Given a string representing a matrix of numbers, return the rows and columns of that matrix.
So given a string with embedded newlines like:
9 8 7 5 3 2 6 6 7
representing this matrix:
1 2 3 |--------- 1 | 9 8 7 2 | 5 3 2 3 | 6 6 7
your code should be able to spit out:
The rows for our example matrix:
And its columns:
In this exercise you're going to create a class. Don't worry, it's not as complicated as you think!
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")
To run the tests, run
Alternatively, you can tell Python to run the pytest module:
python -m pytest matrix_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 Running the Tests.
Warmup to the
saddle-points warmup. http://jumpstartlab.com
It's possible to submit an incomplete solution so you can see how others have completed the exercise.
import unittest from matrix import Matrix # Tests adapted from `problem-specifications//canonical-data.json` class MatrixTest(unittest.TestCase): def test_extract_row_from_one_number_matrix(self): matrix = Matrix("1") self.assertEqual(matrix.row(1), ) def test_can_extract_row(self): matrix = Matrix("1 2\n3 4") self.assertEqual(matrix.row(2), [3, 4]) def test_extract_row_where_numbers_have_different_widths(self): matrix = Matrix("1 2\n10 20") self.assertEqual(matrix.row(2), [10, 20]) def test_can_extract_row_from_non_square_matrix_with_no_corresponding_column(self): matrix = Matrix("1 2 3\n4 5 6\n7 8 9\n8 7 6") self.assertEqual(matrix.row(4), [8, 7, 6]) def test_extract_column_from_one_number_matrix(self): matrix = Matrix("1") self.assertEqual(matrix.column(1), ) def test_can_extract_column(self): matrix = Matrix("1 2 3\n4 5 6\n7 8 9") self.assertEqual(matrix.column(3), [3, 6, 9]) def test_can_extract_column_from_non_square_matrix_with_no_corresponding_row(self): matrix = Matrix("1 2 3 4\n5 6 7 8\n9 8 7 6") self.assertEqual(matrix.column(4), [4, 8, 6]) def test_extract_column_where_numbers_have_different_widths(self): matrix = Matrix("89 1903 3\n18 3 1\n9 4 800") self.assertEqual(matrix.column(2), [1903, 3, 4]) if __name__ == "__main__": unittest.main()
class Matrix(object): def __init__(self, matrix_string): self.matrix = [[int(element) for element in row.split(' ') ] for row in matrix_string.split('\n')] def row(self, index): return self.matrix[index - 1] def column(self, index): return [row[index - 1] for row in self.matrix]
A huge amount can be learned from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.
Here are some questions to help you reflect on this solution and learn the most from it.