clean up nested list chapter

Author: Kristian Rother

first_steps/nested_lists.rst

@@ -0,0 +1,99 @@
+Nested Lists
+============
+
+In this chapter you learn:
+--------------------------
+
+==== ==============================================
+area topic
+==== ==============================================
+⚙    define a list inside a list
+⚙    index a nested list
+🔀   loop over a nested list
+🔀   create a nested list with a nested loop
+==== ==============================================
+
+Data frequently occurs in the form of tables. To process tables in
+Python, we can put lists in other lists. These are called **nested lists**:
+
+.. code:: python3
+
+   table = [
+     ["Emma", 20799],
+     ["Olivia", 19674],
+     ["Sophia", 18490],
+     ["Isabella", 16950],
+     ["Ava", 15586],
+     ["Mia", 13442],
+     ["Emily", 12562],
+   ]
+
+Generally, for nested lists, the same rules apply as for single lists.
+E.g. for the third row:
+
+.. code:: python3
+
+   print(table[2])
+  
+To access a single element, you need two pairs of square brackets.
+E.g. for the second column of the third row:
+
+.. code:: python3
+
+   print(table[2][1])
+
+In this chapter we will create and process nested lists.
+
+
+Exercise 1
+----------
+
+Write all rows of the above table to the screen with a ``for`` loop.
+
+Complete the code:
+
+.. code:: python3
+
+   for ... in table:
+       print(...):
+
+
+Exercise 2
+----------
+
+Now modify the loop to output only the names.
+
+
+Exercise 3
+----------
+
+Write each individual *cell* of the table to the screen with a nested ``for`` loop.
+
+Complete the code:
+
+.. code:: python3
+
+   for row in ...:
+       ... cell in row:
+           print(...)
+
+
+Exercise 4
+----------
+
+Create an empty table of 10 x 10 cells and fill them with numbers from 1
+to 100.
+
+Sort the lines and indent the code properly:
+
+.. code:: python3
+
+   for x in range(10):
+   for y in range(10):
+   number = 1
+   number += 1
+   print(table)
+   row = []
+   row.append(number)
+   table.append(row)
+   table = []