BUG: Improve _as_str() to handle DataFrame and other inputs

Fixes #44

Author: kernc

backtesting/_util.py

@@ -15,11 +15,13 @@ def try_(lazy_func, default=None, exception=Exception):
 def _as_str(value):
     if isinstance(value, (Number, str)):
         return str(value)
+    if isinstance(value, pd.DataFrame):
+        return 'df'
     name = str(getattr(value, 'name', '') or '')
+    if name in ('Open', 'High', 'Low', 'Close', 'Volume'):
+        return name[:1]
     if callable(value):
-        name = value.__name__.replace('<lambda>', '')
-    if name in ('Open', 'High', 'Low', 'Close'):
-        name = name[:1]
+        name = value.__name__.replace('<lambda>', 'λ')
     if len(name) > 10:
         name = name[:9] + '…'
     return name
@@ -93,13 +95,13 @@ def __init__(self, df):
         self.__arrays['__index'] = df.index.copy()
 
     def __getitem__(self, item):
-        return getattr(self, item)
+        return self.__get_array(item)
 
     def __getattr__(self, item):
         try:
             return self.__get_array(item)
         except KeyError:
-            raise KeyError("Column '{}' not in data".format(item)) from None
+            raise AttributeError("Column '{}' not in data".format(item)) from None
 
     def _set_length(self, i):
         self.__i = i

backtesting/backtesting.py

@@ -115,7 +115,7 @@ def init():
         """
         if name is None:
             params = ','.join(filter(None, map(_as_str, chain(args, kwargs.values()))))
-            func_name = func.__name__.replace('<lambda>', 'λ')
+            func_name = _as_str(func)
             name = ('{}({})' if params else '{}').format(func_name, params)
         else:
             name = name.format(*map(_as_str, args),

backtesting/test/_test.py

@@ -130,12 +130,8 @@ def init(self):
                 assert resampled in self._indicators, "Strategy.I not called"
                 assert resampled_ind in self._indicators, "Strategy.I not called"
 
-                try:
-                    self.data.X
-                except KeyError:
-                    pass
-                else:
-                    assert False
+                assert 1 == try_(lambda: self.data.X, 1, AttributeError)
+                assert 1 == try_(lambda: self.data['X'], 1, KeyError)
 
                 assert self.data.pip == .01
 
@@ -588,8 +584,10 @@ class Class:
         self.assertEqual(_as_str(_Indicator([1, 2], name='x')), 'x')
         self.assertEqual(_as_str(func), 'func')
         self.assertEqual(_as_str(Class), 'Class')
-        self.assertEqual(_as_str(lambda x: x), '')
-        for s in ('Open', 'High', 'Low', 'Close'):
+        self.assertEqual(_as_str(pd.Series([1, 2], name='x')), 'x')
+        self.assertEqual(_as_str(pd.DataFrame()), 'df')
+        self.assertEqual(_as_str(lambda x: x), 'λ')
+        for s in ('Open', 'High', 'Low', 'Close', 'Volume'):
             self.assertEqual(_as_str(_Array([1], name=s)), s[0])