docs: python bindings howto

* Updated official doc (the org-mode file) with the instructions on
  importing and exporting both public and secret keys.

lang/python/docs/GPGMEpythonHOWTOen.org

@@ -454,6 +454,364 @@
    literals with the fingerprint when getting a key in this way.
 
 
+** Importing keys
+   :PROPERTIES:
+   :CUSTOM_ID: howto-import-key
+   :END:
+
+   Importing keys is possible with the =key_import()= method and takes
+   one argument which is a bytes literal object containing either the
+   binary or ASCII armoured key data for one or more keys.
+
+   The following example retrieves one or more keys from the SKS
+   keyservers via the web using the requests module. Since requests
+   returns the content as a bytes literal object, we can then use that
+   directly to import the resulting data into our keybox.
+
+   #+begin_src python
+     import gpg
+     import os.path
+     import requests
+
+     c = gpg.Context()
+     url = "https://sks-keyservers.net/pks/lookup"
+     pattern = input("Enter the pattern to search for key or user IDs: ")
+     payload = { "op": "get", "search": pattern }
+
+     r = requests.get(url, verify=True, params=payload)
+     result = c.key_import(r.content)
+
+     if result is not None and hasattr(result, "considered") is False:
+	 print(result)
+     elif result is not None and hasattr(result, "considered") is True:
+	 num_keys = len(result.imports)
+	 new_revs = result.new_revocations
+	 new_sigs = result.new_signatures
+	 new_subs = result.new_sub_keys
+	 new_uids = result.new_user_ids
+	 new_scrt = result.secret_imported
+	 nochange = result.unchanged
+	 print("""
+     The total number of keys considered for import was:  {0}
+
+	Number of keys revoked:  {1}
+      Number of new signatures:  {2}
+	 Number of new subkeys:  {3}
+	Number of new user IDs:  {4}
+     Number of new secret keys:  {5}
+      Number of unchanged keys:  {6}
+
+     The key IDs for all considered keys were:
+     """.format(num_keys, new_revs, new_sigs, new_subs, new_uids, new_scrt,
+		 nochange))
+	 for i in range(num_keys):
+	     print(result.imports[i].fpr)
+	 print("")
+     else:
+	 pass
+   #+end_src
+
+ *NOTE:* When searching for a key ID of any length or a fingerprint
+   (without spaces), the SKS servers require the the leading =0x=
+   indicative of hexadecimal be included. Also note that the old short
+   key IDs (e.g. =0xDEADBEEF=) should no longer be used due to the
+   relative ease by which such key IDs can be reproduced, as
+   demonstrated by the Evil32 Project in 2014 (which was subsequently
+   exploited in 2016).
+
+
+** Exporting keys
+   :PROPERTIES:
+   :CUSTOM_ID: howto-export-key
+   :END:
+
+   Exporting keys remains a reasonably simple task, but has been
+   separated into three different functions for the OpenPGP
+   cryptographic engine.  Two of those functions are for exporting
+   public keys and the third is for exporting secret keys.
+
+
+*** Exporting public keys
+    :PROPERTIES:
+    :CUSTOM_ID: howto-export-public-key
+    :END:
+
+    There are two methods of exporting public keys, both of which are
+    very similar to the other.  The default method, =key_export()=,
+    will export a public key or keys matching a specified pattern as
+    normal.  The alternative, the =key_export_minimal()= method, will
+    do the same thing except producing a minimised output with extra
+    signatures and third party signatures or certifications removed.
+
+    #+begin_src python
+      import gpg
+      import os.path
+      import sys
+
+      print("""
+      This script exports one or more public keys.
+      """)
+
+      c = gpg.Context(armor=True)
+
+      if len(sys.argv) >= 4:
+	  keyfile = sys.argv[1]
+	  logrus = sys.argv[2]
+	  homedir = sys.argv[3]
+      elif len(sys.argv) == 3:
+	  keyfile = sys.argv[1]
+	  logrus = sys.argv[2]
+	  homedir = input("Enter the GPG configuration directory path (optional): ")
+      elif len(sys.argv) == 2:
+	  keyfile = sys.argv[1]
+	  logrus = input("Enter the UID matching the key(s) to export: ")
+	  homedir = input("Enter the GPG configuration directory path (optional): ")
+      else:
+	  keyfile = input("Enter the path and filename to save the secret key to: ")
+	  logrus = input("Enter the UID matching the key(s) to export: ")
+	  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
+
+      try:
+	  result = c.key_export(pattern=logrus)
+      except:
+	  result = c.key_export(pattern=None)
+
+      if result is not None:
+	  with open(keyfile, "wb") as f:
+	      f.write(result)
+      else:
+	  pass
+    #+end_src
+
+    It is important to note that the result will only return =None=
+    when a pattern has been entered for =logrus=, but it has not
+    matched any keys. When the search pattern itself is set to =None=
+    this triggers the exporting of the entire public keybox.
+
+    #+begin_src python
+      import gpg
+      import os.path
+      import sys
+
+      print("""
+      This script exports one or more public keys in minimised form.
+      """)
+
+      c = gpg.Context(armor=True)
+
+      if len(sys.argv) >= 4:
+	  keyfile = sys.argv[1]
+	  logrus = sys.argv[2]
+	  homedir = sys.argv[3]
+      elif len(sys.argv) == 3:
+	  keyfile = sys.argv[1]
+	  logrus = sys.argv[2]
+	  homedir = input("Enter the GPG configuration directory path (optional): ")
+      elif len(sys.argv) == 2:
+	  keyfile = sys.argv[1]
+	  logrus = input("Enter the UID matching the key(s) to export: ")
+	  homedir = input("Enter the GPG configuration directory path (optional): ")
+      else:
+	  keyfile = input("Enter the path and filename to save the secret key to: ")
+	  logrus = input("Enter the UID matching the key(s) to export: ")
+	  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
+
+      try:
+	  result = c.key_export_minimal(pattern=logrus)
+      except:
+	  result = c.key_export_minimal(pattern=None)
+
+      if result is not None:
+	  with open(keyfile, "wb") as f:
+	      f.write(result)
+      else:
+	  pass
+    #+end_src
+
+
+*** Exporting secret keys
+    :PROPERTIES:
+    :CUSTOM_ID: howto-export-secret-key
+    :END:
+
+    Exporting secret keys is, functionally, very similar to exporting
+    public keys; save for the invocation of =pinentry= via =gpg-agent=
+    in order to securely enter the key's passphrase and authorise the
+    export.
+
+    The following example exports the secret key to a file which is
+    then set with the same permissions as the output files created by
+    the command line secret key export options.
+
+    #+begin_src python
+      import gpg
+      import os
+      import os.path
+      import sys
+
+      print("""
+      This script exports one or more secret keys.
+
+      The gpg-agent and pinentry are invoked to authorise the export.
+      """)
+
+      c = gpg.Context(armor=True)
+
+      if len(sys.argv) >= 4:
+	  keyfile = sys.argv[1]
+	  logrus = sys.argv[2]
+	  homedir = sys.argv[3]
+      elif len(sys.argv) == 3:
+	  keyfile = sys.argv[1]
+	  logrus = sys.argv[2]
+	  homedir = input("Enter the GPG configuration directory path (optional): ")
+      elif len(sys.argv) == 2:
+	  keyfile = sys.argv[1]
+	  logrus = input("Enter the UID matching the secret key(s) to export: ")
+	  homedir = input("Enter the GPG configuration directory path (optional): ")
+      else:
+	  keyfile = input("Enter the path and filename to save the secret key to: ")
+	  logrus = input("Enter the UID matching the secret key(s) to export: ")
+	  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
+
+      try:
+	  result = c.key_export_secret(pattern=logrus)
+      except:
+	  result = c.key_export_secret(pattern=None)
+
+      if result is not None:
+	  with open(keyfile, "wb") as f:
+	      f.write(result)
+	  os.chmod(keyfile, 0o600)
+      else:
+	  pass
+    #+end_src
+
+    Alternatively the approach of the following script can be
+    used.  This longer example saves the exported secret key(s) in
+    files in the GnuPG home directory, in addition to setting the file
+    permissions as only readable and writable by the user.  It also
+    exports the secret key(s) twice in order to output both GPG binary
+    (=.gpg=) and ASCII armoured (=.asc=) files.
+
+    #+begin_src python
+      import gpg
+      import os
+      import os.path
+      import subprocess
+      import sys
+
+      print("""
+      This script exports one or more secret keys as both ASCII armored and binary
+      file formats, saved in files within the user's GPG home directory.
+
+      The gpg-agent and pinentry are invoked to authorise the export.
+      """)
+
+      if sys.platform == "win32":
+	  gpgconfcmd = "gpgconf.exe --list-dirs homedir"
+      else:
+	  gpgconfcmd = "gpgconf --list-dirs homedir"
+
+      a = gpg.Context(armor=True)
+      b = gpg.Context()
+      c = gpg.Context()
+
+      if len(sys.argv) >= 4:
+	  keyfile = sys.argv[1]
+	  logrus = sys.argv[2]
+	  homedir = sys.argv[3]
+      elif len(sys.argv) == 3:
+	  keyfile = sys.argv[1]
+	  logrus = sys.argv[2]
+	  homedir = input("Enter the GPG configuration directory path (optional): ")
+      elif len(sys.argv) == 2:
+	  keyfile = sys.argv[1]
+	  logrus = input("Enter the UID matching the secret key(s) to export: ")
+	  homedir = input("Enter the GPG configuration directory path (optional): ")
+      else:
+	  keyfile = input("Enter the filename to save the secret key to: ")
+	  logrus = input("Enter the UID matching the secret key(s) to export: ")
+	  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
+
+      if c.home_dir is not None:
+	  if c.home_dir.endswith("/"):
+	      gpgfile = "{0}{1}.gpg".format(c.home_dir, keyfile)
+	      ascfile = "{0}{1}.asc".format(c.home_dir, keyfile)
+	  else:
+	      gpgfile = "{0}/{1}.gpg".format(c.home_dir, keyfile)
+	      ascfile = "{0}/{1}.asc".format(c.home_dir, keyfile)
+      else:
+	  if os.path.exists(os.environ["GNUPGHOME"]) is True:
+	      hd = os.environ["GNUPGHOME"]
+	  else:
+	      hd = subprocess.getoutput(gpgconfcmd)
+	  gpgfile = "{0}/{1}.gpg".format(hd, keyfile)
+	  ascfile = "{0}/{1}.asc".format(hd, keyfile)
+
+      try:
+	  a_result = a.key_export_secret(pattern=logrus)
+	  b_result = b.key_export_secret(pattern=logrus)
+      except:
+	  a_result = a.key_export_secret(pattern=None)
+	  b_result = b.key_export_secret(pattern=None)
+
+      if a_result is not None:
+	  with open(ascfile, "wb") as f:
+	      f.write(a_result)
+	  os.chmod(ascfile, 0o600)
+      else:
+	  pass
+
+      if b_result is not None:
+	  with open(gpgfile, "wb") as f:
+	      f.write(b_result)
+	  os.chmod(gpgfile, 0o600)
+      else:
+	  pass
+    #+end_src
+
+
 * Basic Functions
   :PROPERTIES:
   :CUSTOM_ID: howto-the-basics

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

@@ -0,0 +1,73 @@
+#!/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
+
+print("""
+This script exports one or more public keys.
+""")
+
+c = gpg.Context(armor=True)
+
+if len(sys.argv) >= 4:
+    keyfile = sys.argv[1]
+    logrus = sys.argv[2]
+    homedir = sys.argv[3]
+elif len(sys.argv) == 3:
+    keyfile = sys.argv[1]
+    logrus = sys.argv[2]
+    homedir = input("Enter the GPG configuration directory path (optional): ")
+elif len(sys.argv) == 2:
+    keyfile = sys.argv[1]
+    logrus = input("Enter the UID matching the key(s) to export: ")
+    homedir = input("Enter the GPG configuration directory path (optional): ")
+else:
+    keyfile = input("Enter the path and filename to save the secret key to: ")
+    logrus = input("Enter the UID matching the key(s) to export: ")
+    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
+
+try:
+    result = c.key_export(pattern=logrus)
+except:
+    result = c.key_export(pattern=None)
+
+if result is not None:
+    with open(keyfile, "wb") as f:
+        f.write(result)
+else:
+    pass

lang/python/examples/howto/export-minimised-key.py

@@ -0,0 +1,73 @@
+#!/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
+
+print("""
+This script exports one or more public keys in minimised form.
+""")
+
+c = gpg.Context(armor=True)
+
+if len(sys.argv) >= 4:
+    keyfile = sys.argv[1]
+    logrus = sys.argv[2]
+    homedir = sys.argv[3]
+elif len(sys.argv) == 3:
+    keyfile = sys.argv[1]
+    logrus = sys.argv[2]
+    homedir = input("Enter the GPG configuration directory path (optional): ")
+elif len(sys.argv) == 2:
+    keyfile = sys.argv[1]
+    logrus = input("Enter the UID matching the key(s) to export: ")
+    homedir = input("Enter the GPG configuration directory path (optional): ")
+else:
+    keyfile = input("Enter the path and filename to save the secret key to: ")
+    logrus = input("Enter the UID matching the key(s) to export: ")
+    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
+
+try:
+    result = c.key_export_minimal(pattern=logrus)
+except:
+    result = c.key_export_minimal(pattern=None)
+
+if result is not None:
+    with open(keyfile, "wb") as f:
+        f.write(result)
+else:
+    pass

lang/python/examples/howto/export-secret-key.py

@@ -0,0 +1,77 @@
+#!/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
+import os.path
+import sys
+
+print("""
+This script exports one or more secret keys.
+
+The gpg-agent and pinentry are invoked to authorise the export.
+""")
+
+c = gpg.Context(armor=True)
+
+if len(sys.argv) >= 4:
+    keyfile = sys.argv[1]
+    logrus = sys.argv[2]
+    homedir = sys.argv[3]
+elif len(sys.argv) == 3:
+    keyfile = sys.argv[1]
+    logrus = sys.argv[2]
+    homedir = input("Enter the GPG configuration directory path (optional): ")
+elif len(sys.argv) == 2:
+    keyfile = sys.argv[1]
+    logrus = input("Enter the UID matching the secret key(s) to export: ")
+    homedir = input("Enter the GPG configuration directory path (optional): ")
+else:
+    keyfile = input("Enter the path and filename to save the secret key to: ")
+    logrus = input("Enter the UID matching the secret key(s) to export: ")
+    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
+
+try:
+    result = c.key_export_secret(pattern=logrus)
+except:
+    result = c.key_export_secret(pattern=None)
+
+if result is not None:
+    with open(keyfile, "wb") as f:
+        f.write(result)
+    os.chmod(keyfile, 0o600)
+else:
+    pass

lang/python/examples/howto/export-secret-keys.py

@@ -0,0 +1,110 @@
+#!/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
+import os.path
+import subprocess
+import sys
+
+print("""
+This script exports one or more secret keys as both ASCII armored and binary
+file formats, saved in files within the user's GPG home directory.
+
+The gpg-agent and pinentry are invoked to authorise the export.
+""")
+
+if sys.platform == "win32":
+    gpgconfcmd = "gpgconf.exe --list-dirs homedir"
+else:
+    gpgconfcmd = "gpgconf --list-dirs homedir"
+
+a = gpg.Context(armor=True)
+b = gpg.Context()
+c = gpg.Context()
+
+if len(sys.argv) >= 4:
+    keyfile = sys.argv[1]
+    logrus = sys.argv[2]
+    homedir = sys.argv[3]
+elif len(sys.argv) == 3:
+    keyfile = sys.argv[1]
+    logrus = sys.argv[2]
+    homedir = input("Enter the GPG configuration directory path (optional): ")
+elif len(sys.argv) == 2:
+    keyfile = sys.argv[1]
+    logrus = input("Enter the UID matching the secret key(s) to export: ")
+    homedir = input("Enter the GPG configuration directory path (optional): ")
+else:
+    keyfile = input("Enter the filename to save the secret key to: ")
+    logrus = input("Enter the UID matching the secret key(s) to export: ")
+    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
+
+if c.home_dir is not None:
+    if c.home_dir.endswith("/"):
+        gpgfile = "{0}{1}.gpg".format(c.home_dir, keyfile)
+        ascfile = "{0}{1}.asc".format(c.home_dir, keyfile)
+    else:
+        gpgfile = "{0}/{1}.gpg".format(c.home_dir, keyfile)
+        ascfile = "{0}/{1}.asc".format(c.home_dir, keyfile)
+else:
+    if os.path.exists(os.environ["GNUPGHOME"]) is True:
+        hd = os.environ["GNUPGHOME"]
+    else:
+        hd = subprocess.getoutput(gpgconfcmd)
+    gpgfile = "{0}/{1}.gpg".format(hd, keyfile)
+    ascfile = "{0}/{1}.asc".format(hd, keyfile)
+
+try:
+    a_result = a.key_export_secret(pattern=logrus)
+    b_result = b.key_export_secret(pattern=logrus)
+except:
+    a_result = a.key_export_secret(pattern=None)
+    b_result = b.key_export_secret(pattern=None)
+
+if a_result is not None:
+    with open(ascfile, "wb") as f:
+        f.write(a_result)
+    os.chmod(ascfile, 0o600)
+else:
+    pass
+
+if b_result is not None:
+    with open(gpgfile, "wb") as f:
+        f.write(b_result)
+    os.chmod(gpgfile, 0o600)
+else:
+    pass

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

@@ -0,0 +1,91 @@
+#!/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
+
+print("""
+This script exports one or more public keys.
+""")
+
+c = gpg.Context(armor=True)
+
+if len(sys.argv) >= 3:
+    keyfile = sys.argv[1]
+    homedir = sys.argv[2]
+elif len(sys.argv) == 2:
+    keyfile = sys.argv[1]
+    homedir = input("Enter the GPG configuration directory path (optional): ")
+else:
+    keyfile = input("Enter the path and filename to import the key(s) from: ")
+    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
+
+if os.path.isfile(keyfile) is True:
+    with open(keyfile, "rb") as f:
+        incoming = f.read()
+    result = c.key_import(incoming)
+else:
+    result = None
+
+if result is not None and hasattr(result, "considered") is False:
+    print(result)
+elif result is not None and hasattr(result, "considered") is True:
+    num_keys = len(result.imports)
+    new_revs = result.new_revocations
+    new_sigs = result.new_signatures
+    new_subs = result.new_sub_keys
+    new_uids = result.new_user_ids
+    new_scrt = result.secret_imported
+    nochange = result.unchanged
+    print("""
+The total number of keys considered for import was:  {0}
+
+   Number of keys revoked:  {1}
+ Number of new signatures:  {2}
+    Number of new subkeys:  {3}
+   Number of new user IDs:  {4}
+Number of new secret keys:  {5}
+ Number of unchanged keys:  {6}
+
+The key IDs for all considered keys were:
+""".format(num_keys, new_revs, new_sigs, new_subs, new_uids, new_scrt,
+           nochange))
+    for i in range(num_keys):
+        print(result.imports[i].fpr)
+    print("")
+elif result is None:
+    print("You must specify a key file to import.")

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

@@ -0,0 +1,73 @@
+#!/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 requests
+
+print("""
+This script imports one or more public keys from the SKS keyservers.
+""")
+
+import gpg
+import requests
+
+c = gpg.Context()
+url = "https://sks-keyservers.net/pks/lookup"
+pattern = input("Enter the pattern to search for key or user IDs: ")
+payload = { "op": "get", "search": pattern }
+
+r = requests.get(url, verify=True, params=payload)
+result = c.key_import(r.content)
+
+if result is not None and hasattr(result, "considered") is False:
+    print(result)
+elif result is not None and hasattr(result, "considered") is True:
+    num_keys = len(result.imports)
+    new_revs = result.new_revocations
+    new_sigs = result.new_signatures
+    new_subs = result.new_sub_keys
+    new_uids = result.new_user_ids
+    new_scrt = result.secret_imported
+    nochange = result.unchanged
+    print("""
+The total number of keys considered for import was:  {0}
+
+   Number of keys revoked:  {1}
+ Number of new signatures:  {2}
+    Number of new subkeys:  {3}
+   Number of new user IDs:  {4}
+Number of new secret keys:  {5}
+ Number of unchanged keys:  {6}
+
+The key IDs for all considered keys were:
+""".format(num_keys, new_revs, new_sigs, new_subs, new_uids, new_scrt,
+           nochange))
+    for i in range(num_keys):
+        print(result.imports[i].fpr)
+    print("")
+else:
+    pass

lang/python/src/core.py

@@ -566,6 +566,116 @@ class Context(GpgmeWrapper):
 
         return import_result
 
+    def key_export(self, pattern=None):
+        """Export keys.
+
+        Exports public keys matching the pattern specified.  If no
+        pattern is specified then exports all available keys.
+
+        Keyword arguments:
+        pattern	-- return keys matching pattern (default: all keys)
+
+        Returns:
+                -- A key block containing one or more OpenPGP keys in
+                   either ASCII armoured or binary format as determined
+                   by the Context().  If there are no matching keys it
+                   returns None.
+
+        Raises:
+        GPGMEError     -- as signaled by the underlying library.
+        """
+        data = Data()
+        mode = 0
+        try:
+            self.op_export(pattern, mode, data)
+            data.seek(0, os.SEEK_SET)
+            pk_result = data.read()
+        except GPGMEError as e:
+            pk_result = e
+
+        if len(pk_result) > 0:
+            result = pk_result
+        else:
+            result = None
+
+        return result
+
+    def key_export_minimal(self, pattern=None):
+        """Export keys.
+
+        Exports public keys matching the pattern specified in a
+        minimised format.  If no pattern is specified then exports all
+        available keys.
+
+        Keyword arguments:
+        pattern	-- return keys matching pattern (default: all keys)
+
+        Returns: 
+                -- A key block containing one or more minimised OpenPGP
+                   keys in either ASCII armoured or binary format as 
+                   determined by the Context().  If there are no matching
+                   keys it returns None.
+
+        Raises:
+        GPGMEError     -- as signaled by the underlying library.
+        """
+        data = Data()
+        mode = gpgme.GPGME_EXPORT_MODE_MINIMAL
+        try:
+            self.op_export(pattern, mode, data)
+            data.seek(0, os.SEEK_SET)
+            pk_result = data.read()
+        except GPGMEError as e:
+            pk_result = e
+
+        if len(pk_result) > 0:
+            result = pk_result
+        else:
+            result = None
+
+        return result
+
+    def key_export_secret(self, pattern=None):
+        """Export secret keys.
+
+        Exports secret keys matching the pattern specified.  If no
+        pattern is specified then exports or attempts to export all
+        available secret keys.
+
+        IMPORTANT: Each secret key to be exported will prompt for its
+        passphrase via an invocation of pinentry and gpg-agent.  If the
+        passphrase is not entered or does not match then no data will be
+        exported.  This is the same result as when specifying a pattern
+        that is not matched by the available keys.
+
+        Keyword arguments:
+        pattern	-- return keys matching pattern (default: all keys)
+
+        Returns:
+                -- On success a key block containing one or more OpenPGP
+                   secret keys in either ASCII armoured or binary format
+                   as determined by the Context().
+                -- On failure while not raising an exception, returns None.
+
+        Raises:
+        GPGMEError     -- as signaled by the underlying library.
+        """
+        data = Data()
+        mode = gpgme.GPGME_EXPORT_MODE_SECRET
+        try:
+            self.op_export(pattern, mode, data)
+            data.seek(0, os.SEEK_SET)
+            sk_result = data.read()
+        except GPGMEError as e:
+            sk_result = e
+
+        if len(sk_result) > 0:
+            result = sk_result
+        else:
+            result = None
+
+        return result
+
     def keylist(self, pattern=None, secret=False,
                 mode=constants.keylist.mode.LOCAL,
                 source=None):