python - Python - 嵌套 if 的相同 else 代码

Question

在 Django 中，处理表单的规范方式是：

if request.method == 'POST':
    form = SomeForm(request.POST)
    if form.is_valid():
        use the form data

无论没有 POST 还是表单无效，我都想执行相同的代码 - 这是几行代码，所以我想知道是否有比两个重复的 else 块更好的方法（一个用于内部if 和一个用于外部）？

Answer 1

使用单独的函数：

if request.method != 'POST':
    return do_something_function_for_invalid(request)

form = SomeForm(request.POST)
if not form.is_valid():
    return do_something_function_for_invalid(request)

# do something

然后定义do_something_function_for_invalid()为：

def do_something_function_for_invalid(request):
    # do something

    return response

或者，使用异常处理：

try:
    if request.method != 'POST':
        raise ValueError('invalid form')

    form = SomeForm(request.POST)
    if not form.is_valid():
        raise ValueError('not a POST request')

     # do something
except ValueError as ve:
    # handle ve exception, ve.args[0] is the error message

Answer 2

A very concise way that does not require a separate function, and doesn't repeat conditions:

form = SomeForm(request.POST) if request.method == 'POST' else None

if form and form.is_valid():
    # do your valid-submission stuff
else:
    # do your invalid-submission stuff

Answer 3

简单到

if (request.method != 'POST') or (not SomeForm(request.POST).is_valid()):
   do something