GitHub - pythological/etuples: Python S-expression emulation using tuple-like objects. (original) (raw)

etuples

Python S-expression emulation using tuple-like objects.

Examples

etuples are like tuples:

from operator import add from etuples import etuple, etuplize

et = etuple(add, 1, 2) et ExpressionTuple((, 1, 2))

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

et[0:2] ExpressionTuple((, 1))

etuples can also be evaluated:

Evaluated etuples are cached:

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

et.evaled_obj is et.evaled_obj True

Reconstructed 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 True

rator, 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)

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

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

rator 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 True

etuplize can also do shallow object-to-etuple conversions:

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

Installation

Using pip:

Development

First obtain the project source:

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

Create a virtual environment and install the development dependencies:

$ pip install -r requirements.txt

Set up pre-commit hooks:

$ pre-commit install --install-hooks

Tests can be run with the provided Makefile: