67 lines
1.8 KiB
ReStructuredText
67 lines
1.8 KiB
ReStructuredText
.. _why-python3:
|
|
|
|
Why Python 3?
|
|
=============
|
|
|
|
- Python 2.7 is the final Python 2.x release. Python 3.x is the future.
|
|
The Python ecosystem needs to consolidate. A split or schism between
|
|
different incompatible versions is not healthy for growing the
|
|
community.
|
|
- Function annotations
|
|
- Decimal module 100x faster. As fast as floats.
|
|
- Easier to learn. (Less cruft in language and stdlib, more consistency, better docstrings, etc.)
|
|
- Much safer handling of unicode text and encodings: fewer bugs.
|
|
- More memory efficiency (shared dict keys (PEP 412) and space-efficient
|
|
Unicode representation (PEP 393))
|
|
- Exception chaining
|
|
|
|
Why are Unicode strings better on Python 3?
|
|
-------------------------------------------
|
|
|
|
- it is not the default string type (you have to prefix the string
|
|
with a u to get Unicode);
|
|
|
|
- it is missing some functionality, e.g. casefold;
|
|
|
|
- there are two distinct implementations, narrow builds and wide builds;
|
|
|
|
- wide builds take up to four times more memory per string as needed;
|
|
|
|
- narrow builds take up to two times more memory per string as needed;
|
|
|
|
- worse, narrow builds have very naive (possibly even "broken")
|
|
handling of code points in the Supplementary Multilingual Planes.
|
|
|
|
The unicode string type in Python 3 is better because:
|
|
|
|
- it is the default string type;
|
|
|
|
- it includes more functionality;
|
|
|
|
- starting in Python 3.3, it gets rid of the distinction between
|
|
narrow and wide builds;
|
|
|
|
- which reduces the memory overhead of strings by up to a factor
|
|
of four in many cases;
|
|
|
|
- and fixes the issue of SMP code points.
|
|
|
|
(quote from a mailing list post by Steve D'Aprano on 2014-01-17).
|
|
|
|
|
|
New features
|
|
------------
|
|
|
|
Standard library:
|
|
~~~~~~~~~~~~~~~~~
|
|
|
|
- SSL contexts in http.client
|
|
-
|
|
|
|
|
|
|
|
Non-arguments for Python 3
|
|
==========================
|
|
|
|
-
|