# POV Reparent a graph on a selected node. # Tree Reparenting 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: ```text +------0------+ | | | +-1-+ +-2-+ +-3-+ | | | | | | 4 5 6 7 8 9 ``` 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: ```text 6 | +-----2-----+ | | 7 +-----0-----+ | | +-1-+ +-3-+ | | | | 4 5 8 9 ``` 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. ## Exception messages 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 shold write: ```python raise Exception("Meaningful message indicating the source of the error") ``` ## Submitting Exercises Note that, when trying to submit an exercise, make sure the solution is in the `exercism/python/` directory. For example, if you're submitting `bob.py` for the Bob exercise, the submit command would be something like `exercism submit /python/bob/bob.py`. For more detailed information about running tests, code style and linting, please see the [help page](http://exercism.io/languages/python). ## Source Adaptation of exercise from 4clojure [https://www.4clojure.com/](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.