Python 字符串转 Int 或 None
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Python String to Int Or None
提问by user2686811
Learning Python and a little bit stuck.
学习Python，有点卡住了。
I'm trying to set a variable to equal int(stringToInt)or if the string is empty set to None.
我正在尝试将一个变量设置为等于，int(stringToInt)或者如果字符串为空设置为None.
I tried to do variable = int(stringToInt) or Nonebut if the string is empty it will error instead of just setting it to None.
我尝试这样做，variable = int(stringToInt) or None但如果字符串为空，它将出错，而不仅仅是将其设置为 None。
Do you know any way around this?
你知道有什么办法解决这个问题吗？
采纳答案by That1Guy
If you want a one-liner like you've attempted, go with this:
如果您想要像您尝试过的单线，请使用以下方法：
variable = int(stringToInt) if stringToInt else None
This will assign variableto int(stringToInt)only if is not empty AND is "numeric". If, for example stringToIntis 'mystring', a ValueErrorwill be raised.
仅当不为空且为“数字”时才会分配variable给int(stringToInt)。例如，如果stringToInt是'mystring'，aValueError将被引发。
To avoid ValueErrors, so long as you're not making a generator expression, use a try-except:
为了避免ValueErrors，只要您不创建生成器表达式，请使用 try-except：
try:
variable = int(stringToInt)
except ValueError:
variable = None
回答by Rob?
Use the fact that it generates an exception:
使用它生成异常的事实：
try:
variable = int(stringToInt)
except ValueError:
variable = None
This has the pleasant side-effect of binding variableto Nonefor other common errors: stringToInt='ZZTop', for example.
这具有绑定variable到None其他常见错误的令人愉快的副作用：stringToInt='ZZTop'例如。
回答by Brian Cain
Here are some options:
以下是一些选项：
Catch the exception and handle it:
捕获异常并处理它：
try:
variable = int(stringToInt)
except ValueError, e:
variable = None
It's not really that exceptional, account for it:
这并不是那么特殊，请解释一下：
variable = None
if not stringToInt.isdigit():
variable = int(stringtoInt)
回答by moliware
I think this is the clearest way:
我认为这是最清晰的方法：
variable = int(stringToInt) if stringToInt.isdigit() else None
