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Description:

pydap 3.5

pydap

pydap is an implementation of the
Opendap/DODS protocol, written from scratch in pure python. You can
use pydap to access scientific data on the internet without having to
download it; instead, you work with special array and iterable objects
that download data on-the-fly as necessary, saving bandwidth and
time. The module also comes with a robust-but-lightweight Opendap
server, implemented as a WSGI application.
Quickstart
pydap is a lighweight python package that you can use in either
of the two modalities: a client and as a server.
You can install the latest version 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. pydap is also available through Anaconda.
Below we install pydap and its required dependencies, along with common
additional packages in a fresh conda environment named pydap:
$ mamba create -n pydap -c conda-forge python=3.10 pydap numpy jupyterlab ipython netCDF4 scipy matplotlib

Now you simply activate the pydap environment:
mamba activate pydap

You can now use pydap as a client and 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 the server and
optionally a data handler:
$ pip install "pydap[server,handlers.netcdf]"

This will install support for
netCDF files; more
handlers for
different formats are available, if necessary. Now create a directory
for your server data.
To run the server just issue the command:
$ pydap --data ./myserver/data/ --port 8001 --workers 4 --threads 4

This will start a standalone server running on the default 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, pydap uses by default 1 worker and 1
thread, but these can be defined by the user like in the case above (4 workers
and 4 threads). Pydap can also easily be run behind Apache. The server
documentation has
more information on how to better deploy pydap.
Documentation
For more information, see the pydap
documentation.
Help
If you need any help with pydap, please feel free to send an email to
the mailing list