Python numpy.float_() Examples

def fenics_to_numpy(fenics_var):
    """Convert FEniCS variable to numpy array"""
    if isinstance(fenics_var, (fenics.Constant, fenics_adjoint.Constant)):
        return fenics_var.values()

    if isinstance(fenics_var, (fenics.Function, fenics_adjoint.Constant)):
        np_array = fenics_var.vector().get_local()
        n_sub = fenics_var.function_space().num_sub_spaces()
        # Reshape if function is multi-component
        if n_sub != 0:
            np_array = np.reshape(np_array, (len(np_array) // n_sub, n_sub))
        return np_array

    if isinstance(fenics_var, fenics.GenericVector):
        return fenics_var.get_local()

    if isinstance(fenics_var, fenics_adjoint.AdjFloat):
        return np.array(float(fenics_var), dtype=np.float_)

    raise ValueError('Cannot convert ' + str(type(fenics_var))) 

def almost(a, b, decimal=6, fill_value=True):
    """
    Returns True if a and b are equal up to decimal places.

    If fill_value is True, masked values considered equal. Otherwise,
    masked values are considered unequal.

    """
    m = mask_or(getmask(a), getmask(b))
    d1 = filled(a)
    d2 = filled(b)
    if d1.dtype.char == "O" or d2.dtype.char == "O":
        return np.equal(d1, d2).ravel()
    x = filled(masked_array(d1, copy=False, mask=m), fill_value).astype(float_)
    y = filled(masked_array(d2, copy=False, mask=m), 1).astype(float_)
    d = np.around(np.abs(x - y), decimal) <= 10.0 ** (-decimal)
    return d.ravel() 

def almost(a, b, decimal=6, fill_value=True):
    """
    Returns True if a and b are equal up to decimal places.

    If fill_value is True, masked values considered equal. Otherwise,
    masked values are considered unequal.

    """
    m = mask_or(getmask(a), getmask(b))
    d1 = filled(a)
    d2 = filled(b)
    if d1.dtype.char == "O" or d2.dtype.char == "O":
        return np.equal(d1, d2).ravel()
    x = filled(masked_array(d1, copy=False, mask=m), fill_value).astype(float_)
    y = filled(masked_array(d2, copy=False, mask=m), 1).astype(float_)
    d = np.around(np.abs(x - y), decimal) <= 10.0 ** (-decimal)
    return d.ravel() 

def approx(a, b, fill_value=True, rtol=1e-5, atol=1e-8):
    """
    Returns true if all components of a and b are equal to given tolerances.

    If fill_value is True, masked values considered equal. Otherwise,
    masked values are considered unequal.  The relative error rtol should
    be positive and << 1.0 The absolute error atol comes into play for
    those elements of b that are very small or zero; it says how small a
    must be also.

    """
    m = mask_or(getmask(a), getmask(b))
    d1 = filled(a)
    d2 = filled(b)
    if d1.dtype.char == "O" or d2.dtype.char == "O":
        return np.equal(d1, d2).ravel()
    x = filled(masked_array(d1, copy=False, mask=m), fill_value).astype(float_)
    y = filled(masked_array(d2, copy=False, mask=m), 1).astype(float_)
    d = np.less_equal(umath.absolute(x - y), atol + rtol * umath.absolute(y))
    return d.ravel() 

def testFrexp(self):
        t1 = ones((3, 4, 5), chunk_size=2)
        t2 = empty((3, 4, 5), dtype=np.float_, chunk_size=2)
        op_type = type(t1.op)

        o1, o2 = frexp(t1)

        self.assertIs(o1.op, o2.op)
        self.assertNotEqual(o1.dtype, o2.dtype)

        o1, o2 = frexp(t1, t1)

        self.assertIs(o1, t1)
        self.assertIsNot(o1.inputs[0], t1)
        self.assertIsInstance(o1.inputs[0].op, op_type)
        self.assertIsNot(o2.inputs[0], t1)

        o1, o2 = frexp(t1, t2, where=t1 > 0)

        op_type = type(t2.op)
        self.assertIs(o1, t2)
        self.assertIsNot(o1.inputs[0], t1)
        self.assertIsInstance(o1.inputs[0].op, op_type)
        self.assertIsNot(o2.inputs[0], t1) 

def testArrayProtocol(self):
        arr = mt.ones((10, 20))

        result = np.asarray(arr)
        np.testing.assert_array_equal(result, np.ones((10, 20)))

        arr2 = mt.ones((10, 20))

        result = np.asarray(arr2, mt.bool_)
        np.testing.assert_array_equal(result, np.ones((10, 20), dtype=np.bool_))

        arr3 = mt.ones((10, 20)).sum()

        result = np.asarray(arr3)
        np.testing.assert_array_equal(result, np.asarray(200))

        arr4 = mt.ones((10, 20)).sum()

        result = np.asarray(arr4, dtype=np.float_)
        np.testing.assert_array_equal(result, np.asarray(200, dtype=np.float_)) 

def test_empty_tuple_index(self):
        # Empty tuple index creates a view
        a = np.array([1, 2, 3])
        assert_equal(a[()], a)
        assert_(a[()].base is a)
        a = np.array(0)
        assert_(isinstance(a[()], np.int_))

        # Regression, it needs to fall through integer and fancy indexing
        # cases, so need the with statement to ignore the non-integer error.
        with warnings.catch_warnings():
            warnings.filterwarnings('ignore', '', DeprecationWarning)
            a = np.array([1.])
            assert_(isinstance(a[0.], np.float_))

            a = np.array([np.array(1)], dtype=object)
            assert_(isinstance(a[0.], np.ndarray)) 

def test_fromValue(self, datetime_series):

        nans = Series(np.NaN, index=datetime_series.index)
        assert nans.dtype == np.float_
        assert len(nans) == len(datetime_series)

        strings = Series('foo', index=datetime_series.index)
        assert strings.dtype == np.object_
        assert len(strings) == len(datetime_series)

        d = datetime.now()
        dates = Series(d, index=datetime_series.index)
        assert dates.dtype == 'M8[ns]'
        assert len(dates) == len(datetime_series)

        # GH12336
        # Test construction of categorical series from value
        categorical = Series(0, index=datetime_series.index, dtype="category")
        expected = Series(0, index=datetime_series.index).astype("category")
        assert categorical.dtype == 'category'
        assert len(categorical) == len(datetime_series)
        tm.assert_series_equal(categorical, expected) 

def approx(a, b, fill_value=True, rtol=1e-5, atol=1e-8):
    """
    Returns true if all components of a and b are equal to given tolerances.

    If fill_value is True, masked values considered equal. Otherwise,
    masked values are considered unequal.  The relative error rtol should
    be positive and << 1.0 The absolute error atol comes into play for
    those elements of b that are very small or zero; it says how small a
    must be also.

    """
    m = mask_or(getmask(a), getmask(b))
    d1 = filled(a)
    d2 = filled(b)
    if d1.dtype.char == "O" or d2.dtype.char == "O":
        return np.equal(d1, d2).ravel()
    x = filled(masked_array(d1, copy=False, mask=m), fill_value).astype(float_)
    y = filled(masked_array(d2, copy=False, mask=m), 1).astype(float_)
    d = np.less_equal(umath.absolute(x - y), atol + rtol * umath.absolute(y))
    return d.ravel() 

def almost(a, b, decimal=6, fill_value=True):
    """
    Returns True if a and b are equal up to decimal places.

    If fill_value is True, masked values considered equal. Otherwise,
    masked values are considered unequal.

    """
    m = mask_or(getmask(a), getmask(b))
    d1 = filled(a)
    d2 = filled(b)
    if d1.dtype.char == "O" or d2.dtype.char == "O":
        return np.equal(d1, d2).ravel()
    x = filled(masked_array(d1, copy=False, mask=m), fill_value).astype(float_)
    y = filled(masked_array(d2, copy=False, mask=m), 1).astype(float_)
    d = np.around(np.abs(x - y), decimal) <= 10.0 ** (-decimal)
    return d.ravel() 

def approx(a, b, fill_value=True, rtol=1e-5, atol=1e-8):
    """
    Returns true if all components of a and b are equal to given tolerances.

    If fill_value is True, masked values considered equal. Otherwise,
    masked values are considered unequal.  The relative error rtol should
    be positive and << 1.0 The absolute error atol comes into play for
    those elements of b that are very small or zero; it says how small a
    must be also.

    """
    m = mask_or(getmask(a), getmask(b))
    d1 = filled(a)
    d2 = filled(b)
    if d1.dtype.char == "O" or d2.dtype.char == "O":
        return np.equal(d1, d2).ravel()
    x = filled(masked_array(d1, copy=False, mask=m), fill_value).astype(float_)
    y = filled(masked_array(d2, copy=False, mask=m), 1).astype(float_)
    d = np.less_equal(umath.absolute(x - y), atol + rtol * umath.absolute(y))
    return d.ravel() 

def approx(a, b, fill_value=True, rtol=1e-5, atol=1e-8):
    """
    Returns true if all components of a and b are equal to given tolerances.

    If fill_value is True, masked values considered equal. Otherwise,
    masked values are considered unequal.  The relative error rtol should
    be positive and << 1.0 The absolute error atol comes into play for
    those elements of b that are very small or zero; it says how small a
    must be also.

    """
    m = mask_or(getmask(a), getmask(b))
    d1 = filled(a)
    d2 = filled(b)
    if d1.dtype.char == "O" or d2.dtype.char == "O":
        return np.equal(d1, d2).ravel()
    x = filled(masked_array(d1, copy=False, mask=m), fill_value).astype(float_)
    y = filled(masked_array(d2, copy=False, mask=m), 1).astype(float_)
    d = np.less_equal(umath.absolute(x - y), atol + rtol * umath.absolute(y))
    return d.ravel() 

def approx(a, b, fill_value=True, rtol=1e-5, atol=1e-8):
    """
    Returns true if all components of a and b are equal to given tolerances.

    If fill_value is True, masked values considered equal. Otherwise,
    masked values are considered unequal.  The relative error rtol should
    be positive and << 1.0 The absolute error atol comes into play for
    those elements of b that are very small or zero; it says how small a
    must be also.

    """
    m = mask_or(getmask(a), getmask(b))
    d1 = filled(a)
    d2 = filled(b)
    if d1.dtype.char == "O" or d2.dtype.char == "O":
        return np.equal(d1, d2).ravel()
    x = filled(masked_array(d1, copy=False, mask=m), fill_value).astype(float_)
    y = filled(masked_array(d2, copy=False, mask=m), 1).astype(float_)
    d = np.less_equal(umath.absolute(x - y), atol + rtol * umath.absolute(y))
    return d.ravel() 

def almost(a, b, decimal=6, fill_value=True):
    """
    Returns True if a and b are equal up to decimal places.

    If fill_value is True, masked values considered equal. Otherwise,
    masked values are considered unequal.

    """
    m = mask_or(getmask(a), getmask(b))
    d1 = filled(a)
    d2 = filled(b)
    if d1.dtype.char == "O" or d2.dtype.char == "O":
        return np.equal(d1, d2).ravel()
    x = filled(masked_array(d1, copy=False, mask=m), fill_value).astype(float_)
    y = filled(masked_array(d2, copy=False, mask=m), 1).astype(float_)
    d = np.around(np.abs(x - y), decimal) <= 10.0 ** (-decimal)
    return d.ravel() 

def test_nan(self):
        # nans should be passed through, not converted to infs
        ps = [None, 1, -1, 2, -2, 'fro']
        p_pos = [None, 1, 2, 'fro']

        A = np.ones((2, 2))
        A[0,1] = np.nan
        for p in ps:
            c = linalg.cond(A, p)
            assert_(isinstance(c, np.float_))
            assert_(np.isnan(c))

        A = np.ones((3, 2, 2))
        A[1,0,1] = np.nan
        for p in ps:
            c = linalg.cond(A, p)
            assert_(np.isnan(c[1]))
            if p in p_pos:
                assert_(c[0] > 1e15)
                assert_(c[2] > 1e15)
            else:
                assert_(not np.isnan(c[0]))
                assert_(not np.isnan(c[2])) 

def test_numpy_float_python_long_addition(self):
        # Check that numpy float and python longs can be added correctly.
        a = np.float_(23.) + 2**135
        assert_equal(a, 23. + 2**135) 

def test_testAverage2(self):
        # More tests of average.
        w1 = [0, 1, 1, 1, 1, 0]
        w2 = [[0, 1, 1, 1, 1, 0], [1, 0, 0, 0, 0, 1]]
        x = arange(6, dtype=np.float_)
        assert_equal(average(x, axis=0), 2.5)
        assert_equal(average(x, axis=0, weights=w1), 2.5)
        y = array([arange(6, dtype=np.float_), 2.0 * arange(6)])
        assert_equal(average(y, None), np.add.reduce(np.arange(6)) * 3. / 12.)
        assert_equal(average(y, axis=0), np.arange(6) * 3. / 2.)
        assert_equal(average(y, axis=1),
                     [average(x, axis=0), average(x, axis=0) * 2.0])
        assert_equal(average(y, None, weights=w2), 20. / 6.)
        assert_equal(average(y, axis=0, weights=w2),
                     [0., 1., 2., 3., 4., 10.])
        assert_equal(average(y, axis=1),
                     [average(x, axis=0), average(x, axis=0) * 2.0])
        m1 = zeros(6)
        m2 = [0, 0, 1, 1, 0, 0]
        m3 = [[0, 0, 1, 1, 0, 0], [0, 1, 1, 1, 1, 0]]
        m4 = ones(6)
        m5 = [0, 1, 1, 1, 1, 1]
        assert_equal(average(masked_array(x, m1), axis=0), 2.5)
        assert_equal(average(masked_array(x, m2), axis=0), 2.5)
        assert_equal(average(masked_array(x, m4), axis=0).mask, [True])
        assert_equal(average(masked_array(x, m5), axis=0), 0.0)
        assert_equal(count(average(masked_array(x, m4), axis=0)), 0)
        z = masked_array(y, m3)
        assert_equal(average(z, None), 20. / 6.)
        assert_equal(average(z, axis=0), [0., 1., 99., 99., 4.0, 7.5])
        assert_equal(average(z, axis=1), [2.5, 5.0])
        assert_equal(average(z, axis=0, weights=w2),
                     [0., 1., 99., 99., 4.0, 10.0]) 

def __init__(self,  obj):

        if isinstance(obj, SolutionPool):

            self._P = obj.P
            self._objvals = obj.objvals
            self._solutions = obj.solutions

        elif isinstance(obj, int):

            assert obj >= 1
            self._P = int(obj)
            self._objvals = np.empty(0)
            self._solutions = np.empty(shape = (0, self._P))

        elif isinstance(obj, dict):

            assert len(obj) == 2
            objvals = np.copy(obj['objvals']).flatten().astype(dtype = np.float_)
            solutions = np.copy(obj['solutions'])
            n = objvals.size
            if solutions.ndim == 2:
                assert n in solutions.shape
                if solutions.shape[1] == n and solutions.shape[0] != n:
                    solutions = np.transpose(solutions)
            elif solutions.ndim == 1:
                assert n == 1
                solutions = np.reshape(solutions, (1, solutions.size))
            else:
                raise ValueError('solutions has more than 2 dimensions')

            self._P = solutions.shape[1]
            self._objvals = objvals
            self._solutions = solutions

        else:
            raise ValueError('cannot initialize SolutionPool using %s object' % type(obj)) 

def test_scalar_return_type(self):
        # Full scalar indices should return scalars and object
        # arrays should not call PyArray_Return on their items
        class Zero(object):
            # The most basic valid indexing
            def __index__(self):
                return 0

        z = Zero()

        class ArrayLike(object):
            # Simple array, should behave like the array
            def __array__(self):
                return np.array(0)

        a = np.zeros(())
        assert_(isinstance(a[()], np.float_))
        a = np.zeros(1)
        assert_(isinstance(a[z], np.float_))
        a = np.zeros((1, 1))
        assert_(isinstance(a[z, np.array(0)], np.float_))
        assert_(isinstance(a[z, ArrayLike()], np.float_))

        # And object arrays do not call it too often:
        b = np.array(0)
        a = np.array(0, dtype=object)
        a[()] = b
        assert_(isinstance(a[()], np.ndarray))
        a = np.array([b, None])
        assert_(isinstance(a[z], np.ndarray))
        a = np.array([[b, None]])
        assert_(isinstance(a[z, np.array(0)], np.ndarray))
        assert_(isinstance(a[z, ArrayLike()], np.ndarray)) 

def test_non_integer_sequence_multiplication(self):
        # Numpy scalar sequence multiply should not work with non-integers
        def mult(a, b):
            return a * b

        self.assert_deprecated(mult, args=([1], np.float_(3)))
        self.assert_not_deprecated(mult, args=([1], np.int_(3))) 

def __iter__(self):
        lengths = np.array(
            [(-l[0], -l[1], np.random.random()) for l in self.lengths],
            dtype=[('l1', np.int_), ('l2', np.int_), ('rand', np.float_)]
        )
        indices = np.argsort(lengths, order=('l1', 'l2', 'rand'))
        batches = [indices[i:i + self.batch_size]
                   for i in range(0, len(indices), self.batch_size)]
        if self.shuffle:
            np.random.shuffle(batches)
        return iter([i for batch in batches for i in batch]) 

def test_ptp(self):
        (x, X, XX, m, mx, mX, mXX,) = self.d
        (n, m) = X.shape
        self.assertEqual(mx.ptp(), mx.compressed().ptp())
        rows = np.zeros(n, np.float_)
        cols = np.zeros(m, np.float_)
        for k in range(m):
            cols[k] = mX[:, k].compressed().ptp()
        for k in range(n):
            rows[k] = mX[k].compressed().ptp()
        self.assertTrue(eq(mX.ptp(0), cols))
        self.assertTrue(eq(mX.ptp(1), rows)) 

def test_testAverage2(self):
        # More tests of average.
        w1 = [0, 1, 1, 1, 1, 0]
        w2 = [[0, 1, 1, 1, 1, 0], [1, 0, 0, 0, 0, 1]]
        x = arange(6, dtype=np.float_)
        assert_equal(average(x, axis=0), 2.5)
        assert_equal(average(x, axis=0, weights=w1), 2.5)
        y = array([arange(6, dtype=np.float_), 2.0 * arange(6)])
        assert_equal(average(y, None), np.add.reduce(np.arange(6)) * 3. / 12.)
        assert_equal(average(y, axis=0), np.arange(6) * 3. / 2.)
        assert_equal(average(y, axis=1),
                     [average(x, axis=0), average(x, axis=0) * 2.0])
        assert_equal(average(y, None, weights=w2), 20. / 6.)
        assert_equal(average(y, axis=0, weights=w2),
                     [0., 1., 2., 3., 4., 10.])
        assert_equal(average(y, axis=1),
                     [average(x, axis=0), average(x, axis=0) * 2.0])
        m1 = zeros(6)
        m2 = [0, 0, 1, 1, 0, 0]
        m3 = [[0, 0, 1, 1, 0, 0], [0, 1, 1, 1, 1, 0]]
        m4 = ones(6)
        m5 = [0, 1, 1, 1, 1, 1]
        assert_equal(average(masked_array(x, m1), axis=0), 2.5)
        assert_equal(average(masked_array(x, m2), axis=0), 2.5)
        assert_equal(average(masked_array(x, m4), axis=0).mask, [True])
        assert_equal(average(masked_array(x, m5), axis=0), 0.0)
        assert_equal(count(average(masked_array(x, m4), axis=0)), 0)
        z = masked_array(y, m3)
        assert_equal(average(z, None), 20. / 6.)
        assert_equal(average(z, axis=0), [0., 1., 99., 99., 4.0, 7.5])
        assert_equal(average(z, axis=1), [2.5, 5.0])
        assert_equal(average(z, axis=0, weights=w2),
                     [0., 1., 99., 99., 4.0, 10.0]) 

def test_testAverage2(self):
        # More tests of average.
        w1 = [0, 1, 1, 1, 1, 0]
        w2 = [[0, 1, 1, 1, 1, 0], [1, 0, 0, 0, 0, 1]]
        x = arange(6, dtype=np.float_)
        assert_equal(average(x, axis=0), 2.5)
        assert_equal(average(x, axis=0, weights=w1), 2.5)
        y = array([arange(6, dtype=np.float_), 2.0 * arange(6)])
        assert_equal(average(y, None), np.add.reduce(np.arange(6)) * 3. / 12.)
        assert_equal(average(y, axis=0), np.arange(6) * 3. / 2.)
        assert_equal(average(y, axis=1),
                     [average(x, axis=0), average(x, axis=0) * 2.0])
        assert_equal(average(y, None, weights=w2), 20. / 6.)
        assert_equal(average(y, axis=0, weights=w2),
                     [0., 1., 2., 3., 4., 10.])
        assert_equal(average(y, axis=1),
                     [average(x, axis=0), average(x, axis=0) * 2.0])
        m1 = zeros(6)
        m2 = [0, 0, 1, 1, 0, 0]
        m3 = [[0, 0, 1, 1, 0, 0], [0, 1, 1, 1, 1, 0]]
        m4 = ones(6)
        m5 = [0, 1, 1, 1, 1, 1]
        assert_equal(average(masked_array(x, m1), axis=0), 2.5)
        assert_equal(average(masked_array(x, m2), axis=0), 2.5)
        assert_equal(average(masked_array(x, m4), axis=0).mask, [True])
        assert_equal(average(masked_array(x, m5), axis=0), 0.0)
        assert_equal(count(average(masked_array(x, m4), axis=0)), 0)
        z = masked_array(y, m3)
        assert_equal(average(z, None), 20. / 6.)
        assert_equal(average(z, axis=0), [0., 1., 99., 99., 4.0, 7.5])
        assert_equal(average(z, axis=1), [2.5, 5.0])
        assert_equal(average(z, axis=0, weights=w2),
                     [0., 1., 99., 99., 4.0, 10.0]) 

def __call__(self, *args):
        args = [np.asarray(x) for x in args]
        if not all([x.shape == y.shape for x in args for y in args]):
            raise ValueError("Array lengths must be equal")
        shp = args[0].shape
        xa = np.asarray([a.flatten() for a in args], dtype=np.float_)
        r = self._call_norm(xa, self.xi)
        return np.dot(self._function(r), self.nodes).reshape(shp) 

def __init__(self, *args, **kwargs):
        self.xi = np.asarray([np.asarray(a, dtype=np.float_).flatten()
                           for a in args[:-1]])
        self.N = self.xi.shape[-1]
        self.di = np.asarray(args[-1]).flatten()

        if not all([x.size == self.di.size for x in self.xi]):
            raise ValueError("All arrays must be equal length.")

        self.norm = kwargs.pop('norm', self._euclidean_norm)
        self.epsilon = kwargs.pop('epsilon', None)
        if self.epsilon is None:
            # default epsilon is the "the average distance between nodes" based
            # on a bounding hypercube
            dim = self.xi.shape[0]
            ximax = np.amax(self.xi, axis=1)
            ximin = np.amin(self.xi, axis=1)
            edges = ximax-ximin
            edges = edges[np.nonzero(edges)]
            self.epsilon = np.power(np.prod(edges)/self.N, 1.0/edges.size)
        self.smooth = kwargs.pop('smooth', 0.0)

        self.function = kwargs.pop('function', 'multiquadric')

        # attach anything left in kwargs to self
        #  for use by any user-callable function or
        #  to save on the object returned.
        for item, value in kwargs.items():
            setattr(self, item, value)

        self.nodes = linalg.solve(self.A, self.di) 

def get_sum_dtype(dtype):
    """Mimic numpy's casting for np.sum"""
    if np.issubdtype(dtype, np.float_):
        return np.float_
    if dtype.kind == 'u' and np.can_cast(dtype, np.uint):
        return np.uint
    if np.can_cast(dtype, np.int_):
        return np.int_
    return dtype 

def __new__(cls, input_array, *a, **kw):
        # allways make a copy of input paramters, as we need it to be in C order:
        if not isinstance(input_array, ObsAr):
            try:
                # try to cast ints to floats
                obj = np.atleast_1d(np.require(input_array, dtype=np.float_, requirements=['W', 'C'])).view(cls)
            except ValueError:
                # do we have other dtypes in the array?
                obj = np.atleast_1d(np.require(input_array, requirements=['W', 'C'])).view(cls)
        else: obj = input_array
        super(ObsAr, obj).__init__(*a, **kw)
        return obj 

def test_casting(self):
        ints = np.array(range(10))
        self.assertEqual(ints.dtype, np.int_)
        floats = np.arange(0,5,.5)
        self.assertEqual(floats.dtype, np.float_)
        strings = np.array(list('testing'))
        self.assertEqual(strings.dtype.type, np.str_)

        self.assertEqual(ObsAr(ints).dtype, np.float_)
        self.assertEqual(ObsAr(floats).dtype, np.float_)
        self.assertEqual(ObsAr(strings).dtype.type, np.str_) 

def mutable_tensor(name, shape=None, dtype=np.float_, fill_value=None, chunk_size=None):
    """
    Create or get a mutable tensor using the local or default session.

    When `shape` is `None`, it will try to get the mutable tensor with name `name`. Otherwise,
    it will try to create a mutable tensor using the provided `name` and `shape`.

    Parameters
    ----------
    name : str
        Name of the mutable tensor.
    shape : int or sequence of ints
        Shape of the new mutable tensor, e.g., ``(2, 3)`` or ``2``.
    dtype : data-type, optional
        The desired data-type for the mutable tensor, e.g., `mt.int8`.  Default is `mt.float_`.
    chunk_size: int or tuple of ints, optional
        Specifies chunk size for each dimension.
    fill_value: scalar, optional
        The created mutable tensor will be filled by `fill_value` defaultly, if the parameter is None,
        the newly created mutable tensor will be initialized with `np.zeros`. See also `numpy.full`.
    """
    from ..session import Session
    session = Session.default_or_local()

    if shape is None:
        return session.get_mutable_tensor(name)
    else:
        return session.create_mutable_tensor(name, shape=shape, dtype=dtype,
                                             fill_value=fill_value, chunk_size=chunk_size)