Siphon

0.10.0 verified Mon Apr 27 auth: no python

Siphon is a collection of Python utilities for interacting with the Unidata technology stack, particularly for accessing and downloading remote datasets via THREDDS Data Servers (TDS). Current version 0.10.0 requires Python >=3.10. Releases are periodic, roughly yearly.

pip install siphon

Common errors

error ModuleNotFoundError: No module named 'siphon' ↓

cause Siphon is not installed or installed in a different environment.

fix

Run 'pip install siphon' in the correct Python environment.

error AttributeError: module 'siphon' has no attribute 'TDSCatalog' ↓

cause TDSCatalog is not in the top-level siphon module.

fix

Use 'from siphon.catalog import TDSCatalog'.

error requests.exceptions.ConnectionError: HTTPSConnectionPool ↓

cause Network issue or incorrect URL when accessing a THREDDS server.

fix

Verify the catalog URL is correct and reachable. Use 'https://thredds.ucar.edu/thredds/catalog.xml' as a test.

Warnings

breaking Siphon 0.9.0 dropped support for Python 2.7 and older Python 3.x. Python >=3.6 required; from 0.10.0, Python >=3.10 required. ↓

fix Use Python 3.10 or newer for siphon >=0.10.0.

deprecated The 'siphon.cdmr' module is deprecated as of siphon 0.9.0 and may be removed in a future release. ↓

fix Migrate to using 'siphon.ncss' or direct NetCDF4 access via remote_open.

gotcha When using TDSCatalog with a remote server, ensure the URL points to a valid catalog.xml, not a dataset access URL. Otherwise, parsing may fail silently. ↓

fix Append '/catalog.xml' to the base THREDDS server URL if not already present.

Imports

TDSCatalog
wrong
```
from siphon import TDSCatalog
```
correct
```
from siphon.catalog import TDSCatalog
```
TDSCatalog is not in the top-level siphon namespace; must import from siphon.catalog.
NCSS
wrong
```
from siphon import NCSS
```
correct
```
from siphon.ncss import NCSS
```
NCSS (NetCDF Subset Service) is in siphon.ncss.
remote_open
```
from siphon.ncss import remote_open
```
remote_open is a utility function in the ncss module.

Quickstart

Connects to a THREDDS Data Server catalog and lists available datasets.

from siphon.catalog import TDSCatalog

# Create a catalog object for the Unidata THREDDS server
cat = TDSCatalog('https://thredds.ucar.edu/thredds/catalog.xml')
# List datasets
print(list(cat.datasets)[:5])