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pythonpython-decorators

How Python script executes?

I have a following small Python program:

def wrap(func):
    print "before execution ..."
    a = func()
    print "after execution ..."
    return a


@wrap
def dosomething():
    print "doing something ..."

When I execute above script I should not get any output as I am not calling:

dosomething()

But when I execute this script I get the following output:

before execution ...
doing something ...
after execution ...

Please explain the reason for this behavior

Solution

  • A decorator is just a callable that takes a function as an argument and returns a replacement function. We’ll start simply and work our way up to useful decorators.

    The @ symbol applies a decorator to a function so it's equal to:

    dosomething = wrap(dosomething)

    Which runs wrap. and prints the output.

    Here's some info about decorators: https://wiki.python.org/moin/PythonDecorators

    http://simeonfranklin.com/blog/2012/jul/1/python-decorators-in-12-steps/