Koans (Optional)

Koans are puzzles or exercises that are a great way to reinforce your learnings of a programming language’s constructs.

Find instructions on how to download and run them below.

Making assertions

The koans use the keyword assert a lot. When you assert something you are stating that it must be true.

In python true and false are represented by the keywords True and False.

assert passes silently when it is followed by True but throws an Error when followed by False:

>>> assert True
>>> assert False
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>

In the Koans you have to find answers that evaluate to True for the assert to pass.

Visit the appendix on windows for getting started.

Using your intuition try to complete the about_asserts koans.

Making Assertions:

C:\Users\greg-lo> python3 contemplate_koans.py about_asserts

The Koans


When confused by code, break it up and use the interactive interpreter to experiment. Formulate assumptions and test them.


C:\Users\greg-lo> python3 contemplate_koans.py about_integers


C:\Users\greg-lo> python3 contemplate_koans.py about_strings
C:\Users\greg-lo> python3 contemplate_koans.py about_string_manipulation


C:\Users\greg-lo> python3 contemplate_koans.py about_if_statements


C:\Users\greg-lo> python3 contemplate_koans.py about_functions

Data Structures:

C:\Users\greg-lo> python3 contemplate_koans.py about_lists
C:\Users\greg-lo> python3 contemplate_koans.py about_dictionaries


C:\Users\greg-lo> python3 contemplate_koans.py about_loops



We need to:

  1. Download the koans zip file.
  2. Unzip it
  3. Move the unzipped folder from Downloads to your home directory (for me its C:Usersgreg-lo)

Now open cmd.exe:


Change directory (cd) into the python-koans-master directory:

C:\Users\greg-lo> cd python-koans-master

Note the updated location in the prompt.

You are setup!


You run the koans by calling the python3 interpreter on the contemplate_koans.py file followed by a name such as about_asserts:

Now we are ready to execute the contemplate_koans.py program:

C:\Users\greg-lo> python contemplate_koans.py about_asserts

The above instruction is understood as calling the python program and passing in two parameters: a file name ‘contenplate_koans.py’ and some text ‘about_asserts’.

The output should be similar to this:

Thinking AboutAsserts
  test_assert_truth has damaged your karma.

You have not yet reached enlightenment ...
  AssertionError: 0 is not true

Please meditate on the following code:
  File "/Users/greg/TEACHING/python_koans/koans/about_asserts.py", line 13, in test_assert_truth
    assert False  # replace with True

You have completed 0 koans and 0 lessons.
You are now 77 koans and 9 lessons away from reaching enlightenment.

Note the section that asks you to mediate on a file with a line number.


Open this file in SublimeText. Find SublimeText in the Start search prompt.

Open the file as specified by the output of contemplate_koans. In the above case:

  • open C:Usersgreg-lopython-koans-masterkoansabout_asserts.py
  • Go to line 13 and replace False with True.
  • Save the file.
  • Rerun the Koans

You should find that one line has gone Green and you now have a new challenge.


Arrange the windows on your screen so that you have your text editor on one side and two `cmd.exe`s on the right one above the other.

Have the command prompt open in one for running the koans.

Have the python interpreter in the other for experimenting with code.