On 07/22/2013 10:17 PM, jreback wrote:
>
> In pandas/core/frame.py:
>
> >                  have_raw_arrays = True
> >                  raw_lengths.append(len(v))
> > +            else:
> > +                # Item v silently ignored (to conserve
> > +                # the original behaviour - see also
>
> didn't realize that this happens.....can you see if you can gett a 
> case to fail (so we can see why?)
>

The item is silently ignored, that's for certain.
Otherwise, I put my wish to see this raise an exception on hold (I have 
updated my pull request). An item skipped silently will be
considered a scalar and repeated as deemed necessary to match the number 
of elements
in sequences.

Consider the following example:
```python
import pandas
dataf = pandas.DataFrame.from_items([('A', range(5)), ('B', None)])
```
The second `tuple` in the `list` will be skipped, and `None` will be 
repeated 5 times in the resulting `DataFrame`.
The second column in the `DataFrame` is otherwise behaving like a 
regular column:
```python
dataf['B'][2] = 3
```
Now I do not have sufficient knowledge / overview of places where 
`extract_index()` is used to assess whether it is clean to just skip an 
item or the inevitable special treatment resulting from this is creating 
more quirks in rest of the code than it is worth.


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