PERF: speed up .ix by moving deprecation string out of __init__ (pandas-dev#24747)

Author: qwhelan

pandas/core/indexing.py

@@ -1405,17 +1405,16 @@ class _IXIndexer(_NDFrameIndexer):
     See more at :ref:`Advanced Indexing <advanced>`.
     """
 
-    def __init__(self, name, obj):
-
-        _ix_deprecation_warning = textwrap.dedent("""
-            .ix is deprecated. Please use
-            .loc for label based indexing or
-            .iloc for positional indexing
+    _ix_deprecation_warning = textwrap.dedent("""
+        .ix is deprecated. Please use
+        .loc for label based indexing or
+        .iloc for positional indexing
 
-            See the documentation here:
-            http://pandas.pydata.org/pandas-docs/stable/indexing.html#ix-indexer-is-deprecated""")  # noqa
+        See the documentation here:
+        http://pandas.pydata.org/pandas-docs/stable/indexing.html#ix-indexer-is-deprecated""")  # noqa
 
-        warnings.warn(_ix_deprecation_warning,
+    def __init__(self, name, obj):
+        warnings.warn(self._ix_deprecation_warning,
                       DeprecationWarning, stacklevel=2)
         super(_IXIndexer, self).__init__(name, obj)