standardize ._tz directly

pandas-dev · jreback · Apr 11, 2018 · Mar 18, 2018 · Mar 19, 2018 · Mar 21, 2018
commit 67a29d54d0df33977a9cb4bd24b974e240073aa3
diff --git a/pandas/core/indexes/datetimes.py b/pandas/core/indexes/datetimes.py
@@ -649,6 +649,7 @@ def _simple_new(cls, values, name=None, freq=None, tz=None,
         result.name = name
         result.offset = freq
         result._tz = timezones.maybe_get_tz(tz)
+        result._tz = timezones.tz_standardize(result._tz)
         result._reset_identity()
         return result
 
@@ -678,10 +679,16 @@ def _values(self):
         else:
             return self.values
 
-    @cache_readonly
+    @property
     def tz(self):
         # GH 18595
 cdef class CachedProperty(object): 
     cdef readonly: 
         object func, name, __doc__ 
     def __init__(self, func): 
         self.func = func 
         self.name = func.__name__ 
         self.__doc__ = getattr(func, '__doc__', None) 
     def __get__(self, obj, typ): 
         if obj is None: 
             # accessed on the class, not the instance 
             return self 
         # Get the cache or set a default one if needed 
         cache = getattr(obj, '_cache', None) 
         if cache is None: 
             try: 
                 cache = obj._cache = {} 
             except (AttributeError): 
                 return self 
         if PyDict_Contains(cache, self.name): 
             # not necessary to Py_INCREF 
             val = <object> PyDict_GetItem(cache, self.name) 
         else: 
             val = self.func(obj) 
             PyDict_SetItem(cache, self.name, val) 
         return val 
     def __set__(self, obj, value): 
         raise AttributeError("Can't set attribute") 
 cache_readonly = CachedProperty 
 cdef class CachedProperty(object): 
  
     cdef readonly: 
         object func, name, __doc__ 
  
     def __init__(self, func): 
         self.func = func 
         self.name = func.__name__ 
         self.__doc__ = getattr(func, '__doc__', None) 
  
     def __get__(self, obj, typ): 
         if obj is None: 
             # accessed on the class, not the instance 
             return self 
  
         # Get the cache or set a default one if needed 
         cache = getattr(obj, '_cache', None) 
         if cache is None: 
             try: 
                 cache = obj._cache = {} 
             except (AttributeError): 
                 return self 
  
         if PyDict_Contains(cache, self.name): 
             # not necessary to Py_INCREF 
             val = <object> PyDict_GetItem(cache, self.name) 
         else: 
             val = self.func(obj) 
             PyDict_SetItem(cache, self.name, val) 
         return val 
  
     def __set__(self, obj, value): 
         raise AttributeError("Can't set attribute") 
  
  
 cache_readonly = CachedProperty 
-        return timezones.tz_standardize(self._tz)
+        return self._tz
+
+    @tz.setter
+    def tz(self, value):
+        # GH 3746: Prevent localizing or converting the index by setting tz
+        raise AttributeError("Cannot directly set timezone. Use tz_localize() "
+                             "or tz_convert() as appropriate")
 
     @property
     def tzinfo(self):
@@ -753,7 +760,7 @@ def _cached_range(cls, start=None, end=None, periods=None, offset=None,
 
             cachedRange = DatetimeIndex._simple_new(arr)
             cachedRange.offset = offset
-            cachedRange._tz = None
+            cachedRange = cachedRange.tz_localize(None)
             cachedRange.name = None
             drc[offset] = cachedRange
         else:
@@ -830,7 +837,7 @@ def __setstate__(self, state):
 
                 self.name = own_state[0]
                 self.offset = own_state[1]
-                self._tz = own_state[2]
+                self._tz = timezones.tz_standardize(own_state[2])
 
                 # provide numpy < 1.7 compat
                 if nd_state[2] == 'M8[us]':
@@ -1174,7 +1181,7 @@ def union(self, other):
         else:
             result = Index.union(this, other)
             if isinstance(result, DatetimeIndex):
-                result._tz = this.tz
+                result._tz = timezones.tz_standardize(this.tz)
                 if (result.freq is None and
                         (this.freq is not None or other.freq is not None)):
                     result.offset = to_offset(result.inferred_freq)
@@ -1222,7 +1229,7 @@ def union_many(self, others):
                 tz = this.tz
                 this = Index.union(this, other)
                 if isinstance(this, DatetimeIndex):
-                    this._tz = tz
+                    this._tz = timezones.tz_standardize(tz)
 
         if this.freq is None:
             this.offset = to_offset(this.inferred_freq)