command line based loading of configs

bob/learn/tensorflow/utils/__init__.py

 from .util import *
 from .singleton import Singleton
-from .session import Session
\ No newline at end of file
+from .session import Session
+from . import commandline
\ No newline at end of file

bob/learn/tensorflow/utils/commandline.py

+def get_from_config_or_commandline(config, keyword, args, defaults,
+                                   default_is_valid=True):
+    """Takes the value from command line, config file, and default value with
+    this precedence.
+
+    Only several command line options can be used with this function:
+    - boolean flags
+    - repeating flags (like --verbose)
+    - options where the user will never provide the default value through
+      command line. For example when [default: None]
+
+    Parameters
+    ----------
+    config : object
+        The loaded config files.
+    keyword : str
+        The keyword to load from the config file or through command line.
+    args : dict
+        The arguments parsed with docopt.
+    defaults : dict
+        The arguments parsed with docopt when ``argv=[]``.
+    default_is_valid : bool, optional
+        If False, will raise an exception if the final parsed value is the
+        default value.
+
+    Returns
+    -------
+    object
+        The bool or integer value of the corresponding keyword.
+
+    Example
+    -------
+    >>> from bob.bio.base.utils import read_config_file
+    >>> defaults = docopt(docs, argv=[""])
+    >>> args = docopt(docs, argv=argv)
+    >>> config_files = args['<config_files>']
+    >>> config = read_config_file(config_files)
+
+    >>> verbosity = get_from_config_or_commandline(config, 'verbose', args,
+    ...                                            defaults)
+
+    """
+    arg_keyword = '--' + keyword.replace('_', '-')
+
+    # load from config first
+    value = getattr(config, keyword, defaults[arg_keyword])
+
+    # override it if provided by command line arguments
+    if args[arg_keyword] != defaults[arg_keyword]:
+        value = args[arg_keyword]
+
+    if not default_is_valid and value == defaults[arg_keyword]:
+        raise ValueError(
+            "The value provided for {} is not valid.".format(keyword))
+
+    return value