Fix pandas-dev#16583 by adding an explicit mode argument to read_hdf

kwargs which are meant for the opening of the HDFStore should be filtered out
before passing the remaining kwargs to the `select` function to load the data.

pandas/io/pytables.py

@@ -282,21 +282,23 @@ def to_hdf(path_or_buf, key, value, mode=None, complevel=None, complib=None,
         f(path_or_buf)
 
 
-def read_hdf(path_or_buf, key=None, **kwargs):
+def read_hdf(path_or_buf, key=None, mode='r', **kwargs):
     """ read from the store, close it if we opened it
 
         Retrieve pandas object stored in file, optionally based on where
         criteria
 
         Parameters
         ----------
-        path_or_buf : path (string), buffer, or path object (pathlib.Path or
-            py._path.local.LocalPath) to read from
+        path_or_buf : path (string), buffer, open pd.HDFStore, or path object
+            (pathlib.Path or py._path.local.LocalPath) to read from
 
             .. versionadded:: 0.19.0 support for pathlib, py.path.
 
         key : group identifier in the store. Can be omitted if the HDF file
             contains a single pandas object.
+        mode : Mode to use when opening the file (ignored if path_or_buf is
+               a pd.HDFStore)
         where : list of Term (or convertable) objects, optional
         start : optional, integer (defaults to None), row number to start
             selection
@@ -313,10 +315,9 @@ def read_hdf(path_or_buf, key=None, **kwargs):
 
         """
 
-    if kwargs.get('mode', 'a') not in ['r', 'r+', 'a']:
+    if mode not in ['r', 'r+', 'a']:
         raise ValueError('mode {0} is not allowed while performing a read. '
-                         'Allowed modes are r, r+ and a.'
-                         .format(kwargs.get('mode')))
+                         'Allowed modes are r, r+ and a.'.format(mode))
     # grab the scope
     if 'where' in kwargs:
         kwargs['where'] = _ensure_term(kwargs['where'], scope_level=1)
@@ -343,7 +344,7 @@ def read_hdf(path_or_buf, key=None, **kwargs):
             raise compat.FileNotFoundError(
                 'File %s does not exist' % path_or_buf)
 
-        store = HDFStore(path_or_buf, **kwargs)
+        store = HDFStore(path_or_buf, mode=mode, **kwargs)
         # can't auto open/close if we are using an iterator
         # so delegate to the iterator
         auto_close = True