python - Python : How to shrink this code? 识别抛出异常的数据

Question

我有一个脚本，它从正在检查不正确数据的记录文件中读入。它们可能各自抛出相同的异常，并且它们存在于同一行。有没有一种方法可以识别哪个字段抛出异常而不必将其分成多行？

此处为玩具示例:

a = [1]
b = [2]
c = [] # Oh no, imagine something happened, like some data entry error
i = 0
try:
    z = a[i] + b[i] + c[i]
except IndexError, e:
    print "Data is missing! %s" % (str(e))

问题是如果出现异常，用户不知道是a、b还是c有数据丢失。

我想我可以这样写:

def check_data(data, index, message):
    try:
        return data[index]
    except IndexError, e:
        print "%s is missing." % (message)
        raise e

a = [1]
b = [2]
c = []
i = 0

try:
    z = check_data(a, i, "a") + check_data(b, i, "b") + check_data(c, i, "c")
except TypeError, e:
    print "Error! We're done."

但这可能非常乏味。

我可以使用哪些其他方法来处理这种情况来验证异常 block 中的每个字段(如果存在)？

下面是根据现实改编的例子:

class Fork:
    def __init__(self, index, fork_name, fork_goal, fork_success):
        # In reality, we would do stuff here.
        pass


forks = []

# In reality, we'd be reading these in and not all of the entries might exist.
fork_names = ["MatrixSpoon", "Spoon", "Spork"]
fork_goals = ["Bend", "Drink soup", "Drink soup but also spear food"]
fork_success = ["Yes!", "Yes!"]

try:
    for i in range(0, len(fork_names)):
        forks.append(Fork(i + 1, fork_names[i], fork_goals[i], fork_success[i]))
except IndexError, e:
    print "There was a problem reading the forks! %s" % (e)
    print "The field that is missing is: %s" % ("?")

Answer 1

您可以将错误检查移动到 Fork 类中并使用 itertools.izip_longest 来确保/something/(实际上是 None)如果一个数据流不足则传入:

class Fork:
    def __init__(self, index, fork_name, fork_goal, fork_success):
        # first, check parameters
        for name, value in (
                ('fork_name', fork_name),
                ('fork_goal', fork_goal),
                ('fork_success', fork_success)
            ):
            if value is None:
                raise ValueError('%s not specified' % name)
        # rest of code

forks = []

# In reality, we'd be reading these in and not all of the entries might exist.
fork_names = ["MatrixSpoon", "Spoon", "Spork"]
fork_goals = ["Bend", "Drink soup", "Drink soup but also spear food"]
fork_success = ["Yes!", "Yes!"]

然后像这样改变你的循环:

for name, goal, sucess in izip_longest(fork_names, fork_goals, fork_success):
    forks.append(Fork(names, goal, success))

现在，您将收到一个错误，清楚地详细说明缺少哪个数据元素。如果您缺少的元素看起来更像 '' 而不是什么都没有，您可以将 __init__ 中的测试从 if value is None 更改为 if不是值。