add function to parse canonical quantities (e.g. resources)

This utility function is useful to parse values like the 200m or 300Gi
memory and cpu resources stored in kubernetes manifests.
The function only supports the "canonical form" which has no fractional
digits.

kubernetes/test/test_quantity.py

@@ -0,0 +1,71 @@
+# coding: utf-8
+# Copyright 2019 The Kubernetes Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from __future__ import absolute_import
+
+import unittest
+from kubernetes.utils import parse_quantity
+
+
+class TestQuantity(unittest.TestCase):
+    def test_parse(self):
+        self.assertEqual(parse_quantity(2), 2)
+        self.assertEqual(parse_quantity(2.), 2)
+        self.assertEqual(parse_quantity("123"), 123)
+        self.assertEqual(parse_quantity("2"), 2)
+        self.assertEqual(parse_quantity("2m"), 0.002)
+        self.assertEqual(parse_quantity("223k"), 223000)
+        self.assertEqual(parse_quantity("002M"), 2 * 1000**2)
+        self.assertEqual(parse_quantity("2M"), 2 * 1000**2)
+        self.assertEqual(parse_quantity("4123G"), 4123 * 1000**3)
+        self.assertEqual(parse_quantity("2T"), 2 * 1000**4)
+        self.assertEqual(parse_quantity("2P"), 2 * 1000**5)
+        self.assertEqual(parse_quantity("2E"), 2 * 1000**6)
+
+        self.assertEqual(parse_quantity("2m"), 0.002)
+        self.assertEqual(parse_quantity("223Ki"), 223 * 1024)
+        self.assertEqual(parse_quantity("002Mi"), 2 * 1024**2)
+        self.assertEqual(parse_quantity("2Mi"), 2 * 1024**2)
+        self.assertEqual(parse_quantity("2Gi"), 2 * 1024**3)
+        self.assertEqual(parse_quantity("4123Gi"), 4123 * 1024**3)
+        self.assertEqual(parse_quantity("2Ti"), 2 * 1024**4)
+        self.assertEqual(parse_quantity("2Pi"), 2 * 1024**5)
+        self.assertEqual(parse_quantity("2Ei"), 2 * 1024**6)
+
+    def test_parse_invalid(self):
+        self.assertRaises(ValueError, parse_quantity, "bla")
+        self.assertRaises(ValueError, parse_quantity, "Ki")
+        self.assertRaises(ValueError, parse_quantity, "M")
+        self.assertRaises(ValueError, parse_quantity, "2ki")
+        self.assertRaises(ValueError, parse_quantity, "2Ki ")
+        self.assertRaises(ValueError, parse_quantity, "20Ki ")
+        self.assertRaises(ValueError, parse_quantity, "2MiKi")
+        self.assertRaises(ValueError, parse_quantity, "2MK")
+        self.assertRaises(ValueError, parse_quantity, "2MKi")
+        self.assertRaises(ValueError, parse_quantity, "234df")
+        self.assertRaises(ValueError, parse_quantity, "df234")
+        self.assertRaises(ValueError, parse_quantity, tuple())
+        # canonical format has no fractional digits
+        self.assertRaises(ValueError, parse_quantity, "2.34Ki ")
+        self.assertRaises(ValueError, parse_quantity, "2.34B")
+        self.assertRaises(ValueError, parse_quantity, "2.34Bi")
+        self.assertRaises(ValueError, parse_quantity, "2.34")
+        self.assertRaises(ValueError, parse_quantity, ".34")
+        self.assertRaises(ValueError, parse_quantity, "34.")
+        self.assertRaises(ValueError, parse_quantity, ".34M")
+
+
+if __name__ == '__main__':
+    unittest.main()

kubernetes/utils/__init__.py

@@ -16,3 +16,4 @@
 
 from .create_from_yaml import (FailToCreateError, create_from_dict,
                                create_from_yaml)
+from .quantity import parse_quantity

kubernetes/utils/quantity.py

@@ -0,0 +1,70 @@
+# Copyright 2019 The Kubernetes Authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import re
+
+
+def parse_quantity(quantity):
+    """
+    Parse kubernetes canonical form quantity like 200Mi to an float number.
+    Supported SI suffixes:
+    base1024: Ki | Mi | Gi | Ti | Pi | Ei
+    base1000: m | "" | k | M | G | T | P | E
+
+    Input:
+    quanity: string. kubernetes canonical form quantity
+
+    Returns:
+    float
+
+    Raises:
+    ValueError on invalid or unknown input
+    """
+    exponents = {"m": -1, "K": 1, "k": 1, "M": 2,
+                 "G": 3, "T": 4, "P": 5, "E": 6}
+    pattern = r"^(\d+)([^\d]{1,2})?$"
+
+    if isinstance(quantity, (int, float)):
+        return float(quantity)
+
+    quantity = str(quantity)
+
+    res = re.match(pattern, quantity)
+    if not res:
+        raise ValueError(
+            "{} did not match pattern {}".format(quantity, pattern)
+        )
+    number, suffix = res.groups()
+    number = float(number)
+
+    if suffix is None:
+        return number
+
+    suffix = res.groups()[1]
+
+    if suffix.endswith("i"):
+        base = 1024
+    elif len(suffix) == 1:
+        base = 1000
+    else:
+        raise ValueError("{} has unknown suffix".format(quantity))
+
+    # handly SI inconsistency
+    if suffix == "ki":
+        raise ValueError("{} has unknown suffix".format(quantity))
+
+    if suffix[0] not in exponents:
+        raise ValueError("{} has unknown suffix".format(quantity))
+
+    exponent = exponents[suffix[0]]
+    return number * (base ** exponent)