str2list utility for commandline parsing of comma separated lists

monai/utils/__init__.py

@@ -78,6 +78,7 @@
     set_determinism,
     star_zip_with,
     str2bool,
+    str2list,
     zip_with,
 )
 from .module import (

monai/utils/misc.py

@@ -47,6 +47,7 @@
     "MAX_SEED",
     "copy_to_device",
     "str2bool",
+    "str2list",
     "MONAIEnvVars",
     "ImageMetaKey",
     "is_module_ver_at_least",
@@ -363,21 +364,29 @@ def copy_to_device(
     return obj
 
 
-def str2bool(value: str, default: bool = False, raise_exc: bool = True) -> bool:
+def str2bool(value: Union[str, bool], default: bool = False, raise_exc: bool = True) -> bool:
     """
     Convert a string to a boolean. Case insensitive.
     True: yes, true, t, y, 1. False: no, false, f, n, 0.
 
     Args:
-        value: string to be converted to a boolean.
+        value: string to be converted to a boolean. If value is a bool already, simply return it.
         raise_exc: if value not in tuples of expected true or false inputs,
-            should we raise an exception? If not, return `None`.
+            should we raise an exception? If not, return `default`.
     Raises
         ValueError: value not in tuples of expected true or false inputs and
             `raise_exc` is `True`.
+    Useful with argparse, for example:
+        parser.add_argument("--convert", default=False, type=str2bool)
+        python mycode.py --convert=True
     """
+
+    if isinstance(value, bool):
+        return value
+
     true_set = ("yes", "true", "t", "y", "1")
     false_set = ("no", "false", "f", "n", "0")
+
     if isinstance(value, str):
         value = value.lower()
         if value in true_set:
@@ -390,6 +399,38 @@ def str2bool(value: str, default: bool = False, raise_exc: bool = True) -> bool:
     return default
 
 
+def str2list(value: Optional[Union[str, list]], raise_exc: bool = True) -> Optional[list]:
+    """
+    Convert a string to a list.  Useful with argparse commandline arguments:
+        parser.add_argument("--blocks", default=[1,2,3], type=str2list)
+        python mycode.py --blocks=1,2,2,4
+
+    Args:
+        value: string (comma separated) to be converted to a list
+        raise_exc: if not possible to convert to a list, raise an exception
+    Raises
+        ValueError: value not a string or list or not possible to convert
+    """
+
+    if value is None:
+        return None
+    elif isinstance(value, list):
+        return value
+    elif isinstance(value, str):
+        v = value.split(",")
+        for i in range(len(v)):
+            try:
+                a = literal_eval(v[i].strip())  # attempt to convert
+                v[i] = a
+            except Exception:
+                pass
+        return v
+    elif raise_exc:
+        raise ValueError(f'Unable to convert "{value}", expected a comma-separated str, e.g. 1,2,3')
+
+    return None
+
+
 class MONAIEnvVars:
     """
     Environment variables used by MONAI.

tests/test_str2bool.py

@@ -16,9 +16,9 @@
 
 class TestStr2Bool(unittest.TestCase):
     def test_str_2_bool(self):
-        for i in ("yes", "true", "t", "y", "1"):
+        for i in ("yes", "true", "t", "y", "1", True):
             self.assertTrue(str2bool(i))
-        for i in ("no", "false", "f", "n", "0"):
+        for i in ("no", "false", "f", "n", "0", False):
             self.assertFalse(str2bool(i))
         for bad_value in ("test", 0, 1, 2, None):
             self.assertFalse(str2bool(bad_value, default=False, raise_exc=False))

tests/test_str2list.py

@@ -0,0 +1,30 @@
+# Copyright (c) MONAI Consortium
+# 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 unittest
+
+from monai.utils.misc import str2list
+
+
+class TestStr2List(unittest.TestCase):
+    def test_str_2_list(self):
+        for i in ("1,2,3", "1, 2, 3", "1,2e-0,3.0", [1, 2, 3]):
+            self.assertEqual(str2list(i), [1, 2, 3])
+        for i in ("1,2,3", "1,2,3,4.3", [1, 2, 3, 4.001]):
+            self.assertNotEqual(str2list(i), [1, 2, 3, 4])
+        for bad_value in ((1, 3), int):
+            self.assertIsNone(str2list(bad_value, raise_exc=False))
+            with self.assertRaises(ValueError):
+                self.assertIsNone(str2list(bad_value))
+
+
+if __name__ == "__main__":
+    unittest.main()