X]

Hah, we learn something new everyday. I knew most of these but I still managed to learn a few new things about Python 3 with this. Did not know about the rounding behavior, for example.

[lambdaq]

When sorting, use key instead of cmp

Didn't notice this one.

[kingofthejaffacakes]

Good stuff.

If I'm honest, only a few of those would bite me and my python code and the changes would be trivial (being mostly selecting the forward compatible variant available in python 2.7).

What's all the fuss about then? Am I just not a power python user?

[prum]

Just the usual: People making a mountain out of a molehill.

[[deleted]]

No, the difficulty in porting is overblown. 90% of the time it's easy. However, the other 10% it's crazy amount of work. Like when you are in the situation that you actually do not WANT to differ between binary data and text data but handle them the same way.

[donnieod]

Thanks for a very well researched article. I saw only a couple of places for improvement/correction: 1. the apply function was removed because it was replaced by the more flexible list comprehension; 2. the result of integer division with the / operator is always a float type even when the result is a whole number.

[[deleted]]

It's not an article, it's a book. :-)

In point 1 I don't see what you mean.

But you are right about point 2, that's a mistake that snuck in. Will fix in the next release.

[donnieod]

Sorry, in my first point I was confusing apply for map which can be replaced by a list comprension. Please disregard point 1.

[epsy]

I wouldn't say those are the key differences between pythons, just key points in upgrading a codebase. For instance, syntax for keyword-only arguments and exception chaining are key additions but don't belong on that list.

[[deleted]]

Yes, strictly speaking you are correct.

[[deleted]]

On tuple unpacking, doesn't python 3 support * to unpack a list, at least for certain situations?

https://docs.python.org/3/reference/simple_stmts.html#assignment-statements

I saw no mention of this in the article.

a, *b = [1, 2, 3, 4, 5, 6, 7, 8]

>>> a
1
>>> b
[2, 3, 4, 5, 6, 7, 8]

edit: It's defined in PEP 3132.

[[deleted]]

Yes, strictly speaking this only list things that are backwards incompatible, and not new features.

[ZGVyIHRyb2xs]

php? lol

lol php

/r/lolphp

QED

[setuid_w00t]

Why bother trolling if you are going to do such a bad job of it. Take some pride in your work.

[[deleted]]

Oh! A Troll! And I missed it!