README.rst

pyds

Python interface to NASA's PDS (Planetary Data System) labels.

Dependencies

• Python 3.4+

Documentation

Documentation is available at http://pyds.sohi.link

Usage

Here's a quick overview on how to use the module. Refer to the documentation for more details.

First, parse the PDS label:

import pyds
import mmap

# Use a mmap to avoid loading the entire file into memory
fobj = open("path/to/label.img", "rb")
fobj_mm = mmap.mmap(fobj.fileno(), 0)

label = pyds.parse(fobj_mm)

Then, use the label object to access different attributes of the label:

# Get the total number of statements
len(label)

# Get a statement by index
label.get(1)

# Get a statement's identifier
label.get(1).identifier

# Get a statement's value
label.get(1).value

# Get a statement's value by its identifier
label["key"]

# Get nested values of PDS groups and objects
label["a"]["b"]["c"]

# Check if a statement exists with the given identifier
"a" in label
"b" in label["a"]

Similarly, the label object can also be modified:

# Append/insert a statement by index
label.append(pyds.Attribute("pi", pyds.Real(3.14)))
label.insert(-1, pyds.Attribute("e", pyds.Real(2.71)))

# Append a statement using a new identifier
label["new_ident"] = pyds.Integer(10)

# Change a statement's value using its identifier
label["old_ident"] = pyds.Integer(7)

# Change nested values of PDS groups and objects
label["a"]["b"]["c"] = pyds.Integer(5)

# Remove a statement by index
label.pop(1)

# Remove a statement by its identifier
del label["a"]
del label["a"]["b"]["c"]

Finally, to save the label, serialize the label object to a PDS byte string:

bytes(label)