How to Determine if a Variable is a Function in Python?

Checking if a Variable is a Function

To ascertain whether a variable references a function, Python offers several approaches.

Callable Function

For Python 2.x and Python 3.2 , the callable() function can be employed:

<code class="python">callable(obj)</code>

call Attribute

In Python 3.x prior to 3.2, check if the object possesses a call attribute:

<code class="python">hasattr(obj, '__call__')</code>

Caveats of Other Methods

Using types.FunctionTypes or inspect.isfunction, which essentially perform the same task, carries certain caveats. These approaches yield False for non-Python functions, including most builtins implemented in C:

<code class="python">>>> isinstance(open, types.FunctionType)
False
>>> callable(open)
True</code>

Therefore, it's advisable to use callable() or hasattr() to ascertain the presence of the call attribute, effectively determining whether an object can be called as a function.

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