utils 0.9.0

枚举

python没有内置的方法来定义枚举，所以这个模块提供了（我认为）一种非常干净的方法来实现它们。

from utils import enum

class Colors(enum.Enum):
    RED = 0
    GREEN = 1

    # Defining an Enum class allows you to specify a few
    # things about the way it's going to behave.
    class Options:
        frozen = True # can't change attributes
        strict = True # can only compare to itself; i.e., Colors.RED == Animals.COW
                      # will raise an exception.

# or use the enum factory (no Options, though)
ColorsAlso = enum.enum("RED", "GREEN")

一旦定义，使用就很简单：

>>> Colors
<class 'blahblah.Colors'>
>>> Colors.RED
<EnumItem: RED [0]>
>>> Colors.RED == 0
True
>>> Colors.RED == Colors.RED
True
>>> Colors.RED = 2
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "utils/enum.py", line 114, in __setattr__
    raise TypeError("can't set attributes on a frozen enum")
TypeError: can't set attributes on a frozen enum

数学

目前只有内置的sum的乘法模拟。

听写

交集，差异，筛选，一些特殊的指令…

列表

扁平化和无列表。还有flat_map！

胸部

当前仅提供xor函数。

日期

对于TimePeriod类来说，最酷的是：

>>> from datetime import date # will also work with datetimes
>>> time_period = TimePeriod(date(2013, 5, 10), date(2013, 8, 11))
>>> time_period
<TimePeriod: 2013-05-10 00:00:00-2013-08-11 23:59:59>
>>> date(2013, 6, 12) in time_period
True
>>> other_time_period = TimePeriod(date(2013, 6, 1), date(2013, 6, 30))
>>> other_time_period in time_period
True
>>> another_time_period = TimePeriod(date(2013, 8, 1), date(2013, 8, 30))
>>> time_period.overlaps(another_time_period)
True
>>> TimePeriod.get_containing_period(time_period, another_time_period)
<TimePeriod: 2013-05-08 00:00:00-2013-08-30 23:59:59>

等等等等。还有一个DiscontinousTimePeriod类，它 存储时间段的集合。

还有一些常用操作的helper函数，如days_ahead和 days_ago，基本上就是他们在罐头上说的。

对象

提供get_attr，这实际上是一种进行深度getattr链接的方便方法：

>>> get_attr(complicated, 'this.is.a.deep.string', default=None)
"the deep string"  # or None, if anything in the lookup chain didn't exist

还有一个immutable实用程序，它将包装一个对象并阻止所有属性更改， 默认情况下是递归的。任何在包装对象上设置属性的尝试都将引发AttributeError：

>>> imm = immutable(something)
>>> imm
<Immutable Something: <Something>>
>>> imm.red
<Immutable SomethingElse: <SomethingElse: red>>
>>> imm.red = SomethingElse('blue')
# ...
AttributeError: This object has been marked as immutable; you cannot set its attributes.
>>> something.red = SomethingElse('blue')
>>> imm.red
<Immutable SomethingElse: <SomethingElse: blue>>

可以通过指定“recursive”标志来切换递归不变性。