Introduction to sdss_access¶

Path Generation¶

You can generate full paths to files easily with Path.full:

# import the path
from sdss_access import SDSSPath
path = SDSSPath()

# generate a file system path
path.full('mangacube', drpver='v2_3_1', plate='8485', ifu='1901')
'/Users/Brian/Work/sdss/sas/mangawork/manga/spectro/redux/v2_3_1/8485/stack/manga-8485-1902-LOGCUBE.fits.gz'

Note that this only generates a path. The file may not actually exist locally. If you want to generate a URL path to the file at Utah, you can use Path.url:

# generate a http path to the file
path.url('mangacube', drpver='v2_3_1', plate='8485', ifu='1901')
'https://data.sdss.org/sas/mangawork/manga/spectro/redux/v2_3_1/8485/stack/manga-8485-1902-LOGCUBE.fits.gz'

Path Names¶

The syntax for all paths defined in sdss_access, for most methods, is (name, **kwargs). Each path is defined by a name and several keyword arguments, indicated in the template filepath by {keyword_name}. For example, the path to a MaNGA data cube has name mangacube and path keywords, plate, drpver, and ifu, defined in the path $MANGA_SPECTRO_REDUX/{drpver}/{plate}/stack/manga-{plate}-{ifu}-LOGCUBE.fits.gz. All paths are defined inside the SDSS tree product, within the sdss_paths.ini file, and available to you as a dictionary, path.templates:

from sdss_access import SDSSPath
path = SDSSPath()

# show the dictionary of available paths
path.templates

To look up what path names are available, you can use path.lookup_names:

# look up the available path names
path.lookup_names()
['BOSSLyaDR_cat', ..., 'mangacube', ..., 'xdqso_index']

To look up what keywords are needed for a given path, you can use path.lookup_keys:

# look up the keyword arguments needed to define a MaNGA cube path
path.lookup_keys('mangacube')
['plate', 'drpver', 'ifu']

The full list of paths can also be found here.

Downloading Files¶

You can download files from the SAS and place them in your local SAS. sdss_access expects a local SAS filesystem that mimics the real SAS at Utah. If you do not already have a SAS_BASE_DIR set, one will be defined in your home directory, as a new sas directory.

Using the HttpAccess package.

from sdss_access import HttpAccess
http_access = HttpAccess(verbose=True)

# set to use remote
http_access.remote()

# get the file
http_access.get('mangacube', drpver='v2_3_1', plate='8485', ifu='1901')

Using the RsyncAccess package. RsyncAccess is generally much faster then HttpAccess as it spreads multiple file downloads across multiple continuous rsync download streams.

# import the rsync package
from sdss_access import RsyncAccess
rsync = RsyncAccess()

# sets a remote mode to the real SAS
rsync.remote()

# add all the file(s) you want to download
# let's download all MPL-6 MaNGA cubes for plate 8485
rsync.add('mangacube', drpver='v2_3_1', plate='8485', ifu='*')

# set the stream tasks
rsync.set_stream()

# start the download(s)
rsync.commit()

The default mode of RsyncAccess is for collaboration access. You can also access data from publicly available SDSS data releases, by specifying the public and release keyword arguments on init.

# setup rsync access to download public data from DR14
rsync = RsyncAccess(public=True, release='dr14')

Reference/API¶

Class

Methods