add arghelper lib

libs/arghelper.py

@@ -0,0 +1,116 @@
+#!/usr/bin/env python
+# -*- coding: utf-8 -*-
+# Copyright (c) 2014-2016 The arghelper developers. All rights reserved.
+# Project site: https://github.com/questrail/arghelper
+# Use of this source code is governed by a MIT-style license that
+# can be found in the LICENSE.txt file for the project.
+"""Provide helper functions for argparse
+
+"""
+
+# Try to future proof code so that it's Python 3.x ready
+from __future__ import print_function
+from __future__ import unicode_literals
+from __future__ import division
+from __future__ import absolute_import
+
+# Standard module imports
+import argparse
+import sys
+import os
+
+
+def extant_file(arg):
+    """Facade for extant_item(arg, arg_type="file")
+    """
+    return extant_item(arg, "file")
+
+
+def extant_dir(arg):
+    """Facade for extant_item(arg, arg_type="directory")
+    """
+    return extant_item(arg, "directory")
+
+
+def extant_item(arg, arg_type):
+    """Determine if parser argument is an existing file or directory.
+
+    This technique comes from http://stackoverflow.com/a/11541450/95592
+    and from http://stackoverflow.com/a/11541495/95592
+
+    Args:
+        arg: parser argument containing filename to be checked
+        arg_type: string of either "file" or "directory"
+
+    Returns:
+        If the file exists, return the filename or directory.
+
+    Raises:
+        If the file does not exist, raise a parser error.
+    """
+    if arg_type == "file":
+        if not os.path.isfile(arg):
+            raise argparse.ArgumentError(
+                None,
+                "The file {arg} does not exist.".format(arg=arg))
+        else:
+            # File exists so return the filename
+            return arg
+    elif arg_type == "directory":
+        if not os.path.isdir(arg):
+            raise argparse.ArgumentError(
+                None,
+                "The directory {arg} does not exist.".format(arg=arg))
+        else:
+            # Directory exists so return the directory name
+            return arg
+
+
+def parse_config_input_output(args=sys.argv):
+    """Parse the args using the config_file, input_dir, output_dir pattern
+
+    Args:
+        args: sys.argv
+
+    Returns:
+        The populated namespace object from parser.parse_args().
+
+    Raises:
+        TBD
+    """
+    parser = argparse.ArgumentParser(
+        description='Process the input files using the given config')
+    parser.add_argument(
+        'config_file',
+        help='Configuration file.',
+        metavar='FILE', type=extant_file)
+    parser.add_argument(
+        'input_dir',
+        help='Directory containing the input files.',
+        metavar='DIR', type=extant_dir)
+    parser.add_argument(
+        'output_dir',
+        help='Directory where the output files should be saved.',
+        metavar='DIR', type=extant_dir)
+    return parser.parse_args(args[1:])
+
+
+def parse_config(args=sys.argv):
+    """Parse the args using the config_file pattern
+
+    Args:
+        args: sys.argv
+
+    Returns:
+        The populated namespace object from parser.parse_args().
+
+    Raises:
+        TBD
+    """
+    parser = argparse.ArgumentParser(
+        description='Read in the config file')
+    parser.add_argument(
+        'config_file',
+        help='Configuration file.',
+        metavar='FILE', type=extant_file)
+    return parser.parse_args(args[1:])