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to Reverse String in the Python Track

Published at Jul 13 2018 · 0 comments
Test suite

Reverse a string

For example: input: "cool" output: "looc"

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 pytest reverse_string_test.py

Alternatively, you can tell Python to run the pytest module: python -m pytest reverse_string_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/reverse-string 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.


Introductory challenge to reverse an input string https://medium.freecodecamp.org/how-to-reverse-a-string-in-javascript-in-3-different-ways-75e4763c68cb

Submitting Incomplete Solutions

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


import unittest

from reverse_string import reverse

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

class ReverseStringTest(unittest.TestCase):
    def test_an_empty_string(self):
        self.assertEqual(reverse(""), "")

    def test_a_word(self):
        self.assertEqual(reverse("robot"), "tobor")

    def test_a_capitalized_word(self):
        self.assertEqual(reverse("Ramen"), "nemaR")

    def test_a_sentence_with_punctuation(self):
        self.assertEqual(reverse("I'm hungry!"), "!yrgnuh m'I")

    def test_a_palindrome(self):
        self.assertEqual(reverse("racecar"), "racecar")

    def test_an_even_sized_word(self):
        self.assertEqual(reverse("drawer"), "reward")

if __name__ == "__main__":
def reverse(input=''):
    reversed_str = list()
    chars = list(input)
    while len(chars) > 0:
        ch = chars.pop(-1)
    return ''.join(reversed_str)

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