starts completing doc and adds gitignore

.gitignore

@@ -0,0 +1,3 @@
+*.pdf
+*.docx
+.~lock*

learning_python3.md

@@ -16,8 +16,12 @@ Below is a small overview of how I would subdivide them.
 
 The subtopics behind the concept of programming can be sliced (in no particular order) as follows:
 
-* objects
+* objects or **OOP** (Object Orientated Programming)
-* variables
+	* abstraction
+	* encapsulation
+	* inheritance
+	* polymorphism
+* variables (which are **not** *boxes* in python3)
 * conditional logic
 * functions
 * loops
@@ -71,7 +75,33 @@ TODO
 
 # Your first project
 
-TODO helloworld
+In almost any language you'll find a *helloworld* program.
+It serves to illustrate a *very* basic working script or program to showcase the syntax.
+In python a helloworld is done as such.
+
+```python3
+print("Hello World!")
+```
+
+Just for reference below are a few helloworld programs in different languages.
+First `c#` then `c` and last but not least `javascript`.
+
+```c#
+Console.WriteLine("Hello World!");
+```
+
+```c
+#include <stdio.h>
+
+int main() {
+   printf("Hello World!");
+   return 0;
+}
+```
+
+```javascript
+alert( 'Hello, world!' );
+```
 
 ## How to execute
 
@@ -80,16 +110,96 @@ TODO helloworld
 
 ## Simple printing
 
-## String formatting
+The most basic printing can be done by calling the `print` function.
+In python a call is symbolized by the `()`.
+In practice this becomes as follows.
+
+```python3
+print("hello world")
+print("my name is Wouter")
+print("I'm", 35, "years old")
+```
+
+__🏃 Try it__
+
+Try printing different lines and with combinations of different object types such as `int`, `float` and `str`.
+What happens if you *add* (`+`) values to one another?
+
+
+We can also print the objects referenced by variables.
+A simple example:
+
+```python3
+name = "Wouter"
+age = "35"
+
+print("Hello, my name is", name, "and I'm", age, "years old.")
+```
+
+While it works perfectly well it's not super *readable*.
+We can improve the readability by using either string replacement or string formatting.
+My personal preference is string formatting.
+
+__🏃 Try it__
+
+Have a look at both ways illustrated below and try them out.
+
 
 ## String replacement
 
+```python3
+name = "Wouter"
+age = "35"
+
+print("Hello, my name is {name} and I'm {age} years old.")
+```
+
+## String formatting
+
+```python3
+name = "Wouter"
+age = "35"
+
+print("Hello, my name is {} and I'm {} years old.".format(name, age))
+```
+
+## Some links to read up
+
+* [realpython string formatting](https://realpython.com/python-string-formatting/)
+
 # Taking input
 
-TODO say hello program
+The first **builtin function** we saw is `print` which can be used to signal messages to the user.
+But how can we **get** some information from the user?
+This is done with the `input` function.
+If we open up a python shell we can observe it's behaviour.
+
+```python3
+>>> input()
+hello world
+'hello world'
+>>> 
+```
+
+It seems to echo back what we type on the empty line.
+If we take this idea and add it to a script the behaviour changes slightly.
+The [prompt](https://en.wikipedia.org/wiki/Command-line_interface#Command_prompt) appears but when we hit `enter` the text is not printed.
+This is one of the slight nuances between running scripts and using the shell.
+The shell is more *verbose* and will explicitly tell you what a function returns, unless it doesn't return anything.
 
 ## Functions can return something
 
+So, functions can **return** something but how can we *use* the returned objects?
+This is where **variables** come in handy.
+
+```python3
+print("What is your name? ")
+answer = input()
+print("Well hello", answer, "!")
+```
+
+## Functions can take arguments
+
 # Taking input and evaluation
 
 TODO say hello plus ask for age