在Python中，如何检查变量是否存在？
如果“x”存在，则打印“x存在”。
我问这个是因为我总是收到此错误：
UnboundLocalError at /settings/
local variable 'avatarlink' referenced before assignment
If "x" exists, then print "x exists".
I ask this because I always get this error:
UnboundLocalError at /settings/
local variable 'avatarlink' referenced before assignment
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为什么你需要知道？如果代码因此而中断，则可能是因为代码无论如何都是错误的并且需要修复。
也就是说，请尝试检查
if 'x' in locals()或if 'x' in globals()，根据您的预期情况进行检查。Why do you need to know? If the code breaks because of this, it's probably because the code is wrong anyway and needs to be fixed.
That said, try checking
if 'x' in locals()orif 'x' in globals(), as appropriate to where you're expecting it to be.正如 Python 中所说，“请求宽恕比请求许可更好”。因此，只需尝试访问该变量，如果它不存在，则捕获错误。
但是，我真的很想知道为什么您认为需要这样做。通常，您总是会在检查变量的值之前设置该变量。
As they say in Python, "it's better to ask forgiveness than permission". So, just try and access the variable, and catch the error if it doesn't exist.
However, I would really like to know why you think you need to do this. Usually, you would always set the variable before checking its value.
您可以检查 x 是否在
globals()或locals()中。You may check if x is in
globals()orlocals().在 python 中，你确实不应该使用尚未设置的变量。如果需要，您可以将 avatarLink 设置为 None。
In python you really shouldn't be using variables which haven't been set. If need be you can set avatarLink to None.