Learn Python Functions.ipynb

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    "<h1> Learn Python Functions </h1>\n",
    "\n",
    "**April 2021**<br>\n",
    "\n",
    "Instruction, media content, examples and links to resources that will help you build a foundation for Python competency. Jupyter Notebooks are available on [Google Colab](https://colab.research.google.com/drive/1YemG1h8DXENEtITxEmzOF-NDgxbxSB9m?usp=sharing) and [Github](https://github.com/AlphaWaveData/Jupyter-Notebooks/blob/master/Learn%20Python%20Functions.ipynb).\n",
    "\n",
    "<b>Web Resources</b>\n",
    "<br> <a href='https://docs.python.org/3/tutorial/controlflow.html#defining-functions'>Docs.python.org - Functions</a>\n",
    "<br> <a href='https://docs.python.org/3/tutorial/controlflow.html#more-on-defining-functions'>Docs.python.org - More on Functions</a>\n",
    "\n",
    "\n",
    "\n",
    "#### <b>What are Python Functions?</b>\n",
    "\n",
    "A function is a block of organized, reusable code that is used to perform a single, related action. \n",
    "\n",
    "#### <b>Why do we use Functions?</b>\n",
    "\n",
    "Functions provide better modularity for your application and a high degree of code reusing.\n",
    "\n",
    "Python gives you many built-in functions like **print()**, etc. but you can also create your own functions. These functions are called user-defined functions.\n",
    "\n",
    "\n",
    "#### <b>How do we create Functions?</b>\n",
    "\n",
    "You can define functions to provide the required functionality. Here are simple rules to define a function in Python.\n",
    "\n",
    " - Function blocks begin with the keyword **def** followed by the function name and parentheses  ( ) .\n",
    "\n",
    " - Any input parameters or arguments should be placed within these parentheses. You can also define parameters inside these parentheses.\n",
    "\n",
    " - The code block within every function starts after a colon **(:)** and is indented.\n",
    "\n",
    " - The first statement of a function can be an optional statement - the documentation string of the function or docstring.\n",
    "\n",
    " - The statement **return** [expression] exits a function, optionally passing back an expression to the caller. A return statement with no arguments is the same as **return None**. If a **return** statement is not used inside the function, a Python function will also return a 'None' value. This is not equal to zero or nothing, but rather is of type None. A user can check for a None type by using the 'is' operator with 'None' data type: \n",
    "\n",
    "(var1 is None) --> Will return TRUE if var1 is of None data type, otherwise it will return FALSE\n",
    "\n",
    "\n",
    "Here is the syntax of a Function in Python:\n",
    "\n",
    "```python\n",
    "def functionname( parameters ):\n",
    "    \"function_docstring\"\n",
    "    function_suite\n",
    "    return [expression]\n",
    "```\n",
    "\n",
    "By default, parameters have a positional behavior and you need to inform them in the same order that they were defined.\n",
    "\n",
    "Here is an example of a function which takes a string as input parameter and prints it out:\n",
    "\n",
    "```python\n",
    "def printme(str_data):\n",
    "    \"This prints a passed string into this function\"\n",
    "    print(str_data)\n",
    "    return \n",
    "```\n",
    "\n",
    "#### <b>How do we call a Function?</b>\n",
    "\n",
    "Defining a function gives it a name, specifies the parameters that are to be included in the function, and structures the blocks of code. If we name a user-defined function identically to a Python built-in function, Python will default to the user-defined function.\n",
    "\n",
    "Once the basic structure of a function is finalized, you can execute it by calling it from another function or directly from the Python prompt. \n",
    "\n",
    "Here are some examples of calling the function **printme()** defined above:\n",
    "    \n",
    "```python\n",
    "# Now you can call printme function\n",
    "printme(\"I'm the first call to a user defined function!\")\n",
    "printme(\"Again second call to the same function\")\n",
    "```\n",
    "which will produce the following results:\n",
    "    \n",
    "`\n",
    "I'm the first call to a user defined function!\n",
    "Again second call to the same function\n",
    "`\n",
    "\n",
    "#### <b>Where can I find more information on Functions?</b>\n",
    "\n",
    "[Official python documentation on functions](https://docs.python.org/3.7/tutorial/controlflow.html#defining-functions)"
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