create utils.round_sig() for rounding number to n sig figures

Author: tdudgeon

src/python/pipelines_utils/utils.py

@@ -17,6 +17,7 @@
 
 from __future__ import print_function
 import sys, gzip, json, uuid
+from math import log10, floor
 from rdkit import Chem
 from rdkit.Chem import AllChem
 from rdkit_utils.sanifix import fix_mol
@@ -31,6 +32,10 @@ def log(*args, **kwargs):
     """
     print(*args, file=sys.stderr, **kwargs)
 
+def round_sig(x, sig):
+    """Round the number to the specified number of significant figures"""
+    return round(x, sig-int(floor(log10(abs(x))))-1)
+
 def add_default_input_args(parser):
     parser.add_argument('-i', '--input', help="Input file, if not defined the STDIN is used")
     parser.add_argument('-if', '--informat', choices=['sdf', 'json'], help="Input format. When using STDIN this must be specified.")

src/python/test/pipelines_utils/test_utils.py

@@ -0,0 +1,15 @@
+import unittest
+
+from pipelines_utils import utils
+
+
+class UtilsTestCase(unittest.TestCase):
+
+
+    def test_round_sig(self):
+        """Rounding of significant figures
+        """
+        self.assertEquals(utils.round_sig(1.23456789, 2), 1.2)
+        self.assertEquals(utils.round_sig(1.23456789, 3), 1.23)
+        self.assertEquals(utils.round_sig(1.23456789, 6), 1.23457)
+