Make int_convert stateless (#119)

* Add test for stateful int_convert

* Make int_convert stateless

If there is a "d"-type parameter in parser format,
converter is created with unspecified base.
After parsing first number, the base of this number
is stored in the class
and the same base is assumed
for all subsequent numbers parsed by this Parser instance.

parse.py

@@ -536,24 +536,25 @@ def __call__(self, string, match):
             sign = 1
             number_start = 0
 
+        base = self.base
         # If base wasn't specified, detect it automatically
-        if self.base is None:
+        if base is None:
 
             # Assume decimal number, unless different base is detected
-            self.base = 10
+            base = 10
 
             # For number formats starting with 0b, 0o, 0x, use corresponding base ...
             if string[number_start] == '0' and len(string) - number_start > 2:
                 if string[number_start + 1] in 'bB':
-                    self.base = 2
+                    base = 2
                 elif string[number_start + 1] in 'oO':
-                    self.base = 8
+                    base = 8
                 elif string[number_start + 1] in 'xX':
-                    self.base = 16
+                    base = 16
 
-        chars = int_convert.CHARS[: self.base]
+        chars = int_convert.CHARS[: base]
         string = re.sub('[^%s]' % chars, '', string.lower())
-        return sign * int(string, self.base)
+        return sign * int(string, base)
 
 
 class convert_first:

test_parse.py

@@ -1059,6 +1059,10 @@ def test_width_empty_input(self):
         res = parse.parse('{:2d}', '')
         self.assertIsNone(res)
 
+    def test_int_convert_stateless_base(self):
+        parser = parse.Parser("{:d}")
+        self.assertEqual(parser.parse("1234")[0], 1234)
+        self.assertEqual(parser.parse("0b1011")[0], 0b1011)
 
 if __name__ == '__main__':
     unittest.main()