add lists.md

README.md

@@ -30,6 +30,7 @@ it.**
 5. [Variables, Booleans and None](variables.md)
 6. [Using functions and storing code in files](using-functions.md)
 7. [If, elif, else and while](if.md)
+8. [ThinkPython: Lists](lists.md)
 
 Other things this tutorial comes with:
 

lists.md

@@ -0,0 +1,96 @@
+# ThinkPython: Lists
+
+Now we have learned to save values to variables.
+
+```py
+thing = 'Hello World!'
+```
+
+Then we can do whatever we want with the variable.
+
+```py
+print(thing)
+```
+
+But what if you have a lot of values? You can just make a lot of
+variables...
+
+```py
+thing1 = 'Hello World!'
+thing2 = 'hi'
+thing3 = 123
+thing4 = 3.14
+thing5 = 42
+thing6 = 'This is yet another thing.'
+thing7 = 'Python is fun!'
+
+print(thing1)
+print(thing2)
+print(thing3)
+print(thing4)
+print(thing5)
+print(thing6)
+print(thing7)
+```
+
+...or you can use a list and keep everything in one variable.
+
+```py
+things = ['Hello World!', 'hi', 123, 3.14, 42,
+          'This is yet another thing.', 'Python is fun!']
+for thing in things:
+    print(thing)
+```
+
+[Read more about lists in ThinkPython
+here.](http://greenteapress.com/thinkpython2/html/thinkpython2011.html)
+Skip the chapter "10.7 Map, filter and reduce" and the excercises. You
+would need to know how to define functions using the `def` keyword, but
+we haven't talked about that yet.
+
+## Summary
+
+- Lists are a way to store multiple values in one variable. We can
+    create lists by putting whatever we want inside [square brackets],
+    for example, `our_list = []` creates an empty list.
+- Never do `list = ...`. `list` is a built-in class, and it's used for
+    converting other values to lists, like `list_of_thingy = list(thingy)`.
+    If we do `list = something`, then `list(thingy)` will probably do
+    something else than we want it to do.
+- When we have created a list, we can slice it. For example,
+    `our_list[2:]` results in a new list with everything in the
+    original list except the first two elements. Negative indexes start
+    from the end of the list, for example, `our_list[-2:]` is a list of
+    the last two elements.
+- We can also index lists, `our_list[0]` is the first element in the
+    list. Non-negative indexes start at zero, and negative indexes
+    start at -1.
+- You can assign to indexes and slices like `some_list[0] = 'hi'`, or
+    delete them like `del some_list[:2]`.
+- `a = b` does not create a copy of b.
+
+    ```py
+    >>> a = []
+    >>> b = a            # this does not copy anything
+    >>> b += [1, 2, 3]
+    >>> a
+    [1, 2, 3]
+    >>> 
+    ```
+
+    If you want a copy, use the `.copy()` list method:
+
+    ```py
+    >>> a = []
+    >>> b = a.copy()
+    >>> b += [1, 2, 3]
+    >>> a
+    []
+    >>> 
+    ```
+
+***
+
+You may use this tutorial freely at your own risk. See [LICENSE](LICENSE).
+
+[Back to the list of contents](README.md)