Add environment context manager, document it and test it

Author: acampove

README.md

@@ -52,6 +52,18 @@ Then, for each remote it pushes the tags and the commits.
 
 This section describes generic tools that could not be put in a specific category, but tend to be useful.
 
+## Environment
+
+To temporarily set an environment use:
+
+```python
+from dmu.generic import utilities as gut
+
+with gut.environment(mapping = {'VAR' : '1234', 'VOR' : 'abcd'}):
+    var = os.environ['VAR']
+    vor = os.environ['VOR']
+```
+
 ## Typing
 
 ### Pandas types

src/dmu/generic/utilities.py

@@ -83,6 +83,25 @@ def default_encoder(x):
     return json_string
 # ---------------------------------
 @contextmanager
+def environment(mapping : dict[str,str]):
+    '''
+    Parameters
+    ---------------
+    mapping: Dictionary holding environment that will be set
+    '''
+    old_mapping = { key : os.environ.get(key) for key in mapping }
+
+    try:
+        os.environ.update(mapping)
+        yield
+    finally:
+        for key, val in old_mapping.items():
+            if val is None:
+                os.environ.pop(key, None)
+            else:
+                os.environ[key] = val
+# ---------------------------------
+@contextmanager
 def enforce_schema_validation(value : bool):
     '''
     Parameters

tests/generic/test_generic_utilities.py

@@ -1,6 +1,7 @@
 '''
 Module with tests for functions in generic/utilities.py
 '''
+import os
 from time    import sleep
 from pathlib import Path
 
@@ -11,6 +12,23 @@
 
 log=LogStore.add_logger('dmu:test_generic_utilities')
 # ----------------------
+def test_environment_context():
+    '''
+    This function tests the environment context manager
+    '''
+    with gut.environment(mapping = {}):
+        pass
+
+    with gut.environment(mapping = {'VAR' : '1234'}):
+        assert os.environ['VAR'] == '1234'
+    
+    with gut.environment(mapping = {'VAR' : '1234', 'VOR' : 'abcd'}):
+        assert os.environ['VAR'] == '1234'
+        assert os.environ['VOR'] == 'abcd'
+
+    with pytest.raises(KeyError):
+        os.environ['VAR']
+# ----------------------
 @pytest.fixture(scope='session', autouse=True)
 def initialize():
     '''