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rootulp's solution

to Series in the Python Track

Published at Jul 13 2018 · 0 comments
Test suite


This solution was written on an old version of Exercism. The tests below might not correspond to the solution code, and the exercise may have changed since this code was written.

Given a string of digits, output all the contiguous substrings of length n in that string in the order that they appear.

For example, the string "49142" has the following 3-digit series:

  • "491"
  • "914"
  • "142"

And the following 4-digit series:

  • "4914"
  • "9142"

And if you ask for a 6-digit series from a 5-digit string, you deserve whatever you get.

Note that these series are only required to occupy adjacent positions in the input; the digits need not be numerically consecutive.

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 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: py.test series_test.py
  • Python 3.4+: pytest series_test.py

Alternatively, you can tell Python to run the pytest module (allowing the same command to be used regardless of Python version): python -m pytest series_test.py

Common pytest options

  • -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

Submitting Exercises

Note that, when trying to submit an exercise, make sure the solution is in the $EXERCISM_WORKSPACE/python/series directory.

You can find your Exercism workspace by running exercism debug and looking for the line that starts with Workspace.

For more detailed information about running tests, code style and linting, please see Running the Tests.


A subset of the Problem 8 at Project Euler http://projecteuler.net/problem=8

Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.


"""Tests for the series exercise

Implementation note:
The slices function should raise a ValueError with a meaningful error
message if its length argument doesn't fit the series.
import unittest

from series import slices

# Tests adapted from `problem-specifications//canonical-data.json` @ v1.0.0

class SeriesTest(unittest.TestCase):
    def test_slices_of_one_from_one(self):
        self.assertEqual(slices("1", 1), ["1"])

    def test_slices_of_one_from_two(self):
        self.assertEqual(slices("12", 1), ["1", "2"])

    def test_slices_of_two(self):
        self.assertEqual(slices("35", 2), ["35"])

    def test_slices_of_two_overlap(self):
        self.assertEqual(slices("9142", 2), ["91", "14", "42"])

    def test_slices_can_include_duplicates(self):
        self.assertEqual(slices("777777", 3), ["777", "777", "777", "777"])

    def test_slice_length_is_too_large(self):
        with self.assertRaisesWithMessage(ValueError):
            slices("12345", 6)

    def test_slice_length_cannot_be_zero(self):
        with self.assertRaisesWithMessage(ValueError):
            slices("12345", 0)

    def test_slice_length_cannot_be_negative(self):
        with self.assertRaisesWithMessage(ValueError):
            slices("123", -1)

    def test_empty_series_is_invalid(self):
        with self.assertRaisesWithMessage(ValueError):
            slices("", 1)

    # Utility functions
    def setUp(self):
        except AttributeError:
            self.assertRaisesRegex = self.assertRaisesRegexp

    def assertRaisesWithMessage(self, exception):
        return self.assertRaisesRegex(exception, r".+")

if __name__ == '__main__':
def slices(string, length):
    if length <= 0 or length > len(string):
        raise ValueError('Invalid slice length')

    return [string[i:i+length] for i in range(len(string) - length + 1)]

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