helper function for configuration update from environment variables

common_helper_files/__init__.py

@@ -2,6 +2,7 @@ from .file_functions import read_in_chunks, get_directory_for_filename, create_d
 from .git_functions import get_version_string_from_git
 from .hash_functions import md5sum
 from .fail_safe_file_operations import get_binary_from_file, write_binary_to_file, get_safe_name, delete_file, get_files_in_dir
+from .config_functions import update_config_from_env
 
 __all__ = [
     'get_directory_for_filename',
@@ -14,5 +15,6 @@ __all__ = [
     'write_binary_to_file',
     'get_safe_name',
     'delete_file',
-    'get_files_in_dir'
+    'get_files_in_dir',
+    'update_config_from_env',
 ]

common_helper_files/config_functions.py

+"""Helper functions for configuration files.
+"""
+import os
+import logging
+
+log = logging.getLogger(__name__)
+
+
+def update_config_from_env(config):
+    """ Update configuration fields in config from environment variables.
+
+    The environment variable names are expected to be of the form, that the
+    section name and the variable name are seperated by a dubble underscore,
+    e.g.
+
+        SECTION_NAME__VARIABLE_NAME
+
+    """
+    for key, val in os.environ.items():
+        if '__' in key:
+            section, section_key = key.lower().split('__')
+            try:
+                config[section.capitalize()][section_key] = val
+            except KeyError:
+                log.error('No section {} or value {} found.'.format(section.capitalize(), section_key))
+
+    return config