diff --git a/cwr/grammar/factory/adapter.py b/cwr/grammar/factory/adapter.py
index 8fef85e..9870e66 100644
--- a/cwr/grammar/factory/adapter.py
+++ b/cwr/grammar/factory/adapter.py
@@ -25,7 +25,7 @@
 __status__ = 'Development'
 
 
-class FieldAdapter(object):
+class FieldAdapter(object, metaclass=ABCMeta):
     """
     Interface for adapting field rules creation to the parser factory
     requirements.
@@ -34,7 +34,6 @@ class FieldAdapter(object):
     and then generate a specific field rule
     from them.
     """
-    __metaclass__ = ABCMeta
 
     def __init__(self):
         pass
diff --git a/cwr/grammar/factory/decorator.py b/cwr/grammar/factory/decorator.py
index eefc4ff..d7b339c 100644
--- a/cwr/grammar/factory/decorator.py
+++ b/cwr/grammar/factory/decorator.py
@@ -21,9 +21,7 @@
 __status__ = 'Development'
 
 
-class RuleDecorator(object):
-    __metaclass__ = ABCMeta
-
+class RuleDecorator(object, metaclass=ABCMeta):
     def __init__(self):
         pass
 
diff --git a/cwr/grammar/factory/rule.py b/cwr/grammar/factory/rule.py
index ba6a7ea..8b65d30 100644
--- a/cwr/grammar/factory/rule.py
+++ b/cwr/grammar/factory/rule.py
@@ -15,9 +15,7 @@
 __status__ = 'Development'
 
 
-class RuleFactory(object):
-    __metaclass__ = ABCMeta
-
+class RuleFactory(object, metaclass=ABCMeta):
     def __init__(self):
         pass
 
diff --git a/cwr/interested_party.py b/cwr/interested_party.py
index a3a61d2..bea1e84 100644
--- a/cwr/interested_party.py
+++ b/cwr/interested_party.py
@@ -12,11 +12,10 @@
 __status__ = 'Development'
 
 
-class InterestedParty(object):
+class InterestedParty(object, metaclass=ABCMeta):
     """
     Represents a CWR interested party.
     """
-    __metaclass__ = ABCMeta
 
     def __init__(self,
                  ip_n='',
@@ -105,13 +104,12 @@ def tax_id(self, value):
         self._tax_id = value
 
 
-class InterestedPartyRecord(TransactionRecord):
+class InterestedPartyRecord(TransactionRecord, metaclass=ABCMeta):
     """
     Represents a CWR Interested Party Record.
 
     This is meant to be used for Publisher and Writer records.
     """
-    __metaclass__ = ABCMeta
 
     def __init__(self,
                  record_type='',
diff --git a/cwr/non_roman_alphabet.py b/cwr/non_roman_alphabet.py
index 1a333fa..3953fd3 100644
--- a/cwr/non_roman_alphabet.py
+++ b/cwr/non_roman_alphabet.py
@@ -12,13 +12,12 @@
 __status__ = 'Development'
 
 
-class NonRomanAlphabetRecord(TransactionRecord):
+class NonRomanAlphabetRecord(TransactionRecord, metaclass=ABCMeta):
     """
     Represents a CWR Non-Roman Alphabet record.
 
     These are the records to represent alternate names out of the ASCII table.
     """
-    __metaclass__ = ABCMeta
 
     def __init__(self,
                  record_type='',
diff --git a/cwr/parser/decoder/common.py b/cwr/parser/decoder/common.py
index 5657bb2..2b04f34 100644
--- a/cwr/parser/decoder/common.py
+++ b/cwr/parser/decoder/common.py
@@ -28,12 +28,11 @@
 __status__ = 'Development'
 
 
-class Decoder(object):
+class Decoder(object, metaclass=ABCMeta):
     """
     Interface for implementing decoder parsers. These parser receive a data
     structure and return an instance of a class from the domain model.
     """
-    __metaclass__ = ABCMeta
 
     def __init__(self):
         pass
diff --git a/cwr/parser/decoder/file.py b/cwr/parser/decoder/file.py
index f2903e7..daa2535 100644
--- a/cwr/parser/decoder/file.py
+++ b/cwr/parser/decoder/file.py
@@ -170,7 +170,7 @@ def default_grammar_factory():
 
     field_values = CWRTables()
 
-    for entry in data.values():
+    for entry in list(data.values()):
         if 'source' in entry:
             values_id = entry['source']
             entry['values'] = field_values.get_data(values_id)
@@ -206,7 +206,7 @@ def default_filename_grammar_factory():
     data = config.load_field_config('filename')
     field_values = CWRTables()
 
-    for entry in data.values():
+    for entry in list(data.values()):
         if 'source' in entry:
             values_id = entry['source']
             entry['values'] = field_values.get_data(values_id)
diff --git a/cwr/parser/encoder/common.py b/cwr/parser/encoder/common.py
index 1cfbe82..0c789e5 100644
--- a/cwr/parser/encoder/common.py
+++ b/cwr/parser/encoder/common.py
@@ -20,12 +20,11 @@
 __status__ = 'Development'
 
 
-class Encoder(object):
+class Encoder(object, metaclass=ABCMeta):
     """
     Interface for implementing encoder parsers. These parser receive a class
     from the domain model and return a data structure.
     """
-    __metaclass__ = ABCMeta
 
     def __init__(self):
         pass
diff --git a/cwr/record.py b/cwr/record.py
index 4d0dcbb..418d175 100644
--- a/cwr/record.py
+++ b/cwr/record.py
@@ -66,7 +66,7 @@ def record_type(self, value):
         self._record_type = value
 
 
-class TransactionRecord(Record):
+class TransactionRecord(Record, metaclass=ABCMeta):
     """
     Represents a CWR Transaction Record.
 
@@ -89,7 +89,6 @@ class TransactionRecord(Record):
     the one of the previous paragraph), and that it is the 3th (starting with
     1) detail on the file.
     """
-    __metaclass__ = ABCMeta
 
     def __init__(self,
                  record_type='',
diff --git a/cwr/work.py b/cwr/work.py
index 377a88f..e9b89ea 100644
--- a/cwr/work.py
+++ b/cwr/work.py
@@ -51,7 +51,7 @@
 __status__ = 'Development'
 
 
-class BaseWorkRecord(TransactionRecord):
+class BaseWorkRecord(TransactionRecord, metaclass=ABCMeta):
     """
     Abstract class representing a Work's basic information.
 
@@ -62,7 +62,6 @@ class BaseWorkRecord(TransactionRecord):
     This is meant to store the data which identifies a work in a generic way,
     which are the title, the language and the ISWC.
     """
-    __metaclass__ = ABCMeta
 
     def __init__(self,
                  record_type='',
diff --git a/tests/grammar/factory/test_default_rule_factory_stress.py b/tests/grammar/factory/test_default_rule_factory_stress.py
index 5949475..730844b 100644
--- a/tests/grammar/factory/test_default_rule_factory_stress.py
+++ b/tests/grammar/factory/test_default_rule_factory_stress.py
@@ -23,7 +23,7 @@ def test_10(self):
 
         record = ''
         if sys.version_info[0] == 2:
-            for x in xrange(35):
+            for x in range(35):
                 if len(record) == 0:
                     record = _agreement_full()
                 elif len(record) > 0:
diff --git a/tests/grammar/factory/test_default_rule_factory_times.py b/tests/grammar/factory/test_default_rule_factory_times.py
index 443702e..c07bfe1 100644
--- a/tests/grammar/factory/test_default_rule_factory_times.py
+++ b/tests/grammar/factory/test_default_rule_factory_times.py
@@ -21,7 +21,7 @@ def setUp(self):
     def test_10000(self):
         start = time.clock()
         if sys.version_info[0] == 2:
-            for x in xrange(10000):
+            for x in range(10000):
                 self._factory.get_rule('transmission')
         else:
             for x in range(10000):
diff --git a/tests/grammar/factory/test_field_factory_times.py b/tests/grammar/factory/test_field_factory_times.py
index 2ef6235..9b526bf 100644
--- a/tests/grammar/factory/test_field_factory_times.py
+++ b/tests/grammar/factory/test_field_factory_times.py
@@ -32,7 +32,7 @@ def setUp(self):
     def test_10000(self):
         start = time.clock()
         if sys.version_info[0] == 2:
-            for x in xrange(10000):
+            for x in range(10000):
                 self._factory.get_rule('test_field')
         else:
             for x in range(10000):
diff --git a/tests/visual/file_contents.py b/tests/visual/file_contents.py
index 48525db..5160b92 100644
--- a/tests/visual/file_contents.py
+++ b/tests/visual/file_contents.py
@@ -21,11 +21,11 @@
 
 if __name__ == '__main__':
     print('File contents parsing test')
-    path = raw_input(
+    path = input(
         'Please enter the full path to a CWR file (e.g. c:/documents/file.cwr): ')
-    output = raw_input(
+    output = input(
         'Please enter the full path to the file where the results will be stored: ')
-    log = raw_input(
+    log = input(
         'Please enter the full path to the file where parsing log will be saved: ')
     print('\n')
     print('Reading file %s' % path)
diff --git a/tests/visual/file_json.py b/tests/visual/file_json.py
index 584731c..f9f44c8 100644
--- a/tests/visual/file_json.py
+++ b/tests/visual/file_json.py
@@ -20,9 +20,9 @@
 
 if __name__ == '__main__':
     print('File to JSON test')
-    path = raw_input(
+    path = input(
         'Please enter the full path to a CWR file (e.g. c:/documents/file.cwr): ')
-    output = raw_input(
+    output = input(
         'Please enter the full path to the file where the results will be stored: ')
     print('\n')
     print('Reading file %s' % path)