是否存在用于变量检查和赋值的Python快捷方式? [英] Is there a Python shortcut for variable checking and assignment?

问题描述

我发现自己经常键入以下内容(如果相关的话，请为Django开发):

I'm finding myself typing the following a lot (developing for Django, if that's relevant):

if testVariable then:
   myVariable = testVariable
else:
   # something else

或者更常见的方式(即建立参数列表)

Alternatively, and more commonly (i.e. building up a parameters list)

if 'query' in request.POST.keys() then:
   myVariable = request.POST['query']
else:
   # something else, probably looking at other keys

是否有我不知道的快捷方式可以简化此操作?带有某种逻辑 myVariable = Assign_if_exists(testVariable)?

Is there a shortcut I just don't know about that simplifies this? Something with the kind of logic myVariable = assign_if_exists(testVariable)?

推荐答案

假设您希望在不存在"的情况下将myVariable保持其先前值不变，

Assuming you want to leave myVariable untouched to its previous value in the "not exist" case,

myVariable = testVariable or myVariable

处理第一种情况，

myVariable = request.POST.get('query', myVariable)

与第二个交易.不过，两者都与"exist"无关(这几乎不是Python的概念；-):第一个与true或false有关，第二个与集合中是否存在键有关.

deals with the second one. Neither has much to do with "exist", though (which is hardly a Python concept;-): the first one is about true or false, the second one about presence or absence of a key in a collection.

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