Pov in Python
Reparent a graph on a selected node
exercism fetch python pov
Reparent a graph on a selected node.
This exercise is all about re-orientating a graph to see things from a different point of view. For example family trees are usually presented from the ancestor's perspective:
But the same information can be presented from the perspective of any other node in the graph, by pulling it up to the root and dragging its relationships along with it. So the same graph from 6's perspective would look like:
This lets us more simply describe the paths between two nodes. So for example the path from 6-9 (which in the first graph goes up to the root and then down to a different leaf node) can be seen to follow the path 6-2-0-3-9
This exercise involves taking an input graph and re-orientating it from the point of view of one of the nodes.
Sometimes it is necessary to raise an exception. When you do this, you should include a meaningful error message to indicate what the source of the error is. This makes your code more readable and helps significantly with debugging. Not every exercise will require you to raise an exception, but for those that do, the tests will only pass if you include a message.
To raise a message with an exception, just write it as an argument to the exception type. For example, instead of
raise Exception, you should write:
raise Exception("Meaningful message indicating the source of the error")
Running the tests
To run the tests, run the appropriate command below (why they are different):
- Python 2.7:
- Python 3.3+:
Alternatively, you can tell Python to run the pytest module (allowing the same command to be used regardless of Python version):
python -m pytest pov_test.py
-v: enable verbose output
-x: stop running tests on first failure
--ff: run failures from previous test before running other test cases
For other options, see
python -m pytest -h
Note that, when trying to submit an exercise, make sure the solution is in the
You can find your Exercism workspace by running
exercism debug and looking for the line that starts with
For more detailed information about running tests, code style and linting, please see the help page.
Adaptation of exercise from 4clojure https://www.4clojure.com/
Submitting Incomplete Solutions
It's possible to submit an incomplete solution so you can see how others have completed the exercise.