QST: Indexing over empty DataFrame
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#### Question about pandas

Is it correct behavior when indexing over empty DataFrame?
```python
import pandas
df = pandas.DataFrame()
df
Empty DataFrame
Columns: []
Index: []

df.iloc[:, 3:9] # this doesn't throw an exception
Empty DataFrame
Columns: []
Index: []

df.iloc[:, 3] # this throws the exception
IndexError: single positional indexer is out-of-bounds

df[3:9] # this doesn't throw an exception
Empty DataFrame
Columns: []
Index: []

df[3] # this throws the exception
KeyError: 3
```
