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pythondecoratorpython-decorators

Why doesn't this python decorator work?

I'm trying to understand decorators in python. I don't understand why the following doesn't work:

def decorator(func):
    def logger(*args, **kwargs):
        print "start logging"
        func(*args, **kwargs)
        print "end logging"
    return logger

@decorator
def add(a,b):
    return a+b

If I call add(2,3) the output will be:

start logging
end logging

However if I modify my code and write return func(*args, **kwargs) in the definition of logger it works but then end logging is not written on the output.

Solution

  • You can capture the return value in a variable, and return it after printing:

    def decorator(func):
    def logger(*args, **kwargs):
        print "start logging"
        result = func(*args, **kwargs)
        print "end logging"
        return result
    return logger

    Decorators are not special here; it's just a function calling another function.