如何检查请求.GET var是None？ [英] How to Check if request.GET var is None?

问题描述

我正在进入django，这让我头疼。
我试图获得一个简单的GET变量。网址是site.com/search/?q=search-term

我的观点是：

  def search（request）：
 if request.method =='GET'and'q'in request.GET：
q = request.GET.get（'q'没有）
如果q不是None：
 results = Task.objects.filter（
 Q（title__contains = q）
 | 
 Q（description__contains = q） 
）
 ... return ... 
 else：
 ... 
 else：
 ... 
  

搜索查询，如： mysite.com/search/？ （没有q）如果正确地通过第一个。

问题出在诸如 mysite.com/search/?q = 。如果q不是没有，它们不会被所捕获：

所以，简短的答案将是如何检查q ==' ？ （我已经尝试过，没有，等等，没有用。）

解决方案

首先，检查 request.GET dict包含一个名为 q 的参数。你正在这样做：

  if request.method =='GET'and'q'in request.GET： 
  

接下来，检查 q 是无或空字符串。为此，您可以这样写：

  q = request.GET ['q'] 
如果q是不是无和q！=''：
＃在这里处理
  

请注意，不需要写 request.GET.get（'q'，None）。我们已经检查过，确保 request.GET dict中有一个'q'键，所以我们可以直接获取价值。你应该使用 get 方法的唯一时间是，如果你不确定一个dict有一定的密钥，并且想要避免引发一个KeyError异常。

但是，根据以下事实，有一个更好的解决方案：

• 值无评估为 False


• 空字符串 / code>还会评估为 False


• 任何非空字符串的计算结果为 True 。



所以现在你可以写：

  q = request.GET ['q'] 
如果q：
＃在这里处理
  

查看这些其他资源了解更多详情：

• Python：真值测试


• Python： dict.get

Hey, I'm getting into django and this is getting me a headache. I'm trying to get a simple GET variable. URL is site.com/search/?q=search-term

My view is:

def search(request):
if request.method == 'GET' and 'q' in request.GET:
    q = request.GET.get('q', None)
    if q is not None:
        results = Task.objects.filter(
                               Q(title__contains=q)
                               |
                               Q(description__contains=q),
                               )
        ...return...
    else:
        ...
else:
    ...

Search queries like: mysite.com/search/? (without q) gets through the first if correctly.

The problem is in queries like mysite.com/search/?q=. They don't get caught by if q is not None:

So, the short answer would be How can I check q == ''? (I've already tried '', None, etc, to no avail.)

解决方案

First, check if the request.GET dict contains a parameter named q. You're doing this properly already:

if request.method == 'GET' and 'q' in request.GET:

Next, check if the value of q is either None or the empty string. To do that, you can write this:

q = request.GET['q']
if q is not None and q != '':
    # Do processing here

Notice that it is not necessary to write request.GET.get('q', None). We've already checked to make sure there is a 'q' key inside the request.GET dict, so we can grab the value directly. The only time you should use the get method is if you're not sure a dict has a certain key and want to avoid raising a KeyError exception.

However, there is an even better solution based on the following facts:

• The value None evaluates to False
• The empty string '' also evaluates to False
• Any non-empty string evaluates to True.

So now you can write:

q = request.GET['q']
if q:
    # Do processing here

See these other resources for more details:

• Python: Truth Value Testing
• Python: dict.get

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