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Dict/dict keys in DataFrame.getitem

See original GitHub issue

Code Sample, a copy-pastable example if possible

In [2]: pd.Series(index=range(10))[{1:2,3:4}]
Out[2]: 
1   NaN
3   NaN
dtype: float64

In [3]: pd.Series(index=range(10))[{1:2,3:4}.keys()]
Out[3]: 
1   NaN
3   NaN
dtype: float64

In [4]: pd.DataFrame(index=range(10), columns=range(10))[{1:2,3:4}]
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-4-5b29d5d42cf2> in <module>()
----> 1 pd.DataFrame(index=range(10), columns=range(10))[{1:2,3:4}]

~/nobackup/repo/pandas/pandas/core/frame.py in __getitem__(self, key)
   2683             return self._getitem_multilevel(key)
   2684         else:
-> 2685             return self._getitem_column(key)
   2686 
   2687     def _getitem_column(self, key):

~/nobackup/repo/pandas/pandas/core/frame.py in _getitem_column(self, key)
   2690         # get column
   2691         if self.columns.is_unique:
-> 2692             return self._get_item_cache(key)
   2693 
   2694         # duplicate columns & possible reduce dimensionality

~/nobackup/repo/pandas/pandas/core/generic.py in _get_item_cache(self, item)
   2482         """Return the cached item, item represents a label indexer."""
   2483         cache = self._item_cache
-> 2484         res = cache.get(item)
   2485         if res is None:
   2486             values = self._data.get(item)

TypeError: unhashable type: 'dict'

In [5]: pd.DataFrame(index=range(10), columns=range(10))[{1:2,3:4}.keys()]
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-5-030f516d9637> in <module>()
----> 1 pd.DataFrame(index=range(10), columns=range(10))[{1:2,3:4}.keys()]

~/nobackup/repo/pandas/pandas/core/frame.py in __getitem__(self, key)
   2683             return self._getitem_multilevel(key)
   2684         else:
-> 2685             return self._getitem_column(key)
   2686 
   2687     def _getitem_column(self, key):

~/nobackup/repo/pandas/pandas/core/frame.py in _getitem_column(self, key)
   2690         # get column
   2691         if self.columns.is_unique:
-> 2692             return self._get_item_cache(key)
   2693 
   2694         # duplicate columns & possible reduce dimensionality

~/nobackup/repo/pandas/pandas/core/generic.py in _get_item_cache(self, item)
   2482         """Return the cached item, item represents a label indexer."""
   2483         cache = self._item_cache
-> 2484         res = cache.get(item)
   2485         if res is None:
   2486             values = self._data.get(item)

TypeError: unhashable type: 'dict_keys'

Problem description

I know that DataFrame.__getitem__ is a mess ( #9595 ), but I don’t see why dicts and dict keys shouldn’t be just considered list-likes as it happens with Series.

Expected Output

In [6]: pd.DataFrame(index=range(10), columns=range(10))[list({1:2,3:4})]
Out[6]: 
     1    3
0  NaN  NaN
1  NaN  NaN
2  NaN  NaN
3  NaN  NaN
4  NaN  NaN
5  NaN  NaN
6  NaN  NaN
7  NaN  NaN
8  NaN  NaN
9  NaN  NaN

Output of `pd.show_versions()`

INSTALLED VERSIONS

commit: None python: 3.5.3.final.0 python-bits: 64 OS: Linux OS-release: 4.9.0-6-amd64 machine: x86_64 processor: byteorder: little LC_ALL: None LANG: it_IT.UTF-8 LOCALE: it_IT.UTF-8

pandas: 0.24.0.dev0+25.gcd0447102 pytest: 3.5.0 pip: 9.0.1 setuptools: 39.2.0 Cython: 0.25.2 numpy: 1.14.3 scipy: 0.19.0 pyarrow: None xarray: None IPython: 6.2.1 sphinx: 1.5.6 patsy: 0.5.0 dateutil: 2.7.3 pytz: 2018.4 blosc: None bottleneck: 1.2.0dev tables: 3.3.0 numexpr: 2.6.1 feather: 0.3.1 matplotlib: 2.2.2.post1153+gff6786446 openpyxl: 2.3.0 xlrd: 1.0.0 xlwt: 1.3.0 xlsxwriter: 0.9.6 lxml: 4.1.1 bs4: 4.5.3 html5lib: 0.999999999 sqlalchemy: 1.0.15 pymysql: None psycopg2: None jinja2: 2.10 s3fs: None fastparquet: None pandas_gbq: None pandas_datareader: 0.2.1