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#!/usr/bin/env python
# Copyright (c) 2005 Gavin E. Crooks <gec@threeplusone.com>
#
# This software is distributed under the MIT Open Source License.
# <http://www.opensource.org/licenses/mit-license.html>
#
# Permission is hereby granted, free of charge, to any person obtaining a
# copy of this software and associated documentation files (the "Software"),
# to deal in the Software without restriction, including without limitation
# the rights to use, copy, modify, merge, publish, distribute, sublicense,
# and/or sell copies of the Software, and to permit persons to whom the
# Software is furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included
# in all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#
"""Read and write sequence information in FASTA format.
This is a very common format for unannotated biological sequence data,
accepted by many multiple sequence alignment programs. Each sequence
consists of a single-line description, followed by lines of sequence data.
The first character of the description line is a greater-than (">") symbol
in the first column. The first word of the description is often the name or
ID of the sequence. Fasta files containing multiple sequences have one
sequence listed right after another.
Example Fasta File ::
>Lamprey GLOBIN V - SEA LAMPREY
PIVDTGSVA-P------------------LSAAEKTKIRSAWAPVYSTY---ETSGVDILVKFFTSTPAAQEFFPKFKGL
TT-----ADQLKKSA---DVRWHA-ERIINAVNDAVASMDDTEKMS--MKL-RDLSGKH----AKSFQV-----DPQYFK
VLAAVI-AD-TVAAGD--AGFEKLMSM------I---CILLR----S-----A-----Y------------
>Hagfish GLOBIN III - ATLANTIC HAGFISH
PITDHGQPP-T------------------LSEGDKKAIRESWPQIYKNF---EQNSLAVLLEFLKKFPKAQDSFPKFSAK
KS-------HLEQDP---AVKLQA-EVIINAVNHTIGLMDKEAAMK--KYL-KDLSTKH----STEFQV-----NPDMFK
ELSAVF-VS-TMG-GK--AAYEKLFSI------I---ATLLR----S-----T-----YDA----------
>Frog HEMOGLOBIN BETA CHAIN - EDIBLE FROG
----------GS-----------------------DLVSGFWGKV--DA---HKIGGEALARLLVVYPWTQRYFTTFGNL
GSADAIC-----HNA---KVLAHG-EKVLAAIGEGLKHPENLKAHY--AKL-SEYHSNK----LHVDPANFRLLGNVFIT
VLARHF-QH-EFTPELQ-HALEAHFCA------V---GDALA----K-----A-----YH-----------
"""
from typing import Iterator, List, Optional, TextIO
from ..seq import Alphabet, Seq, SeqList
names = ("fasta", "pearson", "fa")
extensions = (
"fa",
"fasta",
"fast",
"seq",
"fsa",
"fst",
"nt",
"aa",
"fna",
"mpfa",
"faa",
"fnn",
"mfasta",
"tfa",
"pfa",
)
example = """
>Lamprey GLOBIN V - SEA LAMPREY
PIVDTGSVA-P------------------LSAAEKTKIRSAWAPVYSTY---ETSGVDILVKFFTSTPAAQEFFPKFKGL
TT-----ADQLKKSA---DVRWHA-ERIINAVNDAVASMDDTEKMS--MKL-RDLSGKH----AKSFQV-----DPQYFK
VLAAVI-AD-TVAAGD--AGFEKLMSM------I---CILLR----S-----A-----Y------------
>Hagfish GLOBIN III - ATLANTIC HAGFISH
PITDHGQPP-T------------------LSEGDKKAIRESWPQIYKNF---EQNSLAVLLEFLKKFPKAQDSFPKFSAK
KS-------HLEQDP---AVKLQA-EVIINAVNHTIGLMDKEAAMK--KYL-KDLSTKH----STEFQV-----NPDMFK
ELSAVF-VS-TMG-GK--AAYEKLFSI------I---ATLLR----S-----T-----YDA----------
>Frog HEMOGLOBIN BETA CHAIN - EDIBLE FROG
----------GS-----------------------DLVSGFWGKV--DA---HKIGGEALARLLVVYPWTQRYFTTFGNL
GSADAIC-----HNA---KVLAHG-EKVLAAIGEGLKHPENLKAHY--AKL-SEYHSNK----LHVDPANFRLLGNVFIT
VLARHF-QH-EFTPELQ-HALEAHFCA------V---GDALA----K-----A-----YH-----------
"""
def read(fin: TextIO, alphabet: Optional[Alphabet] = None) -> SeqList:
"""Read and parse a fasta file.
Args:
fin -- A stream or file to read
alphabet -- The expected alphabet of the data, if given
Returns:
SeqList -- A list of sequences
Raises:
ValueError -- If the file is unparsable
"""
seqs = [s for s in iterseq(fin, alphabet)]
name = names[0]
if hasattr(fin, "name"):
name = fin.name
return SeqList(seqs, name=name)
# def readseq(fin: TextIO, alphabet: Alphabet = None) -> Seq:
# """Read one sequence from the file, starting
# from the current file position."""
# return next(iterseq(fin, alphabet))
def iterseq(fin: TextIO, alphabet: Optional[Alphabet] = None) -> Iterator[Seq]:
"""Parse a fasta file and generate sequences.
Args:
fin -- A stream or file to read
alphabet -- The expected alphabet of the data, if given
Yields:
Seq -- One alphabetic sequence at a time.
Raises:
ValueError -- If the file is unparsable
"""
alphabet = Alphabet(alphabet)
seqs = []
comments: List[str] = [] # FIXME: comments before first sequence are lost.
header = None
header_lineno = -1
def build_seq(
seqs: List[str],
alphabet: Alphabet,
header: str,
header_lineno: int,
comments: List[str],
) -> Seq:
try:
name = header.split(" ", 1)[0]
if comments:
header += "\n" + "\n".join(comments)
s = Seq("".join(seqs), alphabet, name=name, description=header)
except ValueError:
raise ValueError(
"Parse failed with sequence starting at line %d: "
"Character not in alphabet: %s" % (header_lineno, alphabet)
)
return s
for lineno, line in enumerate(fin):
line = line.strip()
if line == "":
continue
if line.startswith(">"):
if header is not None:
yield build_seq(seqs, alphabet, header, header_lineno, comments)
header = None
seqs = []
header = line[1:]
header_lineno = lineno
comments = []
elif line.startswith(";"):
# Optional (and unusual) comment line
comments.append(line[1:])
else:
if header is None:
raise ValueError(
"Parse failed on line %d: sequence before header" % (lineno)
)
seqs.append(line)
if not seqs:
return
assert header is not None
yield build_seq(seqs, alphabet, header, header_lineno, comments)
def write(fout: TextIO, seqs: SeqList) -> None:
"""Write a fasta file.
Args:
fout -- A writable stream.
seqs -- A list of Seq's
"""
if seqs.description:
for line in seqs.description.splitlines():
print(";" + line, file=fout)
for s in seqs:
writeseq(fout, s)
def writeseq(afile: TextIO, seq: Seq) -> None:
"""Write a single sequence in fasta format.
Args:
afile -- A writable stream.
seq -- A Seq instance
"""
header = seq.description or seq.name or ""
# We prepend '>' to the first header line
# Additional lines start with ';' to indicate comment lines
if header:
headings = header.splitlines()
print(">" + headings[0], file=afile)
if len(headings) > 1:
for h in headings[1:]:
print(";" + h, file=afile)
else:
print(">", file=afile)
L = len(seq)
line_length = 80
for n in range(1 + L // line_length):
print(seq[n * line_length : (n + 1) * line_length], file=afile)
print(file=afile)
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