Python条件赋值运算符 [英] Python conditional assignment operator

问题描述

是否存在与Ruby || = 运算符等效的Python（如果未设置变量则设置变量）？

Does a Python equivalent to the Ruby ||= operator ("set the variable if the variable is not set") exist?

Ruby中的示例：

 variable_not_set ||= 'bla bla'
 variable_not_set == 'bla bla'

 variable_set = 'pi pi'
 variable_set ||= 'bla bla'
 variable_set == 'pi pi'

推荐答案

否，替换为：

try:
   v
except NameError:
   v = 'bla bla'

但是，想要使用此结构表明代码流过于复杂。通常，您会执行以下操作：

However, wanting to use this construct is a sign of overly complicated code flow. Usually, you'd do the following:

try:
   v = complicated()
except ComplicatedError: # complicated failed
   v = 'fallback value'

，并且永远不能确定 v 是否已设置。如果它是可以设置或无法设置的众多选项之一，请使用字典及其 get 方法可使用默认值。

and never be unsure whether v is set or not. If it's one of many options that can either be set or not, use a dictionary and its get method which allows a default value.

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