How to specify metadata for dask.dataframe
<p>Providing metadata became very important in  dask 0.11. The API provides some good examples, how to achieve that, but when it comes to picking the right dtypes for my dataframe, I still feel unsure.</p>

<ul>
<li>Could I do something like <code>meta={'x': int 'y': float,
'z': float}</code> instead of <code>meta={'x': 'i8', 'y': 'f8', 'z': 'f8'}</code>?</li>
<li>Could somebody hint me to a list of possible values like 'i8'?  What
dtypes exist? </li>
<li>How    can I specify a column, that contains arbitrary objects? How can I    specify a column, that contains only instances of one class?</li>
</ul>

<p>Both Dask.dataframe and Pandas use NumPy dtypes.  In particular, anything within that you can pass to <a href="http://docs.scipy.org/doc/numpy/reference/generated/numpy.dtype.html" rel="nofollow">np.dtype</a>.  This includes the following:</p>

<ol>
<li>NumPy dtype objects, like <code>np.float64</code></li>
<li>Python type objects, like <code>float</code></li>
<li>NumPy dtype strings, like <code>'f8'</code></li>
</ol>

<p>Here is a more extensive list taken from the NumPy docs: <a href="http://docs.scipy.org/doc/numpy/reference/arrays.dtypes.html#specifying-and-constructing-data-types" rel="nofollow">http://docs.scipy.org/doc/numpy/reference/arrays.dtypes.html#specifying-and-constructing-data-types</a></p>

python pandas dask