Issue #6081: Add str.format_map. str.format_map(mapping) is similar to str.format(**mapping), except mapping does not get converted to a dict.

1 files changed, 78 insertions, 0 deletions

diff --git a/Lib/test/test_unicode.py b/Lib/test/test_unicode.py
index 7927834..cc891bd 100644
--- a/Lib/test/test_unicode.py
+++ b/Lib/test/test_unicode.py
@@ -695,6 +695,84 @@ class UnicodeTest(string_tests.CommonTest,
         self.assertRaises(ValueError, format, '', '#')
         self.assertRaises(ValueError, format, '', '#20')
 
+    def test_format_map(self):
+        self.assertEqual(''.format_map({}), '')
+        self.assertEqual('a'.format_map({}), 'a')
+        self.assertEqual('ab'.format_map({}), 'ab')
+        self.assertEqual('a{{'.format_map({}), 'a{')
+        self.assertEqual('a}}'.format_map({}), 'a}')
+        self.assertEqual('{{b'.format_map({}), '{b')
+        self.assertEqual('}}b'.format_map({}), '}b')
+        self.assertEqual('a{{b'.format_map({}), 'a{b')
+
+        # using mappings
+        class Mapping(dict):
+            def __missing__(self, key):
+                return key
+        self.assertEqual('{hello}'.format_map(Mapping()), 'hello')
+        self.assertEqual('{a} {world}'.format_map(Mapping(a='hello')), 'hello world')
+
+        class InternalMapping:
+            def __init__(self):
+                self.mapping = {'a': 'hello'}
+            def __getitem__(self, key):
+                return self.mapping[key]
+        self.assertEqual('{a}'.format_map(InternalMapping()), 'hello')
+
+
+        # classes we'll use for testing
+        class C:
+            def __init__(self, x=100):
+                self._x = x
+            def __format__(self, spec):
+                return spec
+
+        class D:
+            def __init__(self, x):
+                self.x = x
+            def __format__(self, spec):
+                return str(self.x)
+
+        # class with __str__, but no __format__
+        class E:
+            def __init__(self, x):
+                self.x = x
+            def __str__(self):
+                return 'E(' + self.x + ')'
+
+        # class with __repr__, but no __format__ or __str__
+        class F:
+            def __init__(self, x):
+                self.x = x
+            def __repr__(self):
+                return 'F(' + self.x + ')'
+
+        # class with __format__ that forwards to string, for some format_spec's
+        class G:
+            def __init__(self, x):
+                self.x = x
+            def __str__(self):
+                return "string is " + self.x
+            def __format__(self, format_spec):
+                if format_spec == 'd':
+                    return 'G(' + self.x + ')'
+                return object.__format__(self, format_spec)
+
+        # class that returns a bad type from __format__
+        class H:
+            def __format__(self, format_spec):
+                return 1.0
+
+        self.assertEqual('{foo._x}'.format_map({'foo': C(20)}), '20')
+
+        # test various errors
+        self.assertRaises(TypeError, '{'.format_map)
+        self.assertRaises(TypeError, '}'.format_map)
+        self.assertRaises(TypeError, 'a{'.format_map)
+        self.assertRaises(TypeError, 'a}'.format_map)
+        self.assertRaises(TypeError, '{a'.format_map)
+        self.assertRaises(TypeError, '}a'.format_map)
+
     def test_format_auto_numbering(self):
         class C:
             def __init__(self, x=100):