在 Python 函数中不使用 try/except 的错误处理

Question

我写了这个 python 函数。项目规范不允许我使用 try/except 来处理错误。根据文档字符串，如果成功，我应该返回 False，如果失败，则返回 True，我将调用 declare_error 函数。在 main 函数中处理的行号。

注意，除了 sys 和 os，我不允许导入任何东西，所以使用正则表达式是不可能的。

这是我的代码。关于 if/else 语句我应该使用什么的任何建议？

#===============================================================================
def read_subsequent_lines(file_object, line_number, simulation_obj_list):
#===============================================================================
     '''Read and parse the next line of the file, confirm it matches one of the
        line signatures, such as ('sim_object_type=World', 'size=')

        Parameters: file_object, the input file object.
                    line_number, the current line number being read in.
                    simulation_obj_list, the list of converted lines.
        Returns: False for success, True for failure

        Convert the line in the file to a list of strings, with one string per
            name=value pair (such as "name=Joe").  Make sure that each line matches
            up with one of the line "signatures" in the constant definitions.
            Modify this line_list to only include the value portion of the pair,
            calling extract_line_using_signature (...) to get the each line list.
            Append each modified line_list to the simulation_obj_list( ).

        If success: Return False.
        If failure: Call declare_error (...) and Return True.
    '''
    #List of lists to contain each line of the input file
    line_list = []
    #Read in Lines and append to a list of lines containing strings
    for line in file_object:
        # print(line.strip().split(','))
        line_list.append(line.strip().split())

    #Compare line to signature constants and append to simulation_obj_list
    for i in line_list:
        #World
        if len(i) == NUM_WORLD_TOKENS:
            if i[0].startswith(LINE_SIGNATURE_TUPLE[0][0]) and i[1].startswith(LINE_SIGNATURE_TUPLE[0][1]):
                 simulation_obj_list.append(extract_line_using_signature(LINE_SIGNATURE_TUPLE[0],i))
        #Person
        if len(i) == NUM_PERSON_TOKENS:
            if i[0].startswith(LINE_SIGNATURE_TUPLE[1][0]) and i[1].startswith(LINE_SIGNATURE_TUPLE[1][1]) and \
                i[2].startswith(LINE_SIGNATURE_TUPLE[1][2]):
                    simulation_obj_list.append(extract_line_using_signature(LINE_SIGNATURE_TUPLE[1],i))
        #Robot
        if len(i) == NUM_ROBOT_TOKENS:
            if i[0].startswith(LINE_SIGNATURE_TUPLE[2][0]) and i[1].startswith(LINE_SIGNATURE_TUPLE[2][1]) and \
                i[2].startswith(LINE_SIGNATURE_TUPLE[2][2]) and i[3].startswith(LINE_SIGNATURE_TUPLE[2][3]):
                simulation_obj_list.append(extract_line_using_signature(LINE_SIGNATURE_TUPLE[2],i))

Answer 1

快速丑陋的解决方法是使用elifs 和elses（我假设NUM_WORLD_TOKENS、NUM_PERSON_TOKENS 和NUM_ROBOT_TOKENS 都是唯一值）：

#Compare line to signature constants and append to simulation_obj_list
for i in line_list:
    #World
    if len(i) == NUM_WORLD_TOKENS:
        if i[0].startswith(LINE_SIGNATURE_TUPLE[0][0]) and i[1].startswith(LINE_SIGNATURE_TUPLE[0][1]):
             simulation_obj_list.append(extract_line_using_signature(LINE_SIGNATURE_TUPLE[0],i))
        else:
            declare_error()
            return True
    #Person
    elif len(i) == NUM_PERSON_TOKENS:
        if i[0].startswith(LINE_SIGNATURE_TUPLE[1][0]) and i[1].startswith(LINE_SIGNATURE_TUPLE[1][1]) and \
            i[2].startswith(LINE_SIGNATURE_TUPLE[1][2]):
                simulation_obj_list.append(extract_line_using_signature(LINE_SIGNATURE_TUPLE[1],i))
        else:
            declare_error()
            return True
    #Robot
    elif len(i) == NUM_ROBOT_TOKENS:
        if i[0].startswith(LINE_SIGNATURE_TUPLE[2][0]) and i[1].startswith(LINE_SIGNATURE_TUPLE[2][1]) and \
            i[2].startswith(LINE_SIGNATURE_TUPLE[2][2]) and i[3].startswith(LINE_SIGNATURE_TUPLE[2][3]):
            simulation_obj_list.append(extract_line_using_signature(LINE_SIGNATURE_TUPLE[2],i))
        else:
            declare_error()
            return True

    return False

不过那是很臭的代码。使用正则表达式怎么样？

for line in lines:
    if re.match(WORLD_REGEX, line):
        simulation_obj_list.append(
            extract_line_using_signature(LINE_SIGNATURE_TUPLE[0], line))
    elif re.match(PERSON_REGEX, line):
        # etc

    else:
        declare_error()
        return True

    return False