Remove all support for Python 2

CHANGES.rst

@@ -5,6 +5,8 @@
 
 - ICRSCoord tag has moved to Astropy core package. [#401]
 
+- Remove support for Python 2. [#409]
+
 1.4.0 (unreleased)
 ------------------
 

asdf/__init__.py

@@ -1,7 +1,6 @@
 # Licensed under a 3-clause BSD style license - see LICENSE.rst
 # -*- coding: utf-8 -*-
 
-from __future__ import absolute_import, division, unicode_literals, print_function
 
 """
 asdf: Python library for reading and writing Advanced Scientific

asdf/_internal_init.py

@@ -1,7 +1,6 @@
 # Licensed under a 3-clause BSD style license - see LICENSE.rst
 # -*- coding: utf-8 -*-
 
-from __future__ import absolute_import, division, unicode_literals, print_function
 
 __all__ = ['__version__', '__githash__', 'test']
 

asdf/asdf.py

@@ -1,7 +1,6 @@
 # Licensed under a 3-clause BSD style license - see LICENSE.rst
 # -*- coding: utf-8 -*-
 
-from __future__ import absolute_import, division, unicode_literals, print_function
 
 import io
 import re

asdf/asdftypes.py

@@ -1,7 +1,6 @@
 # Licensed under a 3-clause BSD style license - see LICENSE.rst
 # -*- coding: utf-8 -*-
 
-from __future__ import absolute_import, division, unicode_literals, print_function
 
 import bisect
 import importlib
@@ -11,7 +10,7 @@
 import six
 from copy import copy
 
-from .compat import lru_cache
+from functools import lru_cache
 
 from . import tagged
 from . import util
@@ -21,9 +20,7 @@
 __all__ = ['format_tag', 'AsdfTypeIndex', 'AsdfType']
 
 
-_BASIC_PYTHON_TYPES = set(list(six.string_types) +
-                          list(six.integer_types) +
-                          [float, list, dict, tuple])
+_BASIC_PYTHON_TYPES = [str, int, float, list, dict, tuple]
 
 # regex used to parse module name from optional version string
 MODULE_RE = re.compile(r'([a-zA-Z]+)(-(\d+\.\d+\.\d+))?')
@@ -104,7 +101,7 @@ def add_by_tag(name, version):
                 add_type(asdftype)
 
         if self._version == 'latest':
-            for name, versions in six.iteritems(index._versions_by_type_name):
+            for name, versions in index._versions_by_type_name.items():
                 add_by_tag(name, versions[-1])
         else:
             try:
@@ -114,11 +111,11 @@ def add_by_tag(name, version):
                     "Don't know how to write out ASDF version {0}".format(
                         self._version))
 
-            for name, _version in six.iteritems(version_map['tags']):
+            for name, _version in version_map['tags'].items():
                 add_by_tag(name, AsdfVersion(_version))
 
             # Now add any extension types that aren't known to the ASDF standard
-            for name, versions in six.iteritems(index._versions_by_type_name):
+            for name, versions in index._versions_by_type_name.items():
                 if name not in self._type_by_name:
                     add_by_tag(name, versions[-1])
 
@@ -143,8 +140,7 @@ def from_custom_type(self, custom_type):
                 # includes classes that are created dynamically post
                 # Python-import, e.g. astropy.modeling._CompoundModel
                 # subclasses.
-                for key, val in six.iteritems(
-                        self._types_with_dynamic_subclasses):
+                for key, val in self._types_with_dynamic_subclasses.items():
                     if issubclass(custom_type, key):
                         self._type_by_cls[custom_type] = val
                         return val
@@ -178,7 +174,7 @@ def add_type(self, asdftype):
 
         if isinstance(asdftype.name, list):
             yaml_tags = [asdftype.make_yaml_tag(name) for name in asdftype.name]
-        elif isinstance(asdftype.name, six.string_types):
+        elif isinstance(asdftype.name, str):
             yaml_tags = [asdftype.yaml_tag]
         elif asdftype.name is None:
             yaml_tags = []
@@ -413,7 +409,7 @@ def __new__(mcls, name, bases, attrs):
             types = mcls._find_in_bases(attrs, bases, 'types', [])
             new_types = []
             for typ in types:
-                if isinstance(typ, six.string_types):
+                if isinstance(typ, str):
                     typ = util.resolve_name(typ)
                 new_types.append(typ)
             attrs['types'] = new_types
@@ -425,7 +421,7 @@ def __new__(mcls, name, bases, attrs):
                 cls.version = AsdfVersion(cls.version)
 
         if hasattr(cls, 'name'):
-            if isinstance(cls.name, six.string_types):
+            if isinstance(cls.name, str):
                 if 'yaml_tag' not in attrs:
                     cls.yaml_tag = cls.make_yaml_tag(cls.name)
             elif isinstance(cls.name, list):

asdf/block.py

@@ -1,22 +1,18 @@
 # Licensed under a 3-clause BSD style license - see LICENSE.rst
 # -*- coding: utf-8 -*-
 
-from __future__ import absolute_import, division, unicode_literals, print_function
-
-from collections import namedtuple
 import copy
 import hashlib
 import io
 import os
 import re
 import struct
 import weakref
+from collections import namedtuple
+from urllib import parse as urlparse
 
 import numpy as np
 
-import six
-from six.moves.urllib import parse as urlparse
-
 import yaml
 
 from . import compression as mcompression
@@ -472,7 +468,7 @@ def read_block_index(self, fd, ctx):
 
         last_offset = 0
         for x in offsets:
-            if (not isinstance(x, six.integer_types) or
+            if (not isinstance(x, int) or
                 x > file_size or
                 x < 0 or
                 x <= last_offset + Block._header.size):
@@ -592,7 +588,7 @@ def get_block(self, source):
         buffer : buffer
         """
         # If an "int", it is the index of an internal block
-        if isinstance(source, six.integer_types):
+        if isinstance(source, int):
             if source == -1:
                 if len(self._streamed_blocks):
                     return self._streamed_blocks[0]
@@ -639,7 +635,7 @@ def get_block(self, source):
 
             raise ValueError("Block '{0}' not found.".format(source))
 
-        elif isinstance(source, six.string_types):
+        elif isinstance(source, str):
             asdffile = self._asdffile().open_external(
                 source, do_not_fill_defaults=True)
             block = asdffile.blocks._internal_blocks[0]
@@ -901,10 +897,8 @@ def update_size(self):
         updating the file in-place, otherwise the work is redundant.
         """
         if self._data is not None:
-            if six.PY2: # pragma: no cover
-                self._data_size = len(self._data.data)
-            else:
-                self._data_size = self._data.data.nbytes
+            self._data_size = self._data.data.nbytes
+
             if not self.output_compression:
                 self._size = self._data_size
             else:

asdf/commands/__init__.py

@@ -1,7 +1,6 @@
 # Licensed under a 3-clause BSD style license - see LICENSE.rst
 # -*- coding: utf-8 -*-
 
-from __future__ import absolute_import, division, unicode_literals, print_function
 
 from .exploded import *
 from .to_yaml import *

asdf/commands/defragment.py

@@ -5,7 +5,6 @@
 Defragment command.
 """
 
-from __future__ import absolute_import, division, unicode_literals, print_function
 
 import os
 

asdf/commands/diff.py

@@ -5,7 +5,6 @@
 Implementation of command for displaying differences between two ASDF files.
 """
 
-from __future__ import absolute_import, division, unicode_literals, print_function
 
 import os
 import sys

asdf/commands/exploded.py

@@ -5,7 +5,6 @@
 Contains commands for dealing with exploded and imploded forms.
 """
 
-from __future__ import absolute_import, division, unicode_literals, print_function
 
 import os
 

asdf/commands/main.py

@@ -1,15 +1,10 @@
 # -*- coding: utf-8 -*-
 # Licensed under a 3-clause BSD style license - see LICENSE.rst
 
-from __future__ import (absolute_import, division, print_function,
-                        unicode_literals)
-
 import argparse
 import logging
 import sys
 
-import six
-
 from .. import util
 
 
@@ -61,7 +56,7 @@ def help(args):
         commands[str(command)].setup_arguments(subparsers)
         del commands[command]
 
-    for name, command in sorted(six.iteritems(commands)):
+    for name, command in sorted(commands.items()):
         command.setup_arguments(subparsers)
 
     return parser, subparsers
@@ -80,10 +75,10 @@ def main_from_args(args):
     try:
         result = args.func(args)
     except RuntimeError as e:
-        logging.error(six.text_type(e))
+        logging.error(str(e))
         return 1
     except IOError as e:
-        logging.error(six.text_type(e))
+        logging.error(str(e))
         return e.errno
 
     if result is None:

asdf/commands/tags.py

@@ -5,7 +5,6 @@
 Implementation of command for displaying available tags in asdf
 """
 
-from __future__ import absolute_import, division, unicode_literals, print_function
 
 import sys
 

asdf/commands/tests/__init__.py

@@ -1,4 +1,3 @@
 # Licensed under a 3-clause BSD style license - see LICENSE.rst
 # -*- coding: utf-8 -*-
 
-from __future__ import absolute_import, division, unicode_literals, print_function

asdf/commands/tests/setup_package.py

@@ -1,7 +1,6 @@
 # Licensed under a 3-clause BSD style license - see LICENSE.rst
 # -*- coding: utf-8 -*-
 
-from __future__ import absolute_import, division, unicode_literals, print_function
 
 
 def get_package_data():  # pragma: no cover

asdf/commands/tests/test_defragment.py

@@ -1,7 +1,6 @@
 # Licensed under a 3-clause BSD style license - see LICENSE.rst
 # -*- coding: utf-8 -*-
 
-from __future__ import absolute_import, division, unicode_literals, print_function
 
 import os
 import sys

asdf/commands/tests/test_diff.py

@@ -1,7 +1,6 @@
 # Licensed under a 3-clause BSD style license - see LICENSE.rst
 # -*- coding: utf-8 -*-
 
-from __future__ import absolute_import, division, unicode_literals, print_function
 
 import os
 import io

asdf/commands/tests/test_exploded.py

@@ -1,7 +1,6 @@
 # Licensed under a 3-clause BSD style license - see LICENSE.rst
 # -*- coding: utf-8 -*-
 
-from __future__ import absolute_import, division, unicode_literals, print_function
 
 import os
 

asdf/commands/tests/test_main.py

@@ -1,7 +1,6 @@
 # Licensed under a 3-clause BSD style license - see LICENSE.rst
 # -*- coding: utf-8 -*-
 
-from __future__ import absolute_import, division, unicode_literals, print_function
 
 import pytest
 

asdf/commands/tests/test_tags.py

@@ -1,7 +1,6 @@
 # Licensed under a 3-clause BSD style license - see LICENSE.rst
 # -*- coding: utf-8 -*-
 
-from __future__ import absolute_import, division, unicode_literals, print_function
 
 import io
 

asdf/commands/tests/test_to_yaml.py

@@ -1,7 +1,6 @@
 # Licensed under a 3-clause BSD style license - see LICENSE.rst
 # -*- coding: utf-8 -*-
 
-from __future__ import absolute_import, division, unicode_literals, print_function
 
 import os
 

asdf/commands/to_yaml.py

@@ -5,7 +5,6 @@
 Contains commands for dealing with exploded and imploded forms.
 """
 
-from __future__ import absolute_import, division, unicode_literals, print_function
 
 import os
 

asdf/compat/__init__.py

@@ -1,23 +1,2 @@
 # Licensed under a 3-clause BSD style license - see LICENSE.rst
 # -*- coding: utf-8 -*-
-
-from __future__ import absolute_import, division, unicode_literals, print_function
-
-import six
-
-if six.PY2:
-    from UserDict import UserDict
-    from UserList import UserList
-    from UserString import UserString
-elif six.PY3:
-    from .user_collections_py3.UserDict import UserDict
-    from .user_collections_py3.UserList import UserList
-    from .user_collections_py3.UserString import UserString
-
-if six.PY2:
-    from .functools_backport import lru_cache
-elif six.PY3:
-    try:
-        from functools import lru_cache
-    except ImportError:
-        from .functools_backport import lru_cache