diff --git a/ebook_converter/__init__.py b/ebook_converter/__init__.py
index c920e9f..3af6217 100644
--- a/ebook_converter/__init__.py
+++ b/ebook_converter/__init__.py
@@ -1,8 +1,3 @@
-''' E-book management software'''
-__license__ = 'GPL v3'
-__copyright__ = '2008, Kovid Goyal <kovid@kovidgoyal.net>'
-__docformat__ = 'restructuredtext en'
-
 import math
 import os
 import pkg_resources
@@ -14,7 +9,7 @@ import urllib.parse
 import urllib.request
 import warnings
 
-from ebook_converter.polyglot.builtins import hasenv, native_string_type
+from ebook_converter.polyglot.builtins import hasenv
 from functools import partial
 
 if not hasenv('CALIBRE_SHOW_DEPRECATION_WARNINGS'):
@@ -191,10 +186,6 @@ def prints(*args, **kwargs):
                         raise
                     arg = repr(arg)
         if not isinstance(arg, bytes):
-            try:
-                arg = native_string_type(arg)
-            except ValueError:
-                arg = str(arg)
             if isinstance(arg, str):
                 try:
                     arg = arg.encode(enc)
@@ -612,10 +603,7 @@ def as_unicode(obj, enc=preferred_encoding):
         try:
             obj = str(obj)
         except Exception:
-            try:
-                obj = native_string_type(obj)
-            except Exception:
-                obj = repr(obj)
+            obj = repr(obj)
     return force_unicode(obj, enc=enc)
 
 
diff --git a/ebook_converter/constants.py b/ebook_converter/constants.py
index 654a295..2abc793 100644
--- a/ebook_converter/constants.py
+++ b/ebook_converter/constants.py
@@ -5,7 +5,7 @@ import locale
 import os
 import sys
 
-from ebook_converter.polyglot.builtins import environ_item, hasenv, as_unicode, native_string_type
+from ebook_converter.polyglot.builtins import environ_item, hasenv, as_unicode
 
 __appname__   = 'calibre'
 numeric_version = (4, 12, 0)
@@ -178,7 +178,7 @@ class Plugins(collections.Mapping):
             try:
                 plugin_err = str(err)
             except Exception:
-                plugin_err = as_unicode(native_string_type(err), encoding=preferred_encoding, errors='replace')
+                plugin_err = as_unicode(err, encoding=preferred_encoding, errors='replace')
         self._plugins[name] = p, plugin_err
         # sys.path.remove(plugins_loc)
 
diff --git a/ebook_converter/ebooks/conversion/__init__.py b/ebook_converter/ebooks/conversion/__init__.py
index 944e1e7..8e83c72 100644
--- a/ebook_converter/ebooks/conversion/__init__.py
+++ b/ebook_converter/ebooks/conversion/__init__.py
@@ -1,11 +1,3 @@
-from ebook_converter.polyglot.builtins import native_string_type
-
-
-__license__ = 'GPL v3'
-__copyright__ = '2011, Kovid Goyal <kovid@kovidgoyal.net>'
-__docformat__ = 'restructuredtext en'
-
-
 class ConversionUserFeedBack(Exception):
 
     def __init__(self, title, msg, level='info', det_msg=''):
@@ -25,4 +17,4 @@ class ConversionUserFeedBack(Exception):
 
 # Ensure exception uses fully qualified name as this is used to detect it in
 # the GUI.
-ConversionUserFeedBack.__name__ = native_string_type('ebook_converter.ebooks.conversion.ConversionUserFeedBack')
+ConversionUserFeedBack.__name__ = 'ebook_converter.ebooks.conversion.ConversionUserFeedBack'
diff --git a/ebook_converter/ebooks/docx/fields.py b/ebook_converter/ebooks/docx/fields.py
index 09b5d2f..ce53800 100644
--- a/ebook_converter/ebooks/docx/fields.py
+++ b/ebook_converter/ebooks/docx/fields.py
@@ -1,11 +1,6 @@
 import re
 
 from ebook_converter.ebooks.docx.index import process_index, polish_index_markup
-from ebook_converter.polyglot.builtins import native_string_type
-
-
-__license__ = 'GPL v3'
-__copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 
 
 class Field(object):
@@ -72,7 +67,7 @@ def parser(name, field_map, default_field_name=None):
         ans.pop(null, None)
         return ans
 
-    parse.__name__ = native_string_type('parse_' + name)
+    parse.__name__ = 'parse_' + name
 
     return parse
 
diff --git a/ebook_converter/ebooks/docx/writer/container.py b/ebook_converter/ebooks/docx/writer/container.py
index 1794dc5..46d6e0c 100644
--- a/ebook_converter/ebooks/docx/writer/container.py
+++ b/ebook_converter/ebooks/docx/writer/container.py
@@ -11,11 +11,6 @@ from ebook_converter.ebooks.pdf.render.common import PAPER_SIZES
 from ebook_converter.utils.date import utcnow
 from ebook_converter.utils.localization import canonicalize_lang, lang_as_iso639_1
 from ebook_converter.utils.zipfile import ZipFile
-from ebook_converter.polyglot.builtins import native_string_type
-
-
-__license__ = 'GPL v3'
-__copyright__ = '2013, Kovid Goyal <kovid at kovidgoyal.net>'
 
 
 def xml2str(root, pretty_print=False, with_tail=False):
@@ -237,7 +232,7 @@ class DOCX(object):
         namespaces = self.namespace.namespaces
         E = ElementMaker(namespace=namespaces['cp'], nsmap={x:namespaces[x] for x in 'cp dc dcterms xsi'.split()})
         cp = E.coreProperties(E.revision("1"), E.lastModifiedBy('calibre'))
-        ts = utcnow().isoformat(native_string_type('T')).rpartition('.')[0] + 'Z'
+        ts = utcnow().isoformat('T').rpartition('.')[0] + 'Z'
         for x in 'created modified'.split():
             x = cp.makeelement('{%s}%s' % (namespaces['dcterms'], x), **{'{%s}type' % namespaces['xsi']:'dcterms:W3CDTF'})
             x.text = ts
diff --git a/ebook_converter/ebooks/lrf/html/table.py b/ebook_converter/ebooks/lrf/html/table.py
index ca41acc..c305da9 100644
--- a/ebook_converter/ebooks/lrf/html/table.py
+++ b/ebook_converter/ebooks/lrf/html/table.py
@@ -4,11 +4,6 @@ from ebook_converter.ebooks.lrf.fonts import get_font
 from ebook_converter.ebooks.lrf.pylrs.pylrs import TextBlock, Text, CR, Span, \
                                              CharButton, Plot, Paragraph, \
                                              LrsTextTag
-from ebook_converter.polyglot.builtins import native_string_type
-
-
-__license__ = 'GPL v3'
-__copyright__ = '2008, Kovid Goyal <kovid at kovidgoyal.net>'
 
 
 def ceil(num):
@@ -17,8 +12,8 @@ def ceil(num):
 
 def print_xml(elem):
     from ebook_converter.ebooks.lrf.pylrs.pylrs import ElementWriter
-    elem = elem.toElement(native_string_type('utf8'))
-    ew = ElementWriter(elem, sourceEncoding=native_string_type('utf8'))
+    elem = elem.toElement('utf8')
+    ew = ElementWriter(elem, sourceEncoding='utf8')
     ew.write(sys.stdout)
     print()
 
diff --git a/ebook_converter/ebooks/lrf/pylrs/pylrs.py b/ebook_converter/ebooks/lrf/pylrs/pylrs.py
index bcbd057..20e6f0f 100644
--- a/ebook_converter/ebooks/lrf/pylrs/pylrs.py
+++ b/ebook_converter/ebooks/lrf/pylrs/pylrs.py
@@ -51,7 +51,6 @@ DEFAULT_GENREADING      = "fs"          # default is yes to both lrf and lrs
 
 from ebook_converter import __appname__, __version__
 from ebook_converter import entity_to_unicode
-from ebook_converter.polyglot.builtins import native_string_type
 
 
 class LrsError(Exception):
@@ -617,7 +616,7 @@ class Book(Delegator):
 
         _formatXml(root)
         tree = ElementTree(element=root)
-        tree.write(f, encoding=native_string_type(outputEncodingName), xml_declaration=True)
+        tree.write(f, encoding=outputEncodingName, xml_declaration=True)
 
 
 class BookInformation(Delegator):
@@ -669,7 +668,7 @@ class Info(Delegator):
         # NB: generates an encoding attribute, which lrs2lrf does not
         tree = ElementTree(element=info)
         f = io.BytesIO()
-        tree.write(f, encoding=native_string_type('utf-8'), xml_declaration=True)
+        tree.write(f, encoding='utf-8', xml_declaration=True)
         xmlInfo = f.getvalue().decode('utf-8')
         xmlInfo = re.sub(r"<CThumbnail.*?>\n", "", xmlInfo)
         xmlInfo = xmlInfo.replace("SumPage>", "Page>")
diff --git a/ebook_converter/ebooks/metadata/pdf.py b/ebook_converter/ebooks/metadata/pdf.py
index aff4f9c..85da406 100644
--- a/ebook_converter/ebooks/metadata/pdf.py
+++ b/ebook_converter/ebooks/metadata/pdf.py
@@ -9,7 +9,6 @@ from ebook_converter.constants import iswindows
 from ebook_converter.ptempfile import TemporaryDirectory
 from ebook_converter.ebooks.metadata import (
     MetaInformation, string_to_authors, check_isbn, check_doi)
-from ebook_converter.utils.ipc.simple_worker import fork_job, WorkerError
 
 
 __license__ = 'GPL v3'
diff --git a/ebook_converter/polyglot/builtins.py b/ebook_converter/polyglot/builtins.py
index 48af640..204e464 100644
--- a/ebook_converter/polyglot/builtins.py
+++ b/ebook_converter/polyglot/builtins.py
@@ -2,10 +2,6 @@ import importlib
 import os
 
 
-native_string_type = str
-iterkeys = iter
-
-
 def hasenv(x):
     return os.getenv(x) is not None
 
diff --git a/ebook_converter/utils/config.py b/ebook_converter/utils/config.py
index 6d48a86..71b5d70 100644
--- a/ebook_converter/utils/config.py
+++ b/ebook_converter/utils/config.py
@@ -14,12 +14,6 @@ from ebook_converter.utils.config_base import (
     tweaks, from_json, to_json
 )
 from ebook_converter.utils.lock import ExclusiveFile
-from ebook_converter.polyglot.builtins import native_string_type
-
-
-__license__ = 'GPL v3'
-__copyright__ = '2008, Kovid Goyal kovid@kovidgoyal.net'
-__docformat__ = 'restructuredtext en'
 
 
 # optparse uses gettext.gettext instead of _ from builtins, so we
@@ -164,11 +158,11 @@ class OptionParser(optparse.OptionParser):
 
     def options_iter(self):
         for opt in self.option_list:
-            if native_string_type(opt).strip():
+            if str(opt).strip():
                 yield opt
         for gr in self.option_groups:
             for opt in gr.option_list:
-                if native_string_type(opt).strip():
+                if str(opt).strip():
                     yield opt
 
     def option_by_dest(self, dest):
@@ -193,7 +187,6 @@ class OptionParser(optparse.OptionParser):
     def add_option_group(self, *args, **kwargs):
         if isinstance(args[0], (str, bytes)):
             args = list(args)
-            args[0] = native_string_type(args[0])
         return optparse.OptionParser.add_option_group(self, *args, **kwargs)
 
 
diff --git a/ebook_converter/utils/date.py b/ebook_converter/utils/date.py
index de5c6a7..34ee7c0 100644
--- a/ebook_converter/utils/date.py
+++ b/ebook_converter/utils/date.py
@@ -6,13 +6,8 @@ from ebook_converter import strftime
 from ebook_converter.constants import iswindows, isosx, plugins, preferred_encoding
 from ebook_converter.utils.iso8601 import utc_tz, local_tz, UNDEFINED_DATE
 from ebook_converter.utils.localization import lcdata
-from ebook_converter.polyglot.builtins import native_string_type
 
 
-__license__ = 'GPL v3'
-__copyright__ = '2010, Kovid Goyal <kovid@kovidgoyal.net>'
-__docformat__ = 'restructuredtext en'
-
 _utc_tz = utc_tz
 _local_tz = local_tz
 
@@ -39,7 +34,7 @@ else:
         def first_index(raw, queries):
             for q in queries:
                 try:
-                    return raw.index(native_string_type(q))
+                    return raw.index(q)
                 except ValueError:
                     pass
             return -1
@@ -191,8 +186,7 @@ def isoformat(date_time, assume_utc=False, as_utc=True, sep='T'):
         date_time = date_time.replace(tzinfo=_utc_tz if assume_utc else
                 _local_tz)
     date_time = date_time.astimezone(_utc_tz if as_utc else _local_tz)
-    # native_string_type(sep) because isoformat barfs with unicode sep on python 2.x
-    return str(date_time.isoformat(native_string_type(sep)))
+    return str(date_time.isoformat(sep))
 
 
 def internal_iso_format_string():
diff --git a/ebook_converter/utils/ipc/launch.py b/ebook_converter/utils/ipc/launch.py
index 689734b..1d05662 100644
--- a/ebook_converter/utils/ipc/launch.py
+++ b/ebook_converter/utils/ipc/launch.py
@@ -5,7 +5,7 @@ from ebook_converter.constants import isosx, isfrozen, filesystem_encoding
 from ebook_converter.utils.config import prefs
 from ebook_converter.ptempfile import PersistentTemporaryFile, base_dir
 from ebook_converter.utils.serialize import msgpack_dumps
-from ebook_converter.polyglot.builtins import environ_item, native_string_type
+from ebook_converter.polyglot.builtins import environ_item
 from ebook_converter.polyglot.binary import as_hex_unicode
 try:
     import win32process
@@ -14,11 +14,6 @@ except ImportError:
     iswindows = False
 
 
-__license__ = 'GPL v3'
-__copyright__ = '2009, Kovid Goyal <kovid@kovidgoyal.net>'
-__docformat__ = 'restructuredtext en'
-
-
 if iswindows:
     try:
         windows_null_file = open(os.devnull, 'wb')
@@ -89,9 +84,9 @@ class Worker(object):
     @property
     def env(self):
         env = os.environ.copy()
-        env[native_string_type('CALIBRE_WORKER')] = environ_item('1')
+        env['CALIBRE_WORKER'] = environ_item('1')
         td = as_hex_unicode(msgpack_dumps(base_dir()))
-        env[native_string_type('CALIBRE_WORKER_TEMP_DIR')] = environ_item(td)
+        env['CALIBRE_WORKER_TEMP_DIR'] = environ_item(td)
         env.update(self._env)
         return env
 
@@ -154,7 +149,7 @@ class Worker(object):
         except EnvironmentError:
             # cwd no longer exists
             origwd = cwd or os.path.expanduser('~')
-        env[native_string_type('ORIGWD')] = environ_item(as_hex_unicode(msgpack_dumps(origwd)))
+        env['ORIGWD'] = environ_item(as_hex_unicode(msgpack_dumps(origwd)))
         _cwd = cwd
         if priority is None:
             priority = prefs['worker_process_priority']
diff --git a/ebook_converter/utils/terminal.py b/ebook_converter/utils/terminal.py
index 75a5597..302d31f 100644
--- a/ebook_converter/utils/terminal.py
+++ b/ebook_converter/utils/terminal.py
@@ -6,13 +6,6 @@ try:
 except ValueError:
     iswindows = False
 
-from ebook_converter.polyglot.builtins import native_string_type
-
-
-__license__ = 'GPL v3'
-__copyright__ = '2012, Kovid Goyal <kovid at kovidgoyal.net>'
-__docformat__ = 'restructuredtext en'
-
 
 def fmt(code):
     return '\033[%dm' % code
@@ -128,7 +121,7 @@ class Detect(object):
                     # Stream is a console
                     self.set_console = windll.kernel32.SetConsoleTextAttribute
                     self.default_console_text_attributes = WCOLORS['white']
-                    kernel32 = WinDLL(native_string_type('kernel32'), use_last_error=True)
+                    kernel32 = WinDLL('kernel32', use_last_error=True)
                     self.write_console = kernel32.WriteConsoleW
                     self.write_console.argtypes = [wintypes.HANDLE, wintypes.c_wchar_p, wintypes.DWORD, POINTER(wintypes.DWORD), wintypes.LPVOID]
                     self.write_console.restype = wintypes.BOOL