FilesystemBackend will now automatically create the directory given a…

…s its

argument if the new create_if_missing argument is explicitely turned to
True (False by default).

qctoolkit/serialization.py

@@ -106,18 +106,22 @@ class FilesystemBackend(StorageBackend):
 
     Data will be stored in plain text files in a directory. The directory is given in the
     constructor of this FilesystemBackend. For each data item, a separate file is created an named
-    after the corresponding identifier.
+    after the corresponding identifier. If the directory does not exist, it is not created unless the create_if_missing
+    argument is explicitly set to True.
     """
 
-    def __init__(self, root: str='.') -> None:
+    def __init__(self, root: str='.', create_if_missing: bool=False) -> None:
         """Create a new FilesystemBackend.
 
         Args:
             root: The path of the directory in which all data files are located. (default: ".",
                 i.e. the current directory)
+            create_if_missing: If False, do not create the specified directory if it does not exist. (default: False)
         Raises:
             NotADirectoryError: if root is not a valid directory path.
         """
+        if not os.path.exists(root) and create_if_missing:
+            os.makedirs(root)
         if not os.path.isdir(root):
             raise NotADirectoryError()
         self._root = os.path.abspath(root)

tests/serialization_tests.py

@@ -8,7 +8,7 @@
 from unittest import mock
 from abc import ABCMeta, abstractmethod
 
-from tempfile import TemporaryDirectory
+from tempfile import TemporaryDirectory, TemporaryFile
 from typing import Optional, Any, Dict, Tuple
 
 from qctoolkit.serialization import FilesystemBackend, CachingBackend, Serializable, JSONSerializableEncoder,\
@@ -265,6 +265,21 @@ def setUp(self) -> None:
     def tearDown(self) -> None:
         self.tmp_dir.cleanup()
 
+    def test_init_create_dir(self) -> None:
+        path = self.tmp_dir.name + "/inner_dir"
+        self.assertFalse(os.path.isdir(path))
+        with self.assertRaises(NotADirectoryError):
+            FilesystemBackend(path)
+            FilesystemBackend(path, create_if_missing=False)
+        self.assertFalse(os.path.isdir(path))
+        FilesystemBackend(path, create_if_missing=True)
+        self.assertTrue(os.path.isdir(path))
+
+    def test_init_file_path(self) -> None:
+        with TemporaryFile() as tmp_file:
+            with self.assertRaises(NotADirectoryError):
+                FilesystemBackend(tmp_file.name)
+
     def test_put_and_get_normal(self) -> None:
         # first put the data
         self.backend.put(self.identifier, self.test_data)