STY Replace appending of Series with dict comprehension.

Author: twiecki

pyfolio/timeseries.py

@@ -739,17 +739,11 @@ def perf_stats(returns, factor_returns=None):
 
     """
 
-    stats = pd.Series()
-
-    for stat_func in SIMPLE_STAT_FUNCS:
-        stats[stat_func.__name__] = stat_func(returns)
-
-    if factor_returns is not None:
-        for stat_func in FACTOR_STAT_FUNCS:
-            stats[stat_func.__name__] = stat_func(returns,
-                                                  factor_returns)
-
-    return stats
+    return pd.Series(OrderedDict(
+        (stats_func.__name__, stats_func(returns)
+         for stats_func in SIMPLE_STATS_FUNCS +
+         (FACTOR_STAT_FUNCS if factor_returns else [])
+     ))
 
 
 def get_max_drawdown_underwater(underwater):