Py3k
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This document summarizes the key changes and new features introduced in Python 3, including: - Strings are now unicode by default and implicit conversions between str and bytes are prohibited. - Integers are unified under int and long is removed. - New features like formatted string literals, function annotations, nonlocal and keyword-only arguments, extended iterable unpacking, comprehensions, exception chaining, and yield from. - New collection abstract base classes and data structures like OrderedDict and Counter. - Metaclasses can now control class creation and new metaclass like OrderedClass is introduced. - Under the hood improvements including a new GIL and stable ABI version tagged shared object files.
![Форматирование строк
"{a:s} {b:.2f}".format(a='строка', b=3.14159)
"{c[0]}-{c[1]}".format(c=(1, 2))
"{0.x}, {0.y}".format(coord)](https://image.slidesharecdn.com/py3k-120401070531-phpapp01/85/Py3k-5-320.jpg)
![OrderedDict
>>> d = {'banana': 3, 'apple':4, 'pear': 1, 'orange':
2}
# dictionary sorted by key
>>> OrderedDict(sorted(d.items(), key=lambda t:
t[0]))
OrderedDict([('apple', 4), ('banana', 3), ('orange',
2), ('pear', 1)])](https://image.slidesharecdn.com/py3k-120401070531-phpapp01/85/Py3k-15-320.jpg)
![Counter
>>> cnt = Counter()
>>> for word in ['red', 'blue', 'red',
… 'green', 'blue', 'blue']:
... cnt[word] += 1
>>> cnt
Counter({'blue': 3, 'red': 2, 'green': 1})](https://image.slidesharecdn.com/py3k-120401070531-phpapp01/85/Py3k-16-320.jpg)
![Yield from
>>> def g(x):
... yield from range(x, 0, -1)
... yield from range(x)
...
>>> list(g(5))
[5, 4, 3, 2, 1, 0, 1, 2, 3, 4]](https://image.slidesharecdn.com/py3k-120401070531-phpapp01/85/Py3k-17-320.jpg)
Py3k
- 1. Python 3 Андрей Светлов @andrew_svetlov [email protected] http://asvetlov.blogspot.com
- 2. Releases 2.6 — Oct 2008 3.0 — Dec 2008 3.1 — Jul 2009 2.7 — Jul 2010 3.2 — Feb 2011 3.3 — Aug 2012
- 3. Строки Только unicode Utf-8 — кодировка по умолчанию Неявные преобразования str↔bytes запрещены.
- 4. Числа Unified int Long — отсутствует Дерево числовых типов Decimal — теперь на C
- 5. Форматирование строк "{a:s} {b:.2f}".format(a='строка', b=3.14159) "{c[0]}-{c[1]}".format(c=(1, 2)) "{0.x}, {0.y}".format(coord)
- 6. Function annotations def f(a: int, b: float) -> str: return "{}:{}".format(a, b) >>> f.__annotations__ {'a': builtins.int, 'b': builtins.float, 'return': builtins.str}
- 7. Nonlocal def f(): a=0 def g(): nonlocal a a += 1 g() return a
- 8. Keyword only >>> def f(a, b=0, *, c, d='Smith'): ... pass >>> f(1, c='John', d='Doe') >>> f(1, c='Mary') >>> f(1) Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: f() needs keyword-only argument c
- 9. Extended iterable unpacking a, *rest = range(5) a, *rest, b = range(5)
- 10. Comprehensions {key(k): value(k) for k in range(5)} {f(k) for k in range(5)} {1, 2, 3, 4, 5}
- 11. ABC and new `super()` class Base(metaclass=abc.ABCMeta): @abc.abstractmethod def f(self, a): """Comprehensive doc""" pass class A(Base): def f(self, a):
- 12. Exception chain def f(): try: 1/0 except Exception as ex: raise RuntimeError("Oops") from ex f()
- 13. Exception chain 2 Traceback (most recent call last): File "<string>", line 3, in f 1/0 ZeroDivisionError: division by zero The above exception was the direct cause of the following exception: Traceback (most recent call last):
- 14. Абстрактные типы для коллекций Hashable Iterable Sized Container Callable Sequence etc.
- 15. OrderedDict >>> d = {'banana': 3, 'apple':4, 'pear': 1, 'orange': 2} # dictionary sorted by key >>> OrderedDict(sorted(d.items(), key=lambda t: t[0])) OrderedDict([('apple', 4), ('banana', 3), ('orange', 2), ('pear', 1)])
- 16. Counter >>> cnt = Counter() >>> for word in ['red', 'blue', 'red', … 'green', 'blue', 'blue']: ... cnt[word] += 1 >>> cnt Counter({'blue': 3, 'red': 2, 'green': 1})
- 17. Yield from >>> def g(x): ... yield from range(x, 0, -1) ... yield from range(x) ... >>> list(g(5)) [5, 4, 3, 2, 1, 0, 1, 2, 3, 4]
- 18. Новые метаклассы class OrderedClass(type): @classmethod def __prepare__(metacls, name, bases, **kwds): return collections.OrderedDict() def __new__(cls, name, bases, classdict): result = type.__new__(cls, name, bases, dict(classdict)) result.members = tuple(classdict)
- 19. Незаметные вкусности Новый GIL Importlib Stable ABI PYC repository dirs ABI version tagged .so files Packaging
- 20. Вопросы? @andrew_svetlov [email protected] http://asvetlov.blogspot.com