examples: python bindings howto

* Added a script for planned HOWTO expansion demonstrating key import
  from a file with optional alternative homedir setting.

lang/python/examples/howto/import-key.py

@@ -0,0 +1,75 @@
+#!/usr/bin/env python3
+# -*- coding: utf-8 -*-
+
+from __future__ import absolute_import, division, unicode_literals
+
+# Copyright (C) 2018 Ben McGinnes <ben@gnupg.org>
+#
+# This program is free software; you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free Software
+# Foundation; either version 2 of the License, or (at your option) any later
+# version.
+#
+# This program is free software; you can redistribute it and/or modify it under
+# the terms of the GNU Lesser General Public License as published by the Free
+# Software Foundation; either version 2.1 of the License, or (at your option)
+# any later version.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE.  See the GNU General Public License and the GNU
+# Lesser General Public Licensefor more details.
+#
+# You should have received a copy of the GNU General Public License and the GNU
+# Lesser General Public along with this program; if not, see
+# <http://www.gnu.org/licenses/>.
+
+import gpg
+import os.path
+import sys
+
+c = gpg.Context(armor=True)
+
+print("""
+This script imports a public key into the public keybox/keyring from a file.
+""")
+
+if len(sys.argv) >= 3:
+    filepth = sys.argv[1]
+    homedir = sys.argv[2]
+elif len(sys.argv) == 2:
+    filepth = sys.argv[1]
+    homedir = input("Enter the GPG configuration directory path (optional): ")
+else:
+    filepth = input("Enter the filename and path of the key file: ")
+    homedir = input("Enter the GPG configuration directory path (optional): ")
+
+if homedir.startswith("~"):
+    if os.path.exists(os.path.expanduser(homedir)) is True:
+        c.home_dir = os.path.expanduser(homedir)
+    else:
+        pass
+elif os.path.exists(homedir) is True:
+    c.home_dir = homedir
+else:
+    pass
+
+with open(filepth, "rb") as f:
+    incoming = f.read()
+
+c.op_import(incoming)
+res = c.op_import_result()
+
+result = """
+Imported {0} of {1} keys with:
+
+  {2} new revocations
+  {3} new signatures
+  {4} new sub keys
+  {5} new user IDs
+  {6} new secret keys
+  {7} unchanged keys
+""".format(res.imported, res.considered, res.new_revocations,
+           res.new_signatures, res.new_sub_keys, res.new_user_ids,
+           res.secret_imported, res.unchanged)
+print(res)