STAGE 3 OF 5

Filter by length

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THE BRIEF

Very short sequences rarely carry enough information to be useful, and many analyses set a minimum length.

Your task. The first line of the input is a whole number, the minimum length. The rest of the input is a FASTA file. Clean each sequence as in the previous stage (uppercase, whitespace removed), then print the ids of the records whose sequence length is at least the minimum, one per line, in their original order. If no record qualifies, print NONE.

Input. A minimum length, then a FASTA file.

Output. The qualifying ids, one per line, or NONE.

GIVEN INPUT

Your code reads this from standard input (input() or sys.stdin), both here and when it is graded.

8
>short
ACGT
>exact
ACGTACGT
>long
ACGTACGTACGTACGT
>spaced
ACG TAC GT

EXPECTED OUTPUT FOR THIS INPUT

exact
long
spaced

SKILLS YOU'LL USE

Stuck? These bank problems practise the same techniques.

Filter Sequences by Length

Write your code

.ipynb

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Why do pipelines usually discard very short sequences?

Short sequences are always incorrect They carry little information and can align to many places by chance, which adds noise to later steps Short sequences cannot be stored in a file The sequencer cannot read short DNA

A record's sequence is exactly the minimum length. With the rule "at least", is it kept?

Yes, because the length is greater than or equal to the minimum No, only longer sequences are kept It depends on the id It is kept only if it contains an N

Explain and submit

Explain how you compute each record's length and how you handled the case where no record qualifies.

Submitting sends the code in your solution cell and this explanation. The code is checked on our server against the given input and hidden tests. The stage is complete when the code passes and the explanation has at least 20 words.

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