isinstance 不导入候选人

Question

We have a function which takes a variety of different types of input: a function, a string, a compiled regular expression, a Hamcrest Matcher<\/a> , and filters a list appropriately based on the type of the input.

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Answer 1

恕我直言，使用type(POSSIBLE_MATCHER).__name__是一种相当优雅的类型检查解决方案，而无需导入模块。

Answer 2

If you want to cater for inheritance, using type(POSSIBLE_MATCHER).__name__ will not cut it. You could then check against all types in the inheritance chain:

class_string in [t.__name__ for t in type(POSSIBLE_MATCHER).__mro__]

Answer 3

even though this is a quite old question, I thought I'll share my solution for this:

• use a conditional import and set a flag to check if the import was successful before isinstance() ! (after all if the module cannot be imported isinstance should always return False )

eg something like this:

try:
    import somemodule

    _import_OK = True
except ImportError:
    _import_OK = False


# and then later in the code:
if _import_OK:
    q = isinstance(x, somemodule.something)
else
    q = False