It shouldn't come as a surprise that Python functions are first-class objects. In Python, function objects have a number of attributes. The reference manual lists a number of special member names that apply to functions. Since functions are objects with attributes, we can extract the docstring or the name of a function, using special attributes such as __doc__ or __name__. We can also extract the body of the function through the __code__ attribute. In compiled languages, this introspection is relatively complex because of the source information that needs to be retained. In Python, it's quite simple.
We can assign functions to variables, pass functions as arguments, and return functions as values. We can easily use these techniques to write higher-order functions.
Additionally, a callable object helps us to create functions. We can consider the callable class definition as a higher-order function. We do need to be judicious in how we use the __init__() method...