[Decorators function] #builtin #python

Standard - Decorators nested function calling.ipynb

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      "source": "# Decorators \nA decorator is any callable Python object that is used to modify a function, method or class definition. A decorator is passed the original object being defined and returns a modified object, which is then bound to the name in the definition. Python decorators were inspired in part by Java annotations, and have a similar syntax; the decorator syntax is pure syntactic sugar, using @ as the keyword."
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      "cell_type": "markdown",
      "source": "# Use Cases"
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      "source": "Decorators are python synati csugar for embeddeding functions within functions to make it easier to maintain (i.e. scalable and a single place to edit) common features shared across code. \n\nA practical example is [debug logger](https://gist.github.com/dabbe2a5432cb4083c51ffea8d71eab7)\n"
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      "source": "## Step 1 - Declare the decorator function"
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      "source": "def logger(func):\n    \"\"\"\n    :return: func\n    \"\"\"\n    print('logger added to func:{}'.format(func.__name__))\n\n    def wrapper(*args, **kwargs):\n        print('calling: {}'.format(func.__name__))\n        return func(*args, **kwargs)\n    return wrapper\n\n\n",
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      "source": "## Step 2 - Bind the decorator the  function\nThe print_hello_world function is modified in order to bind append the logger function when called. \n\nAt this point, the logger function is called, passing the print_hello_world. The logger function will then execute all code (including the def line only) except the return keyword, resulting in the print statement to be sent to the console i.e. 'logger added to func'"
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      "source": "@logger\ndef print_hello_world(x, y):\n    print('x:{}, y:{}'.format(x, y))\n",
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      "outputs": [
        {
          "output_type": "stream",
          "text": "logger added to func:print_hello_world\n",
          "name": "stdout"
        }
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      "source": "print_hello_world(x='karl', y = 'beigan')",
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          "text": "calling: print_hello_world\nx:karl, y:beigan\n",
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