Pydap¶
Pydap is a pure Python library implementing the Data Access Protocol, also known as DODS or OPeNDAP. You can use Pydap as a client to access hundreds of scientific datasets in a transparent and efficient way through the internet; or as a server to easily distribute your data from a variety of formats.
Quickstart¶
You can install the latest version (3.2) using pip. After installing pip you can install Pydap with this command:
$ pip install Pydap
This will install Pydap together with all the required dependencies. You can now open any remotely served dataset, and Pydap will download the accessed data on-the-fly as needed:
>>> from pydap.client import open_url
>>> dataset = open_url('http://test.opendap.org/dap/data/nc/coads_climatology.nc')
>>> var = dataset['SST']
>>> var.shape
(12, 90, 180)
>>> var.dtype
dtype('>f4')
>>> data = var[0,10:14,10:14] # this will download data from the server
>>> data
<GridType with array 'SST' and maps 'TIME', 'COADSY', 'COADSX'>
>>> print(data.data)
[array([[[ -1.26285708e+00, -9.99999979e+33, -9.99999979e+33,
-9.99999979e+33],
[ -7.69166648e-01, -7.79999971e-01, -6.75454497e-01,
-5.95714271e-01],
[ 1.28333330e-01, -5.00000156e-02, -6.36363626e-02,
-1.41666666e-01],
[ 6.38000011e-01, 8.95384610e-01, 7.21666634e-01,
8.10000002e-01]]], dtype=float32), array([ 366.]), array([-69., -67., -65., -63.]), array([ 41., 43., 45., 47.])]
For more information, please check the documentation on using Pydap as a client. Pydap also comes with a simple server, implemented as a WSGI application. To use it, you first need to install Pydap with the server extras dependencies. If you want to serve netCDF files, install Pydap with the handlers.netcdf extra:
$ pip install Pydap[server,handlers.netcdf]
More handlers for different formats are available, if necessary. To run a simple standalone server just issue the command:
$ pydap --data ./myserver/data/ --port 8001
This will start a standalone server running on http://localhost:8001/, serving netCDF files from ./myserver/data/, similar to the test server at http://test.pydap.org/. Since the server uses the WSGI standard, it can easily be run behind Apache. The server documentation has more information on how to better deploy Pydap.
Help¶
If you need any help with Pydap, please feel free to send an email to the mailing list.