Drop 2to3 build step; make all code compatible with all Pythons

Make all library code compatible with both Python 2 and Python 3. Helps
move to modern Python idioms. Can now write for Python 3 (with
workarounds for Python 2) instead of the other way around.

In the future, when it is eventually time to drop Python 2, the library
will be in a better position to remove workarounds

Added a very small comparability module compat.py where required. It
includes definitions for:

- text_type -- A type. str on Python 3. unicode on Python 2.
- string_types -- A tuple. Contains only str on Python 3. Contains str &
                  unicode on Python 2.

8 files changed, 39 insertions, 22 deletions

diff --git a/lib/_ipaddress.py b/lib/_ipaddress.py
index ee05a26..beb2fb3 100644
--- a/lib/_ipaddress.py
+++ b/lib/_ipaddress.py
@@ -25,6 +25,7 @@
 
 from psycopg2.extensions import (
     new_type, new_array_type, register_type, register_adapter, QuotedString)
+from psycopg2.compat import text_type
 
 # The module is imported on register_ipaddress
 ipaddress = None
@@ -76,13 +77,13 @@ def cast_interface(s, cur=None):
     if s is None:
         return None
     # Py2 version force the use of unicode. meh.
-    return ipaddress.ip_interface(unicode(s))
+    return ipaddress.ip_interface(text_type(s))
 
 
 def cast_network(s, cur=None):
     if s is None:
         return None
-    return ipaddress.ip_network(unicode(s))
+    return ipaddress.ip_network(text_type(s))
 
 
 def adapt_ipaddress(obj):
diff --git a/lib/_range.py b/lib/_range.py
index c1facc0..fd15a76 100644
--- a/lib/_range.py
+++ b/lib/_range.py
@@ -29,6 +29,7 @@ import re
 from psycopg2._psycopg import ProgrammingError, InterfaceError
 from psycopg2.extensions import ISQLQuote, adapt, register_adapter
 from psycopg2.extensions import new_type, new_array_type, register_type
+from psycopg2.compat import string_types
 
 
 class Range(object):
@@ -126,9 +127,13 @@ class Range(object):
 
         return True
 
-    def __nonzero__(self):
+    def __bool__(self):
         return self._bounds is not None
 
+    def __nonzero__(self):
+        # Python 2 compatibility
+        return type(self).__bool__(self)
+
     def __eq__(self, other):
         if not isinstance(other, Range):
             return False
@@ -296,7 +301,7 @@ class RangeCaster(object):
         # an implementation detail and is not documented. It is currently used
         # for the numeric ranges.
         self.adapter = None
-        if isinstance(pgrange, basestring):
+        if isinstance(pgrange, string_types):
             self.adapter = type(pgrange, (RangeAdapter,), {})
             self.adapter.name = pgrange
         else:
@@ -313,7 +318,7 @@ class RangeCaster(object):
 
         self.range = None
         try:
-            if isinstance(pyrange, basestring):
+            if isinstance(pyrange, string_types):
                 self.range = type(pyrange, (Range,), {})
             if issubclass(pyrange, Range) and pyrange is not Range:
                 self.range = pyrange
diff --git a/lib/compat.py b/lib/compat.py
new file mode 100644
index 0000000..cfd5a88
--- /dev/null
+++ b/lib/compat.py
@@ -0,0 +1,10 @@
+import sys
+
+if sys.version_info[0] == 2:
+    # Python 2
+    string_types = basestring,
+    text_type = unicode
+else:
+    # Python 3
+    string_types = str,
+    text_type = str
diff --git a/lib/errorcodes.py b/lib/errorcodes.py
index 24fcf25..b8742f5 100644
--- a/lib/errorcodes.py
+++ b/lib/errorcodes.py
@@ -40,7 +40,7 @@ def lookup(code, _cache={}):
 
     # Generate the lookup map at first usage.
     tmp = {}
-    for k, v in globals().iteritems():
+    for k, v in globals().items():
         if isinstance(v, str) and len(v) in (2, 5):
             tmp[v] = k
 
diff --git a/lib/extensions.py b/lib/extensions.py
index d15f76c..8644e41 100644
--- a/lib/extensions.py
+++ b/lib/extensions.py
@@ -163,7 +163,7 @@ def make_dsn(dsn=None, **kwargs):
         kwargs['dbname'] = kwargs.pop('database')
 
     # Drop the None arguments
-    kwargs = {k: v for (k, v) in kwargs.iteritems() if v is not None}
+    kwargs = {k: v for (k, v) in kwargs.items() if v is not None}
 
     if dsn is not None:
         tmp = parse_dsn(dsn)
@@ -171,7 +171,7 @@ def make_dsn(dsn=None, **kwargs):
         kwargs = tmp
 
     dsn = " ".join(["%s=%s" % (k, _param_escape(str(v)))
-        for (k, v) in kwargs.iteritems()])
+        for (k, v) in kwargs.items()])
 
     # verify that the returned dsn is valid
     parse_dsn(dsn)
@@ -216,7 +216,7 @@ del Range
 # When the encoding is set its name is cleaned up from - and _ and turned
 # uppercase, so an encoding not respecting these rules wouldn't be found in the
 # encodings keys and would raise an exception with the unicode typecaster
-for k, v in encodings.items():
+for k, v in list(encodings.items()):
     k = k.replace('_', '').replace('-', '').upper()
     encodings[k] = v
 
diff --git a/lib/extras.py b/lib/extras.py
index 64467a8..1b0b2b6 100644
--- a/lib/extras.py
+++ b/lib/extras.py
@@ -318,14 +318,14 @@ class NamedTupleCursor(_cursor):
         nt = self.Record
         if nt is None:
             nt = self.Record = self._make_nt()
-        return map(nt._make, ts)
+        return list(map(nt._make, ts))
 
     def fetchall(self):
         ts = super(NamedTupleCursor, self).fetchall()
         nt = self.Record
         if nt is None:
             nt = self.Record = self._make_nt()
-        return map(nt._make, ts)
+        return list(map(nt._make, ts))
 
     def __iter__(self):
         try:
@@ -566,7 +566,7 @@ class ReplicationCursor(_replicationCursor):
                     "cannot specify output plugin options for physical replication")
 
             command += " ("
-            for k, v in options.iteritems():
+            for k, v in options.items():
                 if not command.endswith('('):
                     command += ", "
                 command += "%s %s" % (quote_ident(k, self), _A(str(v)))
@@ -762,7 +762,7 @@ class HstoreAdapter(object):
 
         adapt = _ext.adapt
         rv = []
-        for k, v in self.wrapped.iteritems():
+        for k, v in self.wrapped.items():
             k = adapt(k)
             k.prepare(self.conn)
             k = k.getquoted()
@@ -784,9 +784,9 @@ class HstoreAdapter(object):
         if not self.wrapped:
             return b"''::hstore"
 
-        k = _ext.adapt(self.wrapped.keys())
+        k = _ext.adapt(list(self.wrapped.keys()))
         k.prepare(self.conn)
-        v = _ext.adapt(self.wrapped.values())
+        v = _ext.adapt(list(self.wrapped.values()))
         v.prepare(self.conn)
         return b"hstore(" + k.getquoted() + b", " + v.getquoted() + b")"
 
@@ -1112,7 +1112,7 @@ def _paginate(seq, page_size):
     it = iter(seq)
     while 1:
         try:
-            for i in xrange(page_size):
+            for i in range(page_size):
                 page.append(next(it))
             yield page
             page = []
diff --git a/lib/pool.py b/lib/pool.py
index a91c9cc..6c26f7d 100644
--- a/lib/pool.py
+++ b/lib/pool.py
@@ -209,8 +209,8 @@ class PersistentConnectionPool(AbstractConnectionPool):
 
         # we we'll need the thread module, to determine thread ids, so we
         # import it here and copy it in an instance variable
-        import thread as _thread  # work around for 2to3 bug - see ticket #348
-        self.__thread = _thread
+        import thread
+        self.__thread = thread
 
     def getconn(self):
         """Generate thread id and return a connection."""
diff --git a/lib/sql.py b/lib/sql.py
index 849b25f..7ba9295 100644
--- a/lib/sql.py
+++ b/lib/sql.py
@@ -27,6 +27,7 @@ import sys
 import string
 
 from psycopg2 import extensions as ext
+from psycopg2.compat import string_types
 
 
 _formatter = string.Formatter()
@@ -147,7 +148,7 @@ class Composed(Composable):
             "foo", "bar"
 
         """
-        if isinstance(joiner, basestring):
+        if isinstance(joiner, string_types):
             joiner = SQL(joiner)
         elif not isinstance(joiner, SQL):
             raise TypeError(
@@ -179,7 +180,7 @@ class SQL(Composable):
         select "foo", "bar" from "table"
     """
     def __init__(self, string):
-        if not isinstance(string, basestring):
+        if not isinstance(string, string_types):
             raise TypeError("SQL values must be strings")
         super(SQL, self).__init__(string)
 
@@ -308,7 +309,7 @@ class Identifier(Composable):
 
     """
     def __init__(self, string):
-        if not isinstance(string, basestring):
+        if not isinstance(string, string_types):
             raise TypeError("SQL identifiers must be strings")
 
         super(Identifier, self).__init__(string)
@@ -395,7 +396,7 @@ class Placeholder(Composable):
     """
 
     def __init__(self, name=None):
-        if isinstance(name, basestring):
+        if isinstance(name, string_types):
             if ')' in name:
                 raise ValueError("invalid name: %r" % name)