iter(dict) is equivalent to iter(dict.keys()), so simply act on the dict
instead of adding the extra call.
Inspired by Lennart Regebro's PyCon 2017 presentation "Prehistoric
Patterns in Python". Available at:
https://www.youtube.com/watch?v=V5-JH23Vk0I
There are two main issues fixed with this commit:
* bytes vs. str: All file, image, and palette data are now handled as
bytes. A new _binary module consolidates the hacks needed to do this
across Python versions. tostring/fromstring methods have been renamed to
tobytes/frombytes, but the Python 2.6/2.7 versions alias them to the old
names for compatibility. Users should move to tobytes/frombytes.
One other potentially-breaking change is that text data in image files
(such as tags, comments) are now explicitly handled with a specific
character encoding in mind. This works well with the Unicode str in
Python 3, but may trip up old code expecting a straight byte-for-byte
translation to a Python string. This also required a change to Gohlke's
tags tests (in Tests/test_file_png.py) to expect Unicode strings from
the code.
* True div vs. floor div: Many division operations used the "/" operator
to do floor division, which is now the "//" operator in Python 3. These
were fixed.
As of this commit, on the first pass, I have one failing test (improper
handling of a slice object in a C module, test_imagepath.py) in Python 3,
and three that that I haven't tried running yet (test_imagegl,
test_imagegrab, and test_imageqt). I also haven't tested anything on
Windows. All but the three skipped tests run flawlessly against Pythons
2.6 and 2.7.
This is, I guess, a few things the Python devs were just fed up with.
* "while 1" is now "while True"
* Types are compared with isinstance instead of ==
* Sort a list in one go with sorted()
My own twist is to also replace type('') with str, type(()) with tuple,
type([]) with list, type(1) with int, and type(5000.0) with float.
In py3k, imports are absolute unless using the "from . import" syntax.
This commit also solves a recursive import between Image, ImageColor, and
ImagePalette by delay-importing ImagePalette in Image.
I'm not too keen on this commit because the syntax is ugly. I might go back
and prefer the prettier "from PIL import".
y.has_key(x) is gone (use x in y), and keys(), values(), items(), and
range() all return views.
Some iterables needed to be packed into lists, either because the code
expected a list (such as "range(256) * 3") or because the original
collection was being modified (automatic global declarations).
The Tiff ImageFileDictionary is a special case and will be dealt with in
another commit.
