Python S-expression emulation using tuple-like objects.
etuples are like tuples:
>>> 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))etuples can also be evaluated:
>>> et.evaled_obj
3Evaluated etuples are cached:
>>> et = etuple(add, "a", "b")
>>> et.evaled_obj
'ab'
>>> et.evaled_obj is et.evaled_obj
TrueReconstructed etuples and their evaluation results are preserved across tuple operations:
>>> et_new = (et[0],) + et[1:]
>>> et_new is et
True
>>> et_new.evaled_obj is et.evaled_obj
Truerator, rands, and apply will return the operator, the operands, and apply the operation to the operands:
>>> 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))
3rator and rands are multipledispatch functions that can be extended to handle arbitrary objects:
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 will convert non-tuple objects into their corresponding etuple form:
>>> et = etuplize(add_node)
>>> pprint(et)
e(+, e(*, 1, 2), 3)
>>> et.evaled_obj is add_node
Trueetuplize can also do shallow object-to-etuple conversions:
>>> et = etuplize(add_node, shallow=True)
>>> pprint(et)
e(+, <__main__.Node at 0x7f347361a080>, 3)Using pip:
pip install etuplesFirst obtain the project source:
git clone git@github.com:pythological/etuples.gitCreate a virtual environment and install the development dependencies:
$ pip install -r requirements.txtSet up pre-commit hooks:
$ pre-commit install --install-hooksTests can be run with the provided Makefile:
make check