--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/long_reads_sampling.py	Fri Dec 08 09:57:17 2017 -0500
@@ -0,0 +1,98 @@
+#!/usr/bin/env python3
+import sys
+import argparse
+import random
+from argparse import ArgumentDefaultsHelpFormatter
+from Bio import SeqIO
+from long2short import get_sequences_summary
+
+
+def get_args():
+    '''Parses command line arguments '''
+    description = ("Create sample of long reads, instead"
+                   " of setting number of reads to be sampled,"
+                   "total length of all sampled sequences is defined")
+
+    parser = argparse.ArgumentParser(
+        description=description,
+        formatter_class=ArgumentDefaultsHelpFormatter)
+    parser.add_argument('-i',
+                        '--input',
+                        type=argparse.FileType('r'),
+                        help="file with long reads in fasta format")
+    parser.add_argument('-o',
+                        '--output',
+                        type=argparse.FileType('w'),
+                        help="Output file name")
+    parser.add_argument("-l",
+                        "--total_length",
+                        type=int,
+                        help="total length of sampled output")
+
+    parser.add_argument("-s",
+                        "--seed",
+                        type=int,
+                        default=123,
+                        help="random number generator seed")
+
+    args = parser.parse_args()
+    if len(sys.argv) == 1:
+        parser.print_help()
+        sys.exit(1)
+
+    return args
+
+
+def make_sequence_sample(args, seq_summary):
+    '''
+    create output sequence of required length or larger, save to fasta
+    '''
+    random.seed(args.seed)
+    print(args.seed)
+    selected_seq_id = set()
+    cummulative_length = 0
+    for seq_id in random.sample(seq_summary.id_length.keys(),
+                                seq_summary.number_of_sequence):
+        selected_seq_id.add(seq_id)
+        cummulative_length += seq_summary.id_length[seq_id]
+        if cummulative_length >= args.total_length:
+            break
+    print(selected_seq_id)
+    # to make it efficient same orger is necesary
+    selected_seq_id_ordered = [i
+                               for i in seq_summary.id_length
+                               if i in selected_seq_id]
+    curent_id = selected_seq_id_ordered.pop(0)
+    with open(args.output.name, 'w') as output_seq_file:
+        for seqs in SeqIO.parse(args.input.name, "fasta"):
+            if seqs.id == curent_id:
+                SeqIO.write(seqs, output_seq_file, "fasta")
+                try:
+                    curent_id = selected_seq_id_ordered.pop(0)
+                except IndexError:
+                    break
+
+
+def main():
+    '''
+    Create sample of longn reads, sample size is defined as total length
+    '''
+    args = get_args()
+    seq_summary = get_sequences_summary(args.input)
+    # check that total length if larger than required sampling
+    if seq_summary.total_length < args.total_length:
+        print("Input sequences total length: ",
+              seq_summary.total_length,
+              file=sys.stderr)
+        print("Required output total length: ",
+              args.total_length,
+              file=sys.stderr)
+        print("Required sequence length is larger than input data, exiting",
+              file=sys.stderr)
+        sys.exit(1)
+
+    make_sequence_sample(args, seq_summary)
+
+
+if __name__ == "__main__":
+    main()