def load_index_from_text(self, index_filename=''):
"""
Load an index from a _text file on disk.
"""
start_time = datetime.datetime.now()
verbose_print('Loading index from {} ...'.format(index_filename))
# It's faster to create an interval tree from a list of tuples than from adding intervals one at a time
index_tuples = {}
with gzip.open(index_filename, 'rt') as index_file:
line = index_file.readline()
split_line = line.rstrip().split('\t')
self.line_length_file_distance = int(split_line[0])
self.line_length_text_distance = int(split_line[1])
line = index_file.readline()
contig = None
while line is not '':
if line.startswith('>'):
contig = line.rstrip()[1:]
index_tuples[contig] = []
else:
index_tuples[contig].append(
[int(val) for val in line.rstrip().split('\t')])
line = index_file.readline()
self._index = {}
for contig in index_tuples:
self._index[contig] = intervaltree.IntervalTree.from_tuples(
index_tuples[contig])
verbose_print('\tDone in {}.'.format(datetime.datetime.now() -
start_time))
def _assign_blocks_to_contigs(contig_intervals_file_distance,
block_interval_tree):
"""
For each contig, create an interval tree that stores the sequence interval stored in each block
(for all blocks that contain part of the contig), as well as the offset of the start of that block.
:param contig_intervals_file_distance: A dictionary of intervals, keyed by contig name,
storing the locations in the file spanned by each contig.
:param block_interval_tree: An interval tree storing the start and end locations in the uncompressed
file spanned by each compressed block, as well as the offset of the block start.
:return: Return a dictionary of such interval trees keyed by contig name.
"""
start_time = datetime.datetime.now()
verbose_print('\tAssigning compressed blocks to sequence contigs ...')
sequence_blocks = {}
for contig in sorted(contig_intervals_file_distance):
if contig not in sequence_blocks:
sequence_blocks[contig] = intervaltree.IntervalTree()
for block_interval in block_interval_tree.search(
*contig_intervals_file_distance[contig]):
block_start_text_distance = block_interval.begin - contig_intervals_file_distance[
contig][0]
block_end_text_distance = block_interval.end - contig_intervals_file_distance[
contig][0]
sequence_blocks[contig].addi(block_start_text_distance,
block_end_text_distance,
block_interval.data)
verbose_print('\t\tDone in {}.'.format(datetime.datetime.now() -
start_time))
return sequence_blocks
def populate_blocks():
with open(self.bgzipped_fasta_filename,
'rb') as fasta_file_for_blocks:
# Store uncompressed data start, uncompressed data end, compressed block start as a tuple
blocks = [(b[2], b[2] + b[3], b[0])
for b in bgzf.BgzfBlocks(fasta_file_for_blocks)]
verbose_print('\t\tFound {} blocks in {}'.format(
len(blocks),
datetime.datetime.now() - start_time))
return blocks
def save_contig_lengths(self, contig_length_filename):
"""
Saves the length of each contig to a tab-delimited 2-column table in :param:`contig_length_filename`
"""
verbose_print('Saving {} contig lengths to {} ...'.format(
len(self._contig_lengths), contig_length_filename))
with open(contig_length_filename, 'wt') as contig_length_file:
for contig_name, contig_length in sorted(
self._contig_lengths.items()):
contig_length_file.write('{}\t{}\n'.format(
contig_name, contig_length))
verbose_print('\tDone.')
def _compute_contig_lengths(self, contig_intervals_file_distance):
verbose_print('\tComputing contig lengths ...')
self._contig_lengths = {}
for contig in sorted(contig_intervals_file_distance):
self._contig_lengths[contig] = self._file_distance_to_text_distance(
offset_file_distance=contig_intervals_file_distance[contig][1],
sequence_start_file_distance=contig_intervals_file_distance[contig][0]) - \
self._file_distance_to_text_distance(
offset_file_distance=contig_intervals_file_distance[contig][0],
sequence_start_file_distance=contig_intervals_file_distance[contig][
0]) - 1
verbose_print('\t\tDone.')
def save_index_to_text(self, index_filename=''):
"""
Save the current index to a _text file on disk.
"""
start_time = datetime.datetime.now()
verbose_print('Saving index to {} ...'.format(index_filename))
with gzip.open(index_filename, 'wt') as index_file:
index_file.write('{}\t{}\n'.format(self.line_length_file_distance,
self.line_length_text_distance))
for contig, intervals in sorted(self._index.items()):
index_file.write('>{}\n'.format(contig))
for interval in intervals:
index_file.write('{}\t{}\t{}\n'.format(
interval.begin, interval.end, interval.data))
verbose_print('\tDone in {}.'.format(datetime.datetime.now() -
start_time))
def load_contig_lengths(self, contig_length_filename):
"""
Retrieve the length of each contig from a tab-delimited 2-column table in :param:`contig_length_filename`
:param contig_length_filename:
:return:
"""
verbose_print('Loading contig lengths from {} ...'.format(
contig_length_filename))
self._contig_lengths = {}
with open(contig_length_filename, 'rt') as contig_length_file:
for line in contig_length_file:
split_line = line.split('\t')
contig_name = split_line[0]
contig_length = int(split_line[1])
self._contig_lengths[contig_name] = contig_length
verbose_print('Loaded {} contig lengths.'.format(
len(self._contig_lengths)))
def _get_contig_intervals_file_distance(self):
"""
Determine the start and end locations of each contig sequence (not including headers) in the file.
"""
start_time = datetime.datetime.now()
contig_intervals_file_distance = {}
verbose_print('\tFinding contig locations ...')
previous_sequence = None
previous_start = 0
line = None
with gzip.open(self.bgzipped_fasta_filename, 'rb') as fasta_file:
for line_num, line in enumerate(fasta_file):
if line_num % 10000000 == 0:
verbose_print(
'\t\tprocessing line {:>10} ...'.format(line_num + 1))
if line.startswith(b'>'):
sequence_name = re.split(WHITESPACE, line[1:].decode())[0]
if previous_sequence:
contig_intervals_file_distance[previous_sequence] = (
previous_start, fasta_file.tell() - len(line))
previous_start = fasta_file.tell()
previous_sequence = sequence_name
contig_intervals_file_distance[previous_sequence] = (
previous_start, fasta_file.tell() - len(line))
verbose_print('\t\tFound {} sequences in {}.'.format(
len(contig_intervals_file_distance),
datetime.datetime.now() - start_time))
return contig_intervals_file_distance
def _get_blocks(self):
"""
Return a tuple for each compressed block in the bzgipped FASTA file, consisting of
(binary_start, file_end, file_block_start)
"""
start_time = datetime.datetime.now()
verbose_print('\tFinding block boundaries ...')
def populate_blocks():
with open(self.bgzipped_fasta_filename,
'rb') as fasta_file_for_blocks:
# Store uncompressed data start, uncompressed data end, compressed block start as a tuple
blocks = [(b[2], b[2] + b[3], b[0])
for b in bgzf.BgzfBlocks(fasta_file_for_blocks)]
verbose_print('\t\tFound {} blocks in {}'.format(
len(blocks),
datetime.datetime.now() - start_time))
return blocks
try:
blocks = populate_blocks()
except ValueError:
verbose_print(
'This does not appear to be a valid block-gzipped file. Converting to bgzipped format ...'
)
convert_start_time = datetime.datetime.now()
convert_gzipped_to_bgzipped(self.bgzipped_fasta_filename)
verbose_print('\tDone in {}.'.format(datetime.datetime.now() -
convert_start_time))
blocks = populate_blocks()
return blocks[:-1] # Omit the last, empty block
def get_sequence(self, contig, start, end, strand=1, all_upper=False):
"""
Return the genomic DNA sequence spanning [start, end) on contig.
:param contig: The name of the contig on which the start and end coordinates are located
:param start: The start location of the sequence to be returned (this endpoint is included in the interval)
:param end: The end location of the sequence to be returned (tis endpoint is not included in the interval)
:param strand: The DNA strand of the sequence to be returned (-1 for negative strand, 1 for positive strand)
:param all_upper: If true, return the sequence in all uppercase letters. Otherwise return lowercase letters
for positions that are "soft-masked" (see https://genomevolution.org/wiki/index.php/Masked).
:return: A string of DNA nucleotides of length end-start
"""
if contig not in self._index:
raise ContigNotFound(message='Contig {} not found'.format(contig),
requested_contig=contig,
valid_contigs=list(self._index.keys()))
if start < 0:
raise CoordinateOutOfBounds(
message='Start coordinate below 0',
problematic_coordinate=start,
problem_with_start=True,
coordinate_too_small=True,
valid_coordinate_range=(0, self.contig_lengths[contig]),
current_contig=contig)
if start > self.contig_lengths[contig]:
raise CoordinateOutOfBounds(
message='Start coordinate past end of contig',
problematic_coordinate=start,
problem_with_start=True,
coordinate_too_small=False,
valid_coordinate_range=(0, self.contig_lengths[contig]),
current_contig=contig)
if end > self.contig_lengths[contig]:
raise CoordinateOutOfBounds(
message='End coordinate past end of contig',
problematic_coordinate=end,
problem_with_start=False,
coordinate_too_small=False,
valid_coordinate_range=(0, self.contig_lengths[contig]),
current_contig=contig)
if end < 0:
raise CoordinateOutOfBounds(
message='End coordinate below 0',
problematic_coordinate=end,
problem_with_start=False,
coordinate_too_small=True,
valid_coordinate_range=(0, self.contig_lengths[contig]),
current_contig=contig)
if start >= end:
raise InvalidCoordinates(start=start, end=end)
query_length = end - start
start_pos_file_distance = self._text_distance_to_file_distance(start)
start_block = sorted(
self._index[contig].search(start_pos_file_distance))[0]
start_block_offset = start_block.data
verbose_print('Retrieving sequence for {} [{},{}) ...'.format(
contig, start, end))
sequence_start_offset = start_pos_file_distance - start_block.begin
retrieved_sequence = ''
with bgzf.BgzfReader(self.bgzipped_fasta_filename, 'rt') as fasta_file:
fasta_file.seek(
bgzf.make_virtual_offset(start_block_offset,
sequence_start_offset))
while len(retrieved_sequence) < query_length:
retrieved_sequence += fasta_file.readline().rstrip()
trimmed_sequence = retrieved_sequence[:query_length]
if all_upper:
trimmed_sequence = trimmed_sequence.upper()
if strand == -1:
return reverse_complement(trimmed_sequence)
else:
return trimmed_sequence
def generate_index(self):
"""
Generate an index for the FASTA file and store it in memory.
"""
overall_start_time = datetime.datetime.now()
verbose_print('Generating index for sequence file {} ...'.format(
self.bgzipped_fasta_filename))
block_intervals_file_distance = self._get_blocks()
start_time = datetime.datetime.now()
verbose_print('\tGenerating interval tree from block spans ...')
block_interval_tree = intervaltree.IntervalTree.from_tuples(
block_intervals_file_distance)
del block_intervals_file_distance
verbose_print('\t\tDone in {}.'.format(datetime.datetime.now() -
start_time))
self.line_length_file_distance = self._compute_file_line_length()
verbose_print('\tEstimated file line size as {}.'.format(
self.line_length_file_distance))
self.line_length_text_distance = self._compute_text_line_length()
verbose_print('\tEstimated _text line size as {}.'.format(
self.line_length_text_distance))
contig_intervals_file_distance = self._get_contig_intervals_file_distance(
)
self._index = self._assign_blocks_to_contigs(
contig_intervals_file_distance=contig_intervals_file_distance,
block_interval_tree=block_interval_tree)
self._compute_contig_lengths(
contig_intervals_file_distance=contig_intervals_file_distance)
verbose_print('\tDone in {}.'.format(datetime.datetime.now() -
overall_start_time))
