为什么我的矩阵不能从字符转换成数字？

matrix = [['1', '2', '3'], ['4', '5', '6']]

# 转换为整数矩阵
numeric_matrix = [[int(char) for char in row] for row in matrix]
print(numeric_matrix)  # 输出: [[1, 2, 3], [4, 5, 6]]

# 转换为浮点数矩阵
numeric_matrix_float = [[float(char) for char in row] for row in matrix]
print(numeric_matrix_float)  # 输出: [[1.0, 2.0, 3.0], [4.0, 5.0, 6.0]]

matrix = [['1', 'a', '3'], ['4', '5', 'b']]

numeric_matrix = []
for row in matrix:
    numeric_row = []
    for char in row:
        try:
            numeric_row.append(int(char))
        except ValueError:
            print(f"无法将 '{char}' 转换为数字，跳过")
    numeric_matrix.append(numeric_row)

print(numeric_matrix)  # 输出: [[1, None, 3], [4, 5, None]]

matrix = [[' 1 ', ' 2 ', ' 3 '], [' 4 ', ' 5 ', ' 6 ']]

numeric_matrix = [[int(char.strip()) for char in row] for row in matrix]
print(numeric_matrix)  # 输出: [[1, 2, 3], [4, 5, 6]]