多个 TypeErrors 试图在列表理解中乘以列表的元素

Question

我正在关注一本关于深度学习的书，该书鼓励了解更方便的 numpy 替代方案背后的基本数学运算，以便更好地理解基本原理。我正在尝试在本机 Python 3.9 中重建 numpy 的乘法 (*) 运算符，但我得到了一些我觉得非常混乱的 TypeErrors。希望有人可以提供帮助。

def multiply(a, b):

    """ 1.) float * float
        2.) float * vector
        3.) float * matrix
        4.) vector * vector
        5.) vector * matrix
        6.) matrix * matrix """

    def float_float(float_a, float_b):
        return float_a * float_b
    def float_vector(float_a, vector_b):
        return [float_float(float_a, component_b) for component_b in vector_b]
    def float_matrix(float_a, matrix_b):
        return [float_vector(float_a, vector_b) for vector_b in b]
    def vector_vector(vector_a, vector_b):
        return [a * b for a, b in dict(zip(vec_a, vec_b)).items()]
    def vector_matrix(vector_a, matrix_b):
        return [vector_vector(vector_a, vector_b) for vector_b in matrix_b]
    def matrix_matrix(matrix_a, matrix_b):
        return [vector_vector(a, b) for a, b in dict(zip(matrix_a, matrix_b)).items()]

    def get_type(operand):
        if type(operand) == float:
            return "float"
        elif type(operand) == list:
            if any(isinstance(item, list) for item in operand):
                return "matrix"
            else:
                return "vector"

    types = (get_type(a), get_type(b))
    print(types)

    operations_table = {
        ("float", "float"): float_float(a, b),
        ("float", "vector"): float_vector(a, b),
        ("vector", "float"): float_vector(b, a),
        ("float", "matrix"): float_matrix(a, b),
        ("matrix", "float"): float_matrix(b, a),
        ("vector", "vector"): vector_vector(a, b),
        ("vector", "matrix"): vector_matrix(a, b),
        ("matrix", "vector"): vector_matrix(b, a),
        ("matrix", "matrix"): matrix_matrix(a, b)
    }

    return operations_table[types]

# float
f = 2.0
# vector
v = [0.5, 1.0, 2.0]
# matrix
m = [
    [1.0, 2.0, 3.0],
    [4.0, 5.0, 6.0],
    [7.0, 8.0, 9.0]
]

# TEST
print(multiply(f, f))
print(multiply(f, v))
print(multiply(v, m))

这是我在尝试多个 2 个浮点数时遇到的第一个 TypeError：

('float', 'float')
Traceback (most recent call last):
  File "e:\OneDrive\Projects\Deep_Learning\CH05\CH05-000_NativeOps.py", line 62, in <module>
    print(multiply(f, f))
  File "e:\OneDrive\Projects\Deep_Learning\CH05\CH05-000_NativeOps.py", line 38, in multiply
    ("float", "vector"): float_vector(a, b),
  File "e:\OneDrive\Projects\Deep_Learning\CH05\CH05-000_NativeOps.py", line 14, in float_vector
    return [float_float(float_a, component_b) for component_b in vector_b]
TypeError: 'float' object is not iterable

这是我在尝试乘以 float * 向量时遇到的第二个 TypeError

('float', 'vector')
Traceback (most recent call last):
  File "e:\OneDrive\Projects\Deep_Learning\CH05\CH05-000_NativeOps.py", line 63, in <module>
    print(multiply(f, v))
  File "e:\OneDrive\Projects\Deep_Learning\CH05\CH05-000_NativeOps.py", line 37, in multiply
    ("float", "float"): float_float(a, b),
  File "e:\OneDrive\Projects\Deep_Learning\CH05\CH05-000_NativeOps.py", line 12, in float_float
    return float_a * float_b
TypeError: can't multiply sequence by non-int of type 'float'

非常感谢任何帮助，因为在示例中，变量 f、v 和 m 中的所有值都是专门浮动的，所以我对我得到的错误类型感到非常惊讶。谢谢！！！

Answer 1

问题在于操作表字典。无论操作数类型如何，它都会导致所有版本的乘法始终运行。我使用 eval() 将其更改为更短的解决方案，现在代码完美运行。

def multiply(a, b):

    """ 1.) float * float
        2.) float * vector
        3.) float * matrix
        4.) vector * vector
        5.) vector * matrix
        6.) matrix * matrix """

    def float_float(float_a, float_b):
        return float_a * float_b
    def float_vector(float_a, vector_b):
        return [float_float(float_a, component_b) for component_b in vector_b]
    def float_matrix(float_a, matrix_b):
        return [float_vector(float_a, vector_b) for vector_b in b]
    def vector_vector(vector_a, vector_b):
        return [a * b for a, b in list(zip(vector_a, vector_b))]
    def vector_matrix(vector_a, matrix_b):
        return [vector_vector(vector_a, vector_b) for vector_b in matrix_b]
    def matrix_matrix(matrix_a, matrix_b):
        return [vector_vector(a, b) for a, b in list(zip(matrix_a, matrix_b))]

    def get_type(operand):
        if type(operand) == float:
            return "float"
        elif type(operand) == list:
            if any(isinstance(item, list) for item in operand):
                return "matrix"
            else:
                return "vector"

    types = (get_type(a), get_type(b))
    print(types)
    result = eval(f"{types[0]}_{types[1]}(a, b)")
    return result