etuples

使用类似于元组的对象来模拟Python S表达式。

示例

etuple就像元组

>>> from operator import add
>>> from etuples import etuple, etuplize

>>> et = etuple(add, 1, 2)
>>> et
ExpressionTuple((<built-in function add>, 1, 2))

>>> from IPython.lib.pretty import pprint
>>> pprint(et)
e(<function _operator.add(a, b, /)>, 1, 2)

>>> et[0:2]
ExpressionTuple((<built-in function add>, 1))

etuple也可以被评估

>>> et.evaled_obj
3

已评估的etuple会被缓存

>>> et = etuple(add, "a", "b")
>>> et.evaled_obj
'ab'

>>> et.evaled_obj is et.evaled_obj
True

重建的etuple及其评估结果会在元组操作间保持

>>> et_new = (et[0],) + et[1:]
>>> et_new is et
True
>>> et_new.evaled_obj is et.evaled_obj
True

rator、rands和apply会返回操作符、操作数并将操作应用于操作数

>>> from etuples import rator, rands, apply
>>> et = etuple(add, 1, 2)

>>> rator(et)
<built-in function add>

>>> rands(et)
ExpressionTuple((1, 2))

>>> apply(rator(et), rands(et))
3

rator和rands是multipledispatch函数，可以扩展以处理任意对象

from etuples.core import ExpressionTuple
from collections.abc import Sequence


class Node:
    def __init__(self, rator, rands):
        self.rator, self.rands = rator, rands

    def __eq__(self, other):
        return self.rator == other.rator and self.rands == other.rands


class Operator:
    def __init__(self, op_name):
        self.op_name = op_name

    def __call__(self, *args):
        return Node(Operator(self.op_name), args)

    def __repr__(self):
        return self.op_name

    def __eq__(self, other):
        return self.op_name == other.op_name


rands.add((Node,), lambda x: x.rands)
rator.add((Node,), lambda x: x.rator)


@apply.register(Operator, (Sequence, ExpressionTuple))
def apply_Operator(rator, rands):
    return Node(rator, rands)

>>> mul_op, add_op = Operator("*"), Operator("+")
>>> mul_node = Node(mul_op, [1, 2])
>>> add_node = Node(add_op, [mul_node, 3])

etuplize会将非元组对象转换为相应的etuple形式

>>> et = etuplize(add_node)
>>> pprint(et)
e(+, e(*, 1, 2), 3)

>>> et.evaled_obj is add_node
True

etuplize还可以进行浅对象到etuple的转换

>>> et = etuplize(add_node, shallow=True)
>>> pprint(et)
e(+, <__main__.Node at 0x7f347361a080>, 3)

安装

使用pip

pip install etuples

开发

首先获取项目源代码

git clone git@github.com:pythological/etuples.git

创建虚拟环境并安装开发依赖项

$ pip install -r requirements.txt

设置pre-commit钩子

$ pre-commit install --install-hooks

可以使用提供的Makefile运行测试

make check