Add DataPackage.push method

I can load Data Packages via URLs from data.okfn.org (e.g. http://data.okfn.org/data/core/cpi/datapackage.json) or from within the working directory (e.g. “.”). I am having trouble, though, loading directly from GitHub (‘https://raw.githubusercontent.com/datasets/cpi/master/datapackage.json’) or anywhere else on the filesystem.

In my case, loading works well:

import datapackage
dp = datapackage.DataPackage('https://raw.githubusercontent.com/datasets/cpi/master/datapackage.json')

But when I try to push to e.g. an SQL database using:

push_datapackage(descriptor=dp.metadata,backend='sql',engine=engine)

I get the following error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/dan/open_knowledge/envs/tutorial/lib/python3.5/site-packages/datapackage/pushpull.py", line 53, in push_datapackage
    data = resource.iter()
  File "/Users/dan/open_knowledge/envs/tutorial/lib/python3.5/site-packages/datapackage/resource.py", line 297, in iter
    raise IOError('Resource\'s data couldn\'t be loaded.')
OSError: Resource's data couldn't be loaded.

For the above example of loading from https://raw.githubusercontent.com/datasets/cpi/master/datapackage.json, it seems to be trying to load directly from non-existent “data/cpi.csv” in the working directory and not “https://raw.githubusercontent.com/datasets/cpi/master/data/cpi.csv”

[vitorbaptista]

@rgrp Just to add to what @roll said, the problem here is that @danfowler was passing dp.metadata, which is just a dict. There’s no indication of where it came from. However, the DataPackage instance itself knows its base path and can calculate relative paths for the resources, which is why I think the push_datapackage and pull_datapackage needs to live inside the DataPackage class.

[vitorbaptista]

I think this is a weak point of the current design. The push and pull datapackage methods don’t fit with the rest of the code structure yet. Ideally, this should work:

import datapackage
dp = datapackage.DataPackage('https://raw.githubusercontent.com/datasets/cpi/master/datapackage.json')
dp.push(backend='sql', engine=engine)