Question

我的代码工作正常，但PyCharm警告以下except条款过于宽泛。老实说，它也让我觉得这是错误的实施。

在批量抓取HTML <tr>时，我还必须添加到数据库或更新，我事先不知道游戏是否完成。此外，尚未完成的游戏在某些<td>中有不同的HTML标记，需要不同的处理。

基本上，如果我们查看match_score_string和match_relevant_bit，我们会告诉BeautifulSoup查找具有特定类别的<td>。如果游戏已经完成，则此<td>将有一个score-time sc课程，如果没有，则会有一个score-time st课程。如果它有一个，它就不会拥有另一个。

自从我编写try-except条款以来已经有一段时间了，但如果我没记错的话，原因（我觉得）我必须使用它们是因为BS会抛出错误并停止所有操作当row.find无法找到HTML对象时。

PyCharm是否有理由抱怨？

# Get Match Score
try:
    match_score_string = row.find("td", class_="score-time sc").get_text()
    match_string_split = match_score_string.split(" - ")
    team_a_score = int(match_string_split[0])
    team_b_score = int(match_string_split[1])
    print(team_a_score)
    print(team_b_score)
except:
    team_a_score = None
    team_b_score = None

# Get Match URL
try:
   match_relevant_bit = row.find("td", class_="score-time sc")
   match_url = match_relevant_bit.find("a").get("href")
   match_url_done = match_url.rsplit('?JKLMN')
   match_url = match_url_done[0]
   match_finished = True

except:

   match_relevant_bit = row.find("td", class_="score-time st")
   match_url = match_relevant_bit.find("a").get("href")
   match_url_done = match_url.rsplit('?JKLMN')
   match_url = match_url_done[0]
   match_finished = False

Answer 1

您的except肯定过于宽泛。在这些情况下，我不确定是否需要异常处理，我不会提出异议 - 例外是相当pythonic所以在你觉得合适的地方使用它们。但是，您还没有争辩说您需要使用代码来处理可以想象的每个异常。裸露的除外可以掩盖各种各样的错误。例如如果您在以后的版本中拼错变量名称：

try:
    match_score_string = row.find("td", class_="score-time sc").get_text()
    match_string_split = match_score_string.split(" - ")
    team_a_score = int(match_string_spilt[0])  # oops
    team_b_score = int(match_string_split[1])
    print(team_a_score)
    print(team_b_score)
except:
    team_a_score = None
    team_b_score = None

裸露的例外也会阻止用户发送KeyboardInterrupt来终止该程序......

这只是两个例子，为什么你不想要一个裸露的 - 除了可以被这掩盖的编程错误的数量接近无限，我没有足够的时间来证明所有的他们; - ）。

相反，您应该准确指定您希望遇到的异常：

try:
    match_score_string = row.find("td", class_="score-time sc").get_text()
    match_string_split = match_score_string.split(" - ")
    team_a_score = int(match_string_spilt[0])  # oops
    team_b_score = int(match_string_split[1])
    print(team_a_score)
    print(team_b_score)
except AttributeError:  # If no row is found, accessing get_text fails.
    team_a_score = None
    team_b_score = None

这样，代码就像你期望的那样执行和你不会掩盖（太多）编程错误。为防止隐藏错误，您要做的下一步是尽可能地限制异常处理程序中的代码量。

Answer 2

尝试/除外条款很棒。听起来你不经常使用它们。

try/except块可以帮助您避免复杂的if语句，或者在继续之前检查条件的代码，这有时会使您不清楚自己尝试要做什么（请参阅我的内容）在那里：P）。

有一些例外情况可能会拖出您的代码，其中一些可能比其他代码更有可能。见下文：

try:
    # This first line could have an AttributeError in two places
    #     Maybe the row didn't parse quite correctly? find() won't work then.
    #     Maybe you didn't find any elements? get_text() won't work then.
    match_score_string = row.find("td", class_="score-time sc").get_text()
                            ^                                  ^
    # Same as here, you could get an AttributeError if match_score_string isn't a string.
    #     I would say that isn't very likely in this case,
    #     Especially if you handle the above line safely.
    match_string_split = match_score_string.split(" - ")

    # If either of these split strings contains no matches, you'll get an IndexError
    # If either of the strings at the index contain letters, you may get a ValueError
    team_a_score = int(match_string_split[0])
    team_b_score = int(match_string_split[1])

    # Theoretically, if you caught the exception from the above two lines
    #     you might get a NameError here, if the variables above never ended up being defined.
    print(team_a_score)
    print(team_b_score)
except:
    # Can't really imagine much going wrong here though.
    team_a_score = None
    team_b_score = None

正如您可能想象的那样，捕获几种类型的异常可能更有用。这取决于您输入的复杂程度。

多个try / except块在这里也是有益的，特别是为了处理你捕获错误并需要继续执行该块中其余代码的情况。

Python：我的except子句确实太宽泛了吗？

2 个答案: