thrift: treat required fields as positional arguments while generatin…

…g init, closes Thriftpy#119

thriftpy2/thrift.py

@@ -68,9 +68,23 @@ def __init__(self):
             pass
         return __init__
 
-    varnames, defaults = zip(*spec)
+    args = []
+    kwargs = []
+    varnames = []
+    defaults = []
+    for spec_element, t_spec in zip(spec, cls.thrift_spec.values()):
+        varnames.append(spec_element[0])
+        if t_spec[2]:
+            args.append(spec_element[0])
+        else:
+            kwargs.append(spec_element)
+            defaults.append(spec_element[1])
+
+    defaults = tuple(defaults) if defaults else None
+
+    args.extend(map('{0[0]}={0[1]!r}'.format, kwargs))
+    args = ', '.join(args)
 
-    args = ', '.join(map('{0[0]}={0[1]!r}'.format, spec))
     init = "def __init__(self, {}):\n".format(args)
     init += "\n".join(map('    self.{0} = {0}'.format, varnames))