title: How to read multiple parquet files (with same schema) from multiple directories with dask/fastparquet
body: <p>I need to use dask to load multiple parquet files with identical schema into a single dataframe.  This works when they are all in the same directory, but not when they're in separate directories.</p>
  
  <p>For example:</p>
  
  <pre><code>import fastparquet
  pfile = fastparquet.ParquetFile(['data/data1.parq', 'data/data2.parq'])
  </code></pre>
  
  <p>works just fine, but if I copy <code>data2.parq</code> to a different directory, the following does not work:</p>
  
  <pre><code>pfile = fastparquet.ParquetFile(['data/data1.parq', 'data2/data2.parq'])
  </code></pre>
  
  <p>The traceback I get is the following:</p>
  
  <pre><code>---------------------------------------------------------------------------
  ValueError                                Traceback (most recent call last)
  &lt;ipython-input-11-b3d381f14edc&gt; in &lt;module&gt;()
  ----&gt; 1 pfile = fastparquet.ParquetFile(['data/data1.parq', 'data2/data2.parq'])
  
  ~/anaconda/envs/hv/lib/python3.6/site-packages/fastparquet/api.py in __init__(self, fn, verify, open_with, sep)
       82         if isinstance(fn, (tuple, list)):
       83             basepath, fmd = metadata_from_many(fn, verify_schema=verify,
  ---&gt; 84                                                open_with=open_with)
       85             self.fn = sep.join([basepath, '_metadata'])  # effective file
       86             self.fmd = fmd
  
  ~/anaconda/envs/hv/lib/python3.6/site-packages/fastparquet/util.py in metadata_from_many(file_list, verify_schema, open_with)
      164     else:
      165         raise ValueError("Merge requires all PaquetFile instances or none")
  --&gt; 166     basepath, file_list = analyse_paths(file_list, sep)
      167 
      168     if verify_schema:
  
  ~/anaconda/envs/hv/lib/python3.6/site-packages/fastparquet/util.py in analyse_paths(file_list, sep)
      221     if len({tuple([p.split('=')[0] for p in parts[l:-1]])
      222             for parts in path_parts_list}) &gt; 1:
  --&gt; 223         raise ValueError('Partitioning directories do not agree')
      224     for path_parts in path_parts_list:
      225         for path_part in path_parts[l:-1]:
  
  ValueError: Partitioning directories do not agree
  </code></pre>
  
  <p>I get the same error when using <code>dask.dataframe.read_parquet</code>, which I assume uses the same <code>ParquetFile</code> object.</p>
  
  <p>How can I load multiple files from different directories?  Putting all the files I need to load into the same directory is not an option.</p>