add pretty print for models (#42)

HISTORY.rst

@@ -6,6 +6,7 @@ History
 v0.2.0 (TBC)
 ............
 * allow annotation only fields to support mypy
+* add pretty ``to_string(pretty=True)`` method for models
 
 v0.1.0 (2017-06-03)
 ...................

pydantic/main.py

@@ -201,6 +201,24 @@ class BaseModel(metaclass=MetaModel):
     def __repr__(self):
         return f'<{self}>'
 
+    @classmethod
+    def _truncate(cls, v):
+        max_len = 80
+        if isinstance(v, str) and len(v) > (max_len - 2):
+            # 45 so quote + string + ... + quote has length 50
+            return repr(v[:(max_len - 5)] + '...')
+        v = repr(v)
+        if len(v) > max_len:
+            v = v[:max_len - 3] + '...'
+        return v
+
+    def to_string(self, pretty=False):
+        divider = '\n  ' if pretty else ' '
+        return '{}{}{}'.format(
+            self.__class__.__name__,
+            divider,
+            divider.join('{}={}'.format(k, self._truncate(v)) for k, v in self.__values__.items()),
+        )
+
     def __str__(self):
-        return '{} {}'.format(self.__class__.__name__, ' '.join('{}={!r}'.format(k, v)
-                                                                for k, v in self.__values__.items()))
+        return self.to_string()

tests/test_main.py

@@ -51,6 +51,26 @@ def test_ultra_simple_repr():
     assert dict(m) == {'a': 10.2, 'b': 10}
 
 
+def test_str_truncate():
+    class Model(BaseModel):
+        s1: str
+        s2: str
+        b1: bytes
+        b2: bytes
+    m = Model(s1='132', s2='x' * 100, b1='123', b2='x' * 100)
+    print(repr(m.to_string()))
+    assert m.to_string() == ("Model s1='132' "
+                             "s2='xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx...' "
+                             "b1=b'123' "
+                             "b2=b'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx...")
+    assert """\
+Model
+  s1='132'
+  s2='xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx...'
+  b1=b'123'
+  b2=b'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx...""" == m.to_string(pretty=True)
+
+
 def test_comparing():
     m = UltraSimpleModel(a=10.2, b='100')
     assert m == {'a': 10.2, 'b': 100}