Add lesson 4 notebooks

Author: davewhipp

notebooks/L4/functions.ipynb

@@ -0,0 +1,227 @@
+{
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+    "# Loading and using modules\n",
+    "\n",
+    "## What is a module?\n",
+    "\n",
+    "A *module* in Python is simply a Python `.py` file that contains a list of related functions that can be loaded and used.\n",
+    "Modules are similar to what are more generally called libraries in programming languages, which again contain code related to a specific task such as mathematical operations.\n",
+    "There are a *HUGE* number of Python modules, and many of them greatly extend what can be done in a normal Python program.\n",
+    "In fact, the abundance of free Python modules is one of the best reasons to learn and start using Python.\n",
+    "\n",
+    "## How can modules be loaded?\n",
+    "\n",
+    "Python modules can be loaded in a number of different ways.\n",
+    "\n",
+    "### Loading a module\n",
+    "    \n",
+    "Let's start simple with the math module.\n",
+    "Here, we’ll load the math module using the `import` statement."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
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+   "source": [
+    "Here we have loaded the math module by typing `import math`, which tells Python to read in the functions in the math module and make them available for use.\n",
+    "In our example, we see that we can use a function within the math library by typing the name of the module first, a period, and then the name of function we would like to use afterward (e.g., `math.sqrt()`).\n",
+    "Built-in functions such as `print()` do not require the name of the module first since nothing is explicitly imported.\n",
+    "\n",
+    "### Renaming imported modules\n",
+    "\n",
+    "We can also rename modules when they are imported.\n",
+    "This can be helpful when using modules with longer names."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
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+   "metadata": {},
+   "source": [
+    "In this example we now see that when the math module is imported, it is imported to be usable with the name `m` instead of `math`.\n",
+    "It doesn't matter much in our toy example here since math is not a long module name, but we will see other examples later in the course where renaming the modules is very helpful (e.g., matplotlib).\n",
+    "\n",
+    "### Importing a single function\n",
+    "\n",
+    "It is also possible to import only a single function from a module, rather than the entire module.\n",
+    "This is sometimes useful when using large modules that have much more available than the desired use."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
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+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Though this can be useful, it has the drawback that the imported function could conflict with other built-in or imported function names, and you lose the information about which module contains the function.\n",
+    "You should only do this when you truly need to.\n",
+    "\n",
+    "### Importing part of a module\n",
+    "\n",
+    "Some modules have sub-modules that can also be imported without importing the entire module.\n",
+    "We may see examples of this later when making data plots using the pyplot sub-module of the [Matplotlib module](http://matplotlib.org/).\n",
+    "In case you're curious, here is an example."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
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+   "cell_type": "code",
+   "execution_count": null,
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+   "outputs": [],
+   "source": []
+  },
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+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "This creates a new figure window for a pyplot figure.\n",
+    "Again, we'll see how this works and what it means later in the course."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## How can modules be used?\n",
+    "\n",
+    "As we see above, the easiest way to use a module is to import it an then use its functions by typing `modulename.functionname()` and providing the necessary arguments.\n",
+    "Yes, it is that simple.\n",
+    "\n",
+    "However, there are times you may not know the names of all of the functions in a given module, or which are part of a module.\n",
+    "You can view the list of functions that are part of a module by using the `dir()` function."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "So that's helpful, but what about when you don't know what a given function does?\n",
+    "The easiest solution is to use the `help()` function."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "Note that you'll need to press `q` to exit the help viewer."
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## What should I not do?\n",
+    "\n",
+    "Here are a few things to avoid.\n",
+    "\n",
+    "### from X import *\n",
+    "\n",
+    "Don't use `from X import *`.\n",
+    "This may be easier to understand by way of an example, but assuming `X` above is a Python module, `from X import *` will import all of the functions in module X.\n",
+    "Though you might think this is helpful, it is much better to simply `import X` or `import X as Y` to keep the connection between the functions and their module.\n",
+    "It is also much more likely you will encounter conflicting names when using `from X import *`.\n",
+    "\n",
+    "### Poor names when renaming on import\n",
+    "\n",
+    "Don't use confusing names when renaming on import.\n",
+    "Be smart when you import modules.\n",
+    "If you want to make the module name shorter on import, pick a reasonable abbreviation.\n",
+    "For instance, `import matplotlib as m` could be confusing, especially if you're also using `import math as m` in other Jupyter notebooks or script files.\n",
+    "Similarly, `import matplotlib as math` is perfectly OK syntax in Python, but bound to cause a world of trouble.\n",
+    "Remember, people need to be able to read and understand the code you write, keep it simple and logical."
+   ]
+  }
+ ],
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