New line when using % formatting in python

Question

I'm trying to print a new line while using % formatting. This is the code I have:

return '%s\n%s\n%s\nScore: %d' % (seqA, matches, seqB, score)

But that prints:

'ATTCGT\n||   |\nATCTAT\nScore: 2'

Is there a way to print new lines using this method?

You're confusing the diagnostics the Python shell prints (a representation, using the repr function, of the result of the previous line evaluated) with actual output of your script. Your code doesn't actually output anything. — Cairnarvon
– Cairnarvon, Commented May 10, 2013 at 2:34
I just tried it outside the Python IDLE program, and used 'print' and it worked. Sorry. — Philip Kenny
– Philip Kenny, Commented May 10, 2013 at 2:35
The question is part of a pyschools challenge. 'Pairwise comparision of DNA sequences is a popular technique used in Bioinformatics. It usually involves some scoring scheme to express the degree of similarity. Write a function that compares two DNA sequences based on the following scoring scheme: +1 for a match, +3 for each consecutive match and -1 for each mismatch.' That's why I was using 'return'. I was struggling to get it right in their code editor so I tried IDLE. That was giving me the output in the OP, so I thought I was missing something. — Philip Kenny
– Philip Kenny, Commented May 10, 2013 at 2:43

Justin O Barber · Accepted Answer · 2013-05-10 02:40:31Z

1

Use print instead of return. print evaluates each expression and writes the result to standard output, whereas return merely echoes the returned object (in IDLE):

>>> seqA = 'ATTCGT'
>>> matches = '||   |'
>>> seqB = 'ATCTAT'
>>> score = 2
>>> print '%s\n%s\n%s\nScore: %d' % (seqA, matches, seqB, score)
ATTCGT
||   |
ATCTAT
Score: 2

edited May 10, 2013 at 2:40

answered May 10, 2013 at 2:25

Justin O Barber

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2 Comments

Cairnarvon Over a year ago

I feel like this answer is just inaccurate enough to be unhelpful, though it technically probably will solve his problem.

Justin O Barber Over a year ago

I've adjusted the answer to reflect more appropriate terminology. Thanks for the prompt.

Ade YU · Accepted Answer · 2013-05-10 02:32:28Z

0

You get the value correctly. But you need the print it.

answered May 10, 2013 at 2:32

Ade YU

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