allow to test if index is present

python/README.md

@@ -23,6 +23,7 @@ The following Python program shows the key functionality of this module:
 ```python
 import minimap2 as mm
 a = mm.Aligner("test/MT-human.fa")
+if not a: raise Exception("ERROR: failed to load/build index")
 for hit in a.map("GGTTAAATACAGACCAAGAGCCTTCAAAGCCCTCAGTAAGTTGCAATACTTAATTTCTGT"):
 	print("{}\t{}\t{}\t{}".format(hit.ctg, hit.r_st, hit.r_en, hit.cigar_str))
 ```

python/minimap2.pyx

@@ -110,6 +110,9 @@ cdef class Aligner:
 		if self._idx is not NULL:
 			cminimap2.mm_idx_destroy(self._idx)
 
+	def __bool__(self):
+		return (self._idx != NULL)
+
 	def map(self, seq, buf=None):
 		cdef cminimap2.mm_reg1_t *regs
 		cdef cminimap2.mm_hitpy_t h

python/mm2-lite.py

@@ -40,6 +40,9 @@ def main(argv):
 		print("Usage: mm2-lite.py <ref.fa>|<ref.mmi> <query.fq>")
 		sys.exit(1)
 	a = mm.Aligner(args[0]) # load/build index
+	if not a:
+		print("ERROR: failed to load/build index")
+		return
 	for name, seq, qual in readfq(open(args[1])): # read one sequence
 		for h in a.map(seq): # traverse hits
 			print('{}\t{}\t{}'.format(name, len(seq), h))

setup.py

@@ -11,7 +11,7 @@ sys.path.append('python')
 
 setup(
 	name = 'minimap2',
-	version = '2.1.1',
+	version = '2.2rc',
 	url = 'https://github.com/lh3/minimap2',
 	description = 'Minimap2 python binding',
 	author = 'Heng Li',