adds functions

learning_python3.md

@@ -307,6 +307,8 @@ else:
 	print("you are at a dangerous crossroad in life!")
 ```
 
+⛑ **Do not fight the automatic indentation in your IDE! Pycharm is intelligent enough to know when to indent so if it does not indent by itself, you probably made a syntax error.**
+
 ## Class string methods
 
 Let's take the logic above and implement it in a real program.
@@ -423,10 +425,12 @@ else:
 We can use conditional logic to create quite elaborate decision processes.
 Let's build a mini text based adventure game.
 Granted it's not a *tripple A* game but it will train your `if` and `else` skills plus it will highlight some issues we'll overcome in the next section.
-Consider the diagram below.
 
 ![adventure game](./assets/text_based_adventure_game.png)
 
+Consider the diagram above we can imagine a program that functions nicely with the code below.
+It is not very *readable* nor *scalable*.
+
 ```python3
 answer = input("You're at a cross section. Do you go left or right?")
 if answer.startswith("l"):
@@ -475,12 +479,108 @@ else:
     exit(0)
 ```
 
+I urge you to read up on some [best practices](https://www.tutorialdocs.com/article/python-conditional-statements-tips.html) for `if` statements.
+We will not improve on this particular example but I do advise you to create a similar style game during one of the workshops once we have learned some new tricks.
+
 # Creating your own functions 
 
+One of the *issues* we have in the text based game example is duplicate code.
+At two spots we execute almost identical code and this is something that should be avoided at all costs!
+Why write the same thing over and over?
+You're better off writing it **once** and use it **lots**.
+This is where **functions** come into play.
+
+Python ships with a lot of built-in functions but we can create our own very easily.
+The keyword to define a function in python is `def`.
+All the code that is *indented* will be executed when we **call** the function.
+Here is a basic abstraction of correct syntax.
+
+```python3
+def first_function():
+	print("I'm a function")
+	print("Hear me roar!")
+```
+
+If you type *only* the code above in a new script, and run it, you won't see much.
+This is because you only **created** the function.
+To use it you need to **call** it.
+This is done as follows.
+
+```python3
+def first_function():
+	print("I'm a function")
+	print("Hear me roar!")
+
+first_function()
+```
+
+Learning how to create functions is a big step in your programming journey.
+It can seem confusing at first because the code execution *appears* to jump around.
+This is however **not** the case.
+Your script is still read and executed **line by line** so you can not call a function **before** you defined it!
+For now you should not overthink the structure of you scripts.
+As long as they work you should be happy.
+We'll dive into the proper *anatomy* of a program real soon.
+
 ## Functions that *do* something
 
-TODO recipe with variable flavor (chocolate, vanilla, ...)
-TODO pretty_print
+The first function I showed you above performs a series of actions each time it is called.
+We can use it to *bake cakes* for example.
+Below we create **one** function to bake the cake, and call it **three** times to bake three cakes.
+
+```python3
+def bake_chocolate_cake():
+	print("mix the base ingredients")
+	print("add the chocolate flavour")
+	print("put in the oven")
+	print("enjoy!")
+
+bake_chocolate_cake()
+bake_chocolate_cake()
+bake_chocolate_cake()
+```
+
+Now, you might like a *vanilla* cake from time to time.
+Easy, we'll just write a second function for that purpose.
+
+```python3
+def bake_chocolate_cake():
+	print("mix the base ingredients")
+	print("add the chocolate flavour")
+	print("put in the oven")
+	print("enjoy!")
+
+def bake_vanilla_cake():
+	print("mix the base ingredients")
+	print("add the vanilla flavour")
+	print("put in the oven")
+	print("enjoy!")
+
+bake_chocolate_cake()
+bake_chocolate_cake()
+bake_vanilla_cake()
+bake_chocolate_cake()
+bake_vanilla_cake()
+```
+
+Voila, we can now make as many chocolate and vanilla cakes as we want!
+But what about *bananas*?
+Following our logic we can create a *third* function to bake a banana cake but you're probably seeing a *pattern* here.
+Each `bake_FLAVOR_cake` function is almost identical, just for the flavoring.
+We can create one generic `bake_cake` function and just add the custom flavor each time we actually *bake* a cake.
+This is done with arguments.
+
+```python3
+def bake_cake(flavor):
+	print("mix the base ingredients")
+	print("add the {} flavor".format(flavor))
+	print("put in the oven")
+	print("enjoy!")
+
+bake_cake("chocolate")
+bake_cake("vanilla")
+bake_cake("banana")
+```
 
 ## Variable scope
 
@@ -488,6 +588,43 @@ TODO pretty_print
 
 TODO basic math functions
 
+## Some links to read up on
+
+* some [best practices](https://able.bio/rhett/python-functions-and-best-practices--78aclaa) for functions
+* more details on [variable scope](https://pythongeeks.org/python-variable-scope/)
+
+# Coding challenge - Pretty Print
+
+Can you write me a function that decorates a name or message with a *pretty* character.
+Kind of like the two examples below.
+
+```
+##########
+# Wouter #
+##########
+
+#################
+# Python rules! #
+#################
+```
+
+<details>
+  <summary>Spoiler warning</summary>
+
+```python3
+def pretty_print(msg, decorator="#"):
+	line_len = len(msg) + (len(decorator) * 2) + 2
+	print(decorator * line_len)
+	print("{} {} {}".format(decorator, msg, decorator))
+	print(decorator * line_len)
+
+pretty_print("Wouter")
+pretty_print("Python rules!")
+pretty_print("Alice", "-")
+```
+
+</details>
+
 # Using the standard library
 
 TODO import random exercise (digital dice)