Python mul._keep_coeff函数代码示例

    def as_expr(self):  # Factors
        """Return the underlying expression.

        Examples
        ========

        >>> from sympy.core.exprtools import Factors
        >>> from sympy.abc import x, y
        >>> Factors((x*y**2).as_powers_dict()).as_expr()
        x*y**2

        """

        args = []
        for factor, exp in self.factors.items():
            if exp != 1:
                b, e = factor.as_base_exp()
                if isinstance(exp, int):
                    e = _keep_coeff(Integer(exp), e)
                elif isinstance(exp, Rational):
                    e = _keep_coeff(exp, e)
                else:
                    e *= exp
                args.append(b**e)
            else:
                args.append(factor)
        return Mul(*args)

def gcd_terms(terms, isprimitive=False):
    """
    Compute the GCD of ``terms`` and put them together. If ``isprimitive`` is
    True the _gcd_terms will not run the primitive method on the terms.

    **Examples**

    >>> from sympy.core import gcd_terms
    >>> from sympy.abc import x, y

    >>> gcd_terms((x + 1)**2*y + (x + 1)*y**2)
    y*(x + 1)*(x + y + 1)

    """
    terms = sympify(terms)
    isexpr = isinstance(terms, Expr)
    if not isexpr or terms.is_Add:
        cont, numer, denom = _gcd_terms(terms, isprimitive)
        coeff, factors = cont.as_coeff_Mul()
        return _keep_coeff(coeff, factors*numer/denom)

    if terms.is_Atom:
        return terms

    if terms.is_Mul:
        c, args = terms.as_coeff_mul()
        return _keep_coeff(c, Mul(*[gcd_terms(i, isprimitive) for i in args]))

    def handle(a):
        if iterable(a):
            if isinstance(a, Basic):
                return a.func(*[gcd_terms(i, isprimitive) for i in a.args])
            return type(a)([gcd_terms(i, isprimitive) for i in a])
        return gcd_terms(a, isprimitive)
    return terms.func(*[handle(i) for i in terms.args])

def test_as_content_primitive():
    # although the _as_content_primitive methods do not alter the underlying structure,
    # the as_content_primitive function will touch up the expression and join
    # bases that would otherwise have not been joined.
    assert ((x*(2 + 2*x)*(3*x + 3)**2)).as_content_primitive() ==\
    (18, x*(x + 1)**3)
    assert (2 + 2*x + 2*y*(3 + 3*y)).as_content_primitive() ==\
    (2, x + 3*y*(y + 1) + 1)
    assert ((2 + 6*x)**2).as_content_primitive() ==\
    (4, (3*x + 1)**2)
    assert ((2 + 6*x)**(2*y)).as_content_primitive() ==\
    (1, (_keep_coeff(S(2), (3*x + 1)))**(2*y))
    assert (5 + 10*x + 2*y*(3+3*y)).as_content_primitive() ==\
    (1, 10*x + 6*y*(y + 1) + 5)
    assert ((5*(x*(1 + y)) + 2*x*(3 + 3*y))).as_content_primitive() ==\
    (11, x*(y + 1))
    assert ((5*(x*(1 + y)) + 2*x*(3 + 3*y))**2).as_content_primitive() ==\
    (121, x**2*(y + 1)**2)
    assert (y**2).as_content_primitive() ==\
    (1, y**2)
    assert (S.Infinity).as_content_primitive() == (1, oo)
    eq = x**(2+y)
    assert (eq).as_content_primitive() == (1, eq)
    assert (S.Half**(2 + x)).as_content_primitive() == (S(1)/4, 2**-x)
    assert ((-S.Half)**(2 + x)).as_content_primitive() == \
            (S(1)/4, (-S.Half)**x)
    assert ((-S.Half)**(2 + x)).as_content_primitive() == \
            (S(1)/4, (-S.Half)**x)
    assert (4**((1 + y)/2)).as_content_primitive() == (2, 4**(y/2))
    assert (3**((1 + y)/2)).as_content_primitive() == \
            (1, 3**(Mul(S(1)/2, 1 + y, evaluate=False)))
    assert (5**(S(3)/4)).as_content_primitive() == (1, 5**(S(3)/4))
    assert (5**(S(7)/4)).as_content_primitive() == (5, 5**(S(3)/4))
    assert Add(5*z/7, 0.5*x, 3*y/2, evaluate=False).as_content_primitive() == \
            (S(1)/14, 7.0*x + 21*y + 10*z)

def gcd_terms(terms, isprimitive=False, clear=True):
    """
    Compute the GCD of ``terms`` and put them together. If ``isprimitive`` is
    True the _gcd_terms will not run the primitive method on the terms.

    ``clear`` controls the removal of integers from the denominator of an Add
    expression. When True, all numerical denominator will be cleared; when
    False the denominators will be cleared only if all terms had numerical
    denominators.

    Examples
    ========

    >>> from sympy.core import gcd_terms
    >>> from sympy.abc import x, y

    >>> gcd_terms((x + 1)**2*y + (x + 1)*y**2)
    y*(x + 1)*(x + y + 1)
    >>> gcd_terms(x/2 + 1)
    (x + 2)/2
    >>> gcd_terms(x/2 + 1, clear=False)
    x/2 + 1
    >>> gcd_terms(x/2 + y/2, clear=False)
    (x + y)/2

    """
    terms = sympify(terms)
    isexpr = isinstance(terms, Expr)
    if not isexpr or terms.is_Add:
        cont, numer, denom = _gcd_terms(terms, isprimitive)
        coeff, factors = cont.as_coeff_Mul()
        return _keep_coeff(coeff, factors*numer/denom, clear=clear)

    if terms.is_Atom:
        return terms

    if terms.is_Mul:
        c, args = terms.as_coeff_mul()
        return _keep_coeff(c, Mul(*[gcd_terms(i, isprimitive, clear) for i in args]), clear=clear)

    def handle(a):
        if iterable(a):
            if isinstance(a, Basic):
                return a.func(*[gcd_terms(i, isprimitive, clear) for i in a.args])
            return type(a)([gcd_terms(i, isprimitive, clear) for i in a])
        return gcd_terms(a, isprimitive, clear)
    return terms.func(*[handle(i) for i in terms.args])

    def _print_MatMul(self, expr):
        c, m = expr.as_coeff_mmul()
        if c.is_number and c < 0:
            expr = _keep_coeff(-c, m)
            sign = "-"
        else:
            sign = ""

        return sign + '*'.join([self.parenthesize(arg, precedence(expr))
            for arg in expr.args])

 def as_expr(self):  # Factors
     args = []
     for factor, exp in self.factors.iteritems():
         if exp != 1:
             b, e = factor.as_base_exp()
             e = _keep_coeff(Integer(exp), e)
             args.append(b**e)
         else:
             args.append(factor)
     return Mul(*args)

    def _print_Mul(self, expr):

        prec = precedence(expr)

        c, e = expr.as_coeff_Mul()
        if c < 0:
            expr = _keep_coeff(-c, e)
            sign = "-"
        else:
            sign = ""

        a = []  # items in the numerator
        b = []  # items that are in the denominator (if any)

        pow_paren = []  # Will collect all pow with more than one base element and exp = -1

        if self.order not in ('old', 'none'):
            args = expr.as_ordered_factors()
        else:
            # use make_args in case expr was something like -x -> x
            args = Mul.make_args(expr)

        # Gather args for numerator/denominator
        for item in args:
            if item.is_commutative and item.is_Pow and item.exp.is_Rational and item.exp.is_negative:
                if item.exp != -1:
                    b.append(Pow(item.base, -item.exp, evaluate=False))
                else:
                    if len(item.args[0].args) != 1 and isinstance(item.base, Mul):   # To avoid situations like #14160
                        pow_paren.append(item)
                    b.append(Pow(item.base, -item.exp))
            elif item.is_Rational and item is not S.Infinity:
                if item.p != 1:
                    a.append(Rational(item.p))
                if item.q != 1:
                    b.append(Rational(item.q))
            else:
                a.append(item)

        a = a or [S.One]

        a_str = [self.parenthesize(x, prec, strict=False) for x in a]
        b_str = [self.parenthesize(x, prec, strict=False) for x in b]

        # To parenthesize Pow with exp = -1 and having more than one Symbol
        for item in pow_paren:
            if item.base in b:
                b_str[b.index(item.base)] = "(%s)" % b_str[b.index(item.base)]

        if len(b) == 0:
            return sign + '*'.join(a_str)
        elif len(b) == 1:
            return sign + '*'.join(a_str) + "/" + b_str[0]
        else:
            return sign + '*'.join(a_str) + "/(%s)" % '*'.join(b_str)

def test_factor_terms():
    A = Symbol('A', commutative=False)
    assert factor_terms(9*(x + x*y + 1) + (3*x + 3)**(2 + 2*x)) == \
        9*x*y + 9*x + _keep_coeff(S(3), x + 1)**_keep_coeff(S(2), x + 1) + 9
    assert factor_terms(9*(x + x*y + 1) + (3)**(2 + 2*x)) == \
        _keep_coeff(S(9), 3**(2*x) + x*y + x + 1)
    assert factor_terms(3**(2 + 2*x) + a*3**(2 + 2*x)) == \
        9*3**(2*x)*(a + 1)
    assert factor_terms(x + x*A) == \
        x*(1 + A)
    assert factor_terms(sin(x + x*A)) == \
        sin(x*(1 + A))
    assert factor_terms((3*x + 3)**((2 + 2*x)/3)) == \
        _keep_coeff(S(3), x + 1)**_keep_coeff(S(2)/3, x + 1)
    assert factor_terms(x + (x*y + x)**(3*x + 3)) == \
        x + (x*(y + 1))**_keep_coeff(S(3), x + 1)
    assert factor_terms(a*(x + x*y) + b*(x*2 + y*x*2)) == \
        x*(a + 2*b)*(y + 1)
    i = Integral(x, (x, 0, oo))
    assert factor_terms(i) == i
    eq = sqrt(2) + sqrt(10)
    assert factor_terms(eq) == eq
    assert factor_terms(eq, radical=True) == sqrt(2)*(1 + sqrt(5))
    eq = [x + x*y]
    ans = [x*(y + 1)]
    for c in [list, tuple, set]:
        assert factor_terms(c(eq)) == c(ans)
    assert factor_terms(Tuple(x + x*y)) == Tuple(x*(y + 1))
    assert factor_terms(Interval(0, 1)) == Interval(0, 1)
    e = 1/sqrt(a/2 + 1)
    assert factor_terms(e, clear=False) == 1/sqrt(a/2 + 1)
    assert factor_terms(e, clear=True) == sqrt(2)/sqrt(a + 2)

def factor_terms(expr, radical=False):
    """Remove common factors from terms in all arguments without
    changing the underlying structure of the expr. No expansion or
    simplification (and no processing of non-commutatives) is performed.

    If radical=True then a radical common to all terms will be factored
    out of any Add sub-expressions of the expr.

    Examples
    ========

    >>> from sympy import factor_terms, Symbol
    >>> from sympy.abc import x, y
    >>> factor_terms(x + x*(2 + 4*y)**3)
    x*(8*(2*y + 1)**3 + 1)
    >>> A = Symbol('A', commutative=False)
    >>> factor_terms(x*A + x*A + x*y*A)
    x*(y*A + 2*A)

    """

    expr = sympify(expr)
    is_iterable = iterable(expr)

    if not isinstance(expr, Basic) or expr.is_Atom:
        if is_iterable:
            return type(expr)([factor_terms(i, radical=radical) for i in expr])
        return expr

    if expr.is_Function or is_iterable or not hasattr(expr, 'args_cnc'):
        args = expr.args
        newargs = tuple([factor_terms(i, radical=radical) for i in args])
        if newargs == args:
            return expr
        return expr.func(*newargs)

    cont, p = expr.as_content_primitive(radical=radical)
    list_args, nc = zip(*[ai.args_cnc() for ai in Add.make_args(p)])
    list_args = list(list_args)
    nc = [((Dummy(), Mul._from_args(i)) if i else None) for i in nc]
    ncreps = dict([i for i in nc if i is not None])
    for i, a in enumerate(list_args):
        if nc[i] is not None:
            a.append(nc[i][0])
        a = Mul._from_args(a) # gcd_terms will fix up ordering
        list_args[i] = gcd_terms(a, isprimitive=True)
        # cancel terms that may not have cancelled
    p = Add._from_args(list_args) # gcd_terms will fix up ordering
    p = gcd_terms(p, isprimitive=True).xreplace(ncreps)
    return _keep_coeff(cont, p)

    def _print_Mul(self, expr):

        prec = precedence(expr)

        c, e = expr.as_coeff_Mul()
        if c < 0:
            expr = _keep_coeff(-c, e)
            sign = "-"
        else:
            sign = ""

        a = []  # items in the numerator
        b = []  # items that are in the denominator (if any)

        if self.order not in ('old', 'none'):
            args = expr.as_ordered_factors()
        else:
            # use make_args in case expr was something like -x -> x
            args = Mul.make_args(expr)

        # Gather args for numerator/denominator
        for item in args:
            if item.is_commutative and item.is_Pow and item.exp.is_Rational and item.exp.is_negative:
                if item.exp != -1:
                    b.append(Pow(item.base, -item.exp, evaluate=False))
                else:
                    b.append(Pow(item.base, -item.exp))
            elif item.is_Rational and item is not S.Infinity:
                if item.p != 1:
                    a.append(Rational(item.p))
                if item.q != 1:
                    b.append(Rational(item.q))
            else:
                a.append(item)

        a = a or [S.One]

        a_str = list(map(lambda x: self.parenthesize(x, prec), a))
        b_str = list(map(lambda x: self.parenthesize(x, prec), b))

        if len(b) == 0:
            return sign + '*'.join(a_str)
        elif len(b) == 1:
            if len(a) == 1 and not (a[0].is_Atom or a[0].is_Add):
                return sign + "%s/" % a_str[0] + '*'.join(b_str)
            else:
                return sign + '*'.join(a_str) + "/%s" % b_str[0]
        else:
            return sign + '*'.join(a_str) + "/(%s)" % '*'.join(b_str)

    def _print_Mul(self, expr):
        "Copied from sympy StrPrinter and modified to remove division."

        prec = precedence(expr)

        c, e = expr.as_coeff_Mul()
        if c < 0:
            expr = _keep_coeff(-c, e)
            sign = "-"
        else:
            sign = ""

        a = []  # items in the numerator
        b = []  # items that are in the denominator (if any)

        if self.order not in ('old', 'none'):
            args = expr.as_ordered_factors()
        else:
            # use make_args in case expr was something like -x -> x
            args = Mul.make_args(expr)

        # Gather args for numerator/denominator
        for item in args:
            if item.is_commutative and item.is_Pow and item.exp.is_Rational and item.exp.is_negative:
                if item.exp != -1:
                    b.append(Pow(item.base, -item.exp, evaluate=False))
                else:
                    b.append(Pow(item.base, -item.exp))
            elif item.is_Rational and item is not S.Infinity:
                if item.p != 1:
                    a.append(Rational(item.p))
                if item.q != 1:
                    b.append(Rational(item.q))
            else:
                a.append(item)

        a = a or [S.One]

        a_str = [self.parenthesize(x, prec) for x in a]
        b_str = [self.parenthesize(x, prec) for x in b]

        if len(b) == 0:
            return sign + '*'.join(a_str)
        elif len(b) == 1:
            # Thermo-Calc's parser can't handle division operators
            return sign + '*'.join(a_str) + "*%s" % self.parenthesize(b[0]**(-1), prec)
        else:
            # TODO: Make this Thermo-Calc compatible by removing division operation
            return sign + '*'.join(a_str) + "/(%s)" % '*'.join(b_str)

def test_factor_terms():
    A = Symbol('A', commutative=False)
    assert factor_terms(9*(x + x*y + 1) + (3*x + 3)**(2 + 2*x)) == \
        9*x*y + 9*x + _keep_coeff(S(3), x + 1)**_keep_coeff(S(2), x + 1) + 9
    assert factor_terms(9*(x + x*y + 1) + (3)**(2 + 2*x)) == \
        _keep_coeff(S(9), 3**(2*x) + x*y + x + 1)
    assert factor_terms(3**(2 + 2*x) + a*3**(2 + 2*x)) == \
        9*3**(2*x)*(a + 1)
    assert factor_terms(x + x*A) == \
        x*(1 + A)
    assert factor_terms(sin(x + x*A)) == \
        sin(x*(1 + A))
    assert factor_terms((3*x + 3)**((2 + 2*x)/3)) == \
        _keep_coeff(S(3), x + 1)**_keep_coeff(S(2)/3, x + 1)
    assert factor_terms(x + (x*y + x)**(3*x + 3)) == \
        x + (x*(y + 1))**_keep_coeff(S(3), x + 1)
    assert factor_terms(a*(x + x*y) + b*(x*2 + y*x*2)) == \
        x*(a + 2*b)*(y + 1)
    i = Integral(x, (x, 0, oo))
    assert factor_terms(i) == i

    # check radical extraction
    eq = sqrt(2) + sqrt(10)
    assert factor_terms(eq) == eq
    assert factor_terms(eq, radical=True) == sqrt(2)*(1 + sqrt(5))
    eq = root(-6, 3) + root(6, 3)
    assert factor_terms(eq, radical=True) == 6**(S(1)/3)*(1 + (-1)**(S(1)/3))

    eq = [x + x*y]
    ans = [x*(y + 1)]
    for c in [list, tuple, set]:
        assert factor_terms(c(eq)) == c(ans)
    assert factor_terms(Tuple(x + x*y)) == Tuple(x*(y + 1))
    assert factor_terms(Interval(0, 1)) == Interval(0, 1)
    e = 1/sqrt(a/2 + 1)
    assert factor_terms(e, clear=False) == 1/sqrt(a/2 + 1)
    assert factor_terms(e, clear=True) == sqrt(2)/sqrt(a + 2)

    eq = x/(x + 1/x) + 1/(x**2 + 1)
    assert factor_terms(eq, fraction=False) == eq
    assert factor_terms(eq, fraction=True) == 1

    assert factor_terms((1/(x**3 + x**2) + 2/x**2)*y) == \
        y*(2 + 1/(x + 1))/x**2

    # if not True, then processesing for this in factor_terms is not necessary
    assert gcd_terms(-x - y) == -x - y
    assert factor_terms(-x - y) == Mul(-1, x + y, evaluate=False)

    # if not True, then "special" processesing in factor_terms is not necessary
    assert gcd_terms(exp(Mul(-1, x + 1))) == exp(-x - 1)
    e = exp(-x - 2) + x
    assert factor_terms(e) == exp(Mul(-1, x + 2, evaluate=False)) + x
    assert factor_terms(e, sign=False) == e
    assert factor_terms(exp(-4*x - 2) - x) == -x + exp(Mul(-2, 2*x + 1, evaluate=False))

def decompose_power(expr):
    """
    Decompose power into symbolic base and integer exponent.

    This is strictly only valid if the exponent from which
    the integer is extracted is itself an integer or the
    base is positive. These conditions are assumed and not
    checked here.

    Examples
    ========

    >>> from sympy.core.exprtools import decompose_power
    >>> from sympy.abc import x, y

    >>> decompose_power(x)
    (x, 1)
    >>> decompose_power(x**2)
    (x, 2)
    >>> decompose_power(x**(2*y))
    (x**y, 2)
    >>> decompose_power(x**(2*y/3))
    (x**(y/3), 2)

    """
    base, exp = expr.as_base_exp()

    if exp.is_Number:
        if exp.is_Rational:
            if not exp.is_Integer:
                base = Pow(base, Rational(1, exp.q))

            exp = exp.p
        else:
            base, exp = expr, 1
    else:
        exp, tail = exp.as_coeff_Mul(rational=True)

        if exp is S.NegativeOne:
            base, exp = Pow(base, tail), -1
        elif exp is not S.One:
            tail = _keep_coeff(Rational(1, exp.q), tail)
            base, exp = Pow(base, tail), exp.p
        else:
            base, exp = expr, 1

    return base, exp

    def do(expr):
        from sympy.concrete.summations import Sum
        from sympy.simplify.simplify import factor_sum
        is_iterable = iterable(expr)

        if not isinstance(expr, Basic) or expr.is_Atom:
            if is_iterable:
                return type(expr)([do(i) for i in expr])
            return expr

        if expr.is_Pow or expr.is_Function or \
                is_iterable or not hasattr(expr, 'args_cnc'):
            args = expr.args
            newargs = tuple([do(i) for i in args])
            if newargs == args:
                return expr
            return expr.func(*newargs)

        if isinstance(expr, Sum):
            return factor_sum(expr, radical=radical, clear=clear, fraction=fraction, sign=sign)

        cont, p = expr.as_content_primitive(radical=radical, clear=clear)
        if p.is_Add:
            list_args = [do(a) for a in Add.make_args(p)]
            # get a common negative (if there) which gcd_terms does not remove
            if all(a.as_coeff_Mul()[0].extract_multiplicatively(-1) is not None
                   for a in list_args):
                cont = -cont
                list_args = [-a for a in list_args]
            # watch out for exp(-(x+2)) which gcd_terms will change to exp(-x-2)
            special = {}
            for i, a in enumerate(list_args):
                b, e = a.as_base_exp()
                if e.is_Mul and e != Mul(*e.args):
                    list_args[i] = Dummy()
                    special[list_args[i]] = a
            # rebuild p not worrying about the order which gcd_terms will fix
            p = Add._from_args(list_args)
            p = gcd_terms(p,
                isprimitive=True,
                clear=clear,
                fraction=fraction).xreplace(special)
        elif p.args:
            p = p.func(
                *[do(a) for a in p.args])
        rv = _keep_coeff(cont, p, clear=clear, sign=sign)
        return rv

    def _print_Mul(self, expr):

        prec = precedence(expr)

        c, e = expr.as_coeff_Mul()
        if c < 0:
            expr = _keep_coeff(-c, e)
            sign = "-"
        else:
            sign = ""

        a = []  # items in the numerator
        b = []  # items that are in the denominator (if any)

        if self.order not in ("old", "none"):
            args = expr.as_ordered_factors()
        else:
            # use make_args in case expr was something like -x -> x
            args = Mul.make_args(expr)

        # Gather args for numerator/denominator
        for item in args:
            if item.is_commutative and item.is_Pow and item.exp.is_Rational and item.exp.is_negative:
                if item.exp != -1:
                    b.append(Pow(item.base, -item.exp, evaluate=False))
                else:
                    b.append(Pow(item.base, -item.exp))
            elif item.is_Rational and item is not S.Infinity:
                if item.p != 1:
                    a.append(Rational(item.p))
                if item.q != 1:
                    b.append(Rational(item.q))
            else:
                a.append(item)

        a = a or [S.One]

        a_str = [self.parenthesize(x, prec) for x in a]
        b_str = [self.parenthesize(x, prec) for x in b]

        if len(b) == 0:
            return sign + "*".join(a_str)
        elif len(b) == 1:
            return sign + "*".join(a_str) + "/" + b_str[0]
        else:
            return sign + "*".join(a_str) + "/(%s)" % "*".join(b_str)