Given a DNA strand, return its RNA complement (per RNA transcription).
Both DNA and RNA strands are a sequence of nucleotides.
The four nucleotides found in DNA are adenine (A), cytosine (C), guanine (G) and thymine (T).
The four nucleotides found in RNA are adenine (A), cytosine (C), guanine (G) and uracil (U).
Given a DNA strand, its transcribed RNA strand is formed by replacing each nucleotide with its complement:
Your function will need to be able to handle invalid inputs by raising a
ValueError with a meaningful message.
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 the appropriate command below (why they are different):
Alternatively, you can tell Python to run the pytest module (allowing the same command to be used regardless of Python version):
python -m pytest rna_transcription_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
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import unittest from rna_transcription import to_rna # Tests adapted from `problem-specifications//canonical-data.json` @ v1.2.0 class RnaTranscriptionTest(unittest.TestCase): def test_transcribes_cytosine_to_guanine(self): self.assertEqual(to_rna('C'), 'G') def test_transcribes_guanine_to_cytosine(self): self.assertEqual(to_rna('G'), 'C') def test_transcribes_thymine_to_adenine(self): self.assertEqual(to_rna('T'), 'A') def test_transcribes_adenine_to_uracil(self): self.assertEqual(to_rna('A'), 'U') def test_transcribes_all_occurrences(self): self.assertEqual(to_rna('ACGTGGTCTTAA'), 'UGCACCAGAAUU') if __name__ == '__main__': unittest.main()
import string def to_rna(dna): accept = 'GCTA' trans = string.maketrans('GCTA', 'CGAU') for letter in dna: if letter not in accept: return '' return dna.translate(trans)
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.