From: Vivien Maisonneuve Date: Mon, 23 Jun 2014 12:47:58 +0000 (+0200) Subject: Methods Expression.fromsympy(), Expression.tosympy() X-Git-Tag: 1.0~212 X-Git-Url: https://scm.cri.ensmp.fr/git/linpy.git/commitdiff_plain/8608f67525103a25d5337280fcbdc86d498c5d4e?ds=sidebyside Methods Expression.fromsympy(), Expression.tosympy() --- diff --git a/pypol/linear.py b/pypol/linear.py index eeee698..b69836d 100644 --- a/pypol/linear.py +++ b/pypol/linear.py @@ -329,6 +329,31 @@ class Expression: def __gt__(self, other): return Polyhedron(inequalities=[(self - other)._toint() - 1]) + @classmethod + def fromsympy(cls, expr): + import sympy + coefficients = {} + constant = 0 + for symbol, coefficient in expr.as_coefficients_dict().items(): + coefficient = Fraction(coefficient.p, coefficient.q) + if symbol == sympy.S.One: + constant = coefficient + elif isinstance(symbol, sympy.Symbol): + symbol = symbol.name + coefficients[symbol] = coefficient + else: + raise ValueError('non-linear expression: {!r}'.format(expr)) + return cls(coefficients, constant) + + def tosympy(self): + import sympy + expr = 0 + for symbol, coefficient in self.coefficients(): + term = coefficient * sympy.Symbol(symbol) + expr += term + expr += self.constant + return expr + class Constant(Expression): @@ -361,6 +386,17 @@ class Constant(Expression): return '{}({!r}, {!r})'.format(self.__class__.__name__, self.constant.numerator, self.constant.denominator) + @classmethod + def fromsympy(cls, expr): + import sympy + if isinstance(expr, sympy.Rational): + return cls(expr.p, expr.q) + elif isinstance(expr, numbers.Rational): + return cls(expr) + else: + raise TypeError('expr must be a sympy.Rational instance') + + class Symbol(Expression): __slots__ = Expression.__slots__ + ( @@ -390,6 +426,15 @@ class Symbol(Expression): def __repr__(self): return '{}({!r})'.format(self.__class__.__name__, self._name) + @classmethod + def fromsympy(cls, expr): + import sympy + if isinstance(expr, sympy.Symbol): + return cls(expr.name) + else: + raise TypeError('expr must be a sympy.Symbol instance') + + def symbols(names): if isinstance(names, str): names = names.replace(',', ' ').split() diff --git a/tests/test_linear.py b/tests/test_linear.py index 2375092..b7006a7 100644 --- a/tests/test_linear.py +++ b/tests/test_linear.py @@ -151,10 +151,35 @@ class TestExpression(unittest.TestCase): self.assertEqual((self.x + self.y/2 + self.z/3)._toint(), 6*self.x + 3*self.y + 2*self.z) + def test_fromsympy(self): + import sympy + sp_x, sp_y = sympy.symbols('x y') + self.assertEqual(Expression.fromsympy(sp_x), self.x) + self.assertEqual(Expression.fromsympy(sympy.Rational(22, 7)), self.pi) + self.assertEqual(Expression.fromsympy(sp_x - 2*sp_y + 3), self.expr) + with self.assertRaises(ValueError): + Expression.fromsympy(sp_x*sp_y) + + def test_tosympy(self): + import sympy + sp_x, sp_y = sympy.symbols('x y') + self.assertEqual(self.x.tosympy(), sp_x) + self.assertEqual(self.pi.tosympy(), sympy.Rational(22, 7)) + self.assertEqual(self.expr.tosympy(), sp_x - 2*sp_y + 3) + class TestConstant(unittest.TestCase): - pass + def setUp(self): + self.zero = Constant(0) + self.one = Constant(1) + self.pi = Constant(Fraction(22, 7)) + + def test_fromsympy(self): + import sympy + self.assertEqual(Constant.fromsympy(sympy.Rational(22, 7)), self.pi) + with self.assertRaises(TypeError): + Constant.fromsympy(sympy.Symbol('x')) class TestSymbol(unittest.TestCase): @@ -171,6 +196,17 @@ class TestSymbol(unittest.TestCase): self.assertListEqual(list(symbols('x,y')), [self.x, self.y]) self.assertListEqual(list(symbols(['x', 'y'])), [self.x, self.y]) + def test_fromsympy(self): + import sympy + sp_x = sympy.Symbol('x') + self.assertEqual(Symbol.fromsympy(sp_x), self.x) + with self.assertRaises(TypeError): + Symbol.fromsympy(sympy.Rational(22, 7)) + with self.assertRaises(TypeError): + Symbol.fromsympy(2 * sp_x) + with self.assertRaises(TypeError): + Symbol.fromsympy(sp_x*sp_x) + class TestOperators(unittest.TestCase):