ENH: add to_series() method to Index and subclasses GH3275

Author: y-p

RELEASE.rst

@@ -49,6 +49,8 @@ pandas 0.11.0
   - Added support for expression evaluation using the ``numexpr`` library
   - Added ``convert=boolean`` to ``take`` routines to translate negative
     indices to positive, defaults to True
+  - Added to_series() method to indices, to facilitate the creation of indexeres
+    (GH3275_)
 
 **Improvements to existing features**
 
@@ -277,6 +279,7 @@ pandas 0.11.0
 .. _GH1893: https://github.com/pydata/pandas/issues/1893
 .. _GH1978: https://github.com/pydata/pandas/issues/1978
 .. _GH2758: https://github.com/pydata/pandas/issues/2758
+.. _GH3275: https://github.com/pydata/pandas/issues/3275
 .. _GH2121: https://github.com/pydata/pandas/issues/2121
 .. _GH3247: https://github.com/pydata/pandas/issues/3247
 .. _GH2809: https://github.com/pydata/pandas/issues/2809

doc/source/v0.11.0.txt

@@ -226,6 +226,9 @@ Astype conversion on ``datetime64[ns]`` to ``object``, implicity converts ``NaT`
 API changes
 ~~~~~~~~~~~
 
+  - Added to_series() method to indicies, to facilitate the creation of indexers
+    (GH3275_)
+
   - In ``HDFStore``, added the method ``select_column`` to select a single column from a table as a Series.
 
   - In ``HDFStore``, deprecated the ``unique`` method, can be replicated by ``select_column(key,column).unique()``
@@ -343,6 +346,7 @@ on GitHub for a complete list.
 .. _GH2807: https://github.com/pydata/pandas/issues/2807
 .. _GH2918: https://github.com/pydata/pandas/issues/2918
 .. _GH2758: https://github.com/pydata/pandas/issues/2758
+.. _GH3275: https://github.com/pydata/pandas/issues/3275
 .. _GH2979: https://github.com/pydata/pandas/issues/2979
 .. _GH3011: https://github.com/pydata/pandas/issues/3011
 .. _GH3076: https://github.com/pydata/pandas/issues/3076

pandas/core/index.py

@@ -188,6 +188,14 @@ def __repr__(self):
         """
         return str(self)
 
+    def to_series(self):
+        """
+        return a series with both index and values equal to the index keys
+        useful with map for returning an indexer based on an index
+        """
+        import pandas as pd
+        return pd.Series(self.values,index=self,name=self.name)
+
     def astype(self, dtype):
         return Index(self.values.astype(dtype), name=self.name,
                      dtype=dtype)