Using pysat as a dependency

Instrument Libraries

Say you are developing an instrument library under the name customLibrary, which has two instrument objects. A minimalist structure for the library could look something like:

|   |-- docs
|   |   `-- tutorial.rst
|   |-- instruments
|   |   |--
|   |   |--
|   |   |--
|   |-- tests
|   |   |--
|   |   `--
|   `--

The instruments folder includes a file for each instrument object. The requirements for structuring each of the instruments is discussed in Adding a New Instrument. The __init__ file in this folder should import the instruments and construct a list of instruments to aid in the testing.

from customLibrary.instruments import lib_inst1, lib_inst2

__all__ = ['lib_inst1', 'lib_inst2']

The tests folder contains an empty __init__ file to be compliant with pytest and the test_instruments script. pysat includes a standard suite of instrument tests to run on instruments. These are imported from the instrument_test_class in the main pysat test library. The file can be copied directly into the library, updating the instrument library name as indicated.

The file should include pysat as a dependency, as well as any other packages required by the instruments.

A more complicated structure could include analysis routines, like the pysatModels package, or methods for common analysis routines used for a specific data set, like the pysatMadrigal package. The structure then could look like:

|   |-- docs
|   |   `-- tutorial.rst
|   |-- instruments
|   |   |--
|   |   |--
|   |   |--
|   |   |-- methods
|   |   |   |--
|   |   |   |--
|   |   |   `--
|   |-- tests
|   |   |--
|   |   `--
|   |-- utils
|   |   |--
|   |   |--
|   |   `--
|   `--

Using pysat to test your instruments

A generalized instrument test class is provided under pysat.tests for developers. Continuing the above example, developers may copy over the file and update it in a few locations. For example

# Make sure to import your instrument library here
import customLibrary

# Import the test classes from pysat
from pysat.tests.instrument_test_class import generate_instrument_list
from pysat.tests.instrument_test_class import InstTestClass

# Developers for instrument libraries should update the following line to
# point to their own library location. For example,
# instruments = generate_instrument_list(inst_loc=mypackage.instruments)
instruments = generate_instrument_list(inst_loc=customLibrary.instruments)

The above code scans the list of instruments and flags each instrument for one or more of the test types, as defined below. This bit of the code should generally be unchanged. Instruments are grouped in three lists:

  • instruments[‘names’]: A list of all module names to check for standardization
  • instruments[‘download’]: A list of dicts containing info to initialize instruments for end-to-end testing
  • instruments[‘no_download’]: A list of dicts containing info to initialize instruments without download support for specialized local tests
# The following lines apply the custom instrument lists to each type of test
method_list = [func for func in dir(InstTestClass)
               if callable(getattr(InstTestClass, func))]
# Search tests for iteration via pytestmark, update instrument list
for method in method_list:
    if hasattr(getattr(InstTestClass, method), 'pytestmark'):
        # Get list of names of pytestmarks
        nargs = len(getattr(InstTestClass, method).pytestmark)
        names = [getattr(InstTestClass, method).pytestmark[j].name
                 for j in range(0, nargs)]
        # Add instruments from your library
        if 'all_inst' in names:
            mark = pytest.mark.parametrize("inst_name", instruments['names'])
            getattr(InstTestClass, method).pytestmark.append(mark)
        elif 'download' in names:
            mark = pytest.mark.parametrize("inst_dict",
            getattr(InstTestClass, method).pytestmark.append(mark)
        elif 'no_download' in names:
            mark = pytest.mark.parametrize("inst_dict",
            getattr(InstTestClass, method).pytestmark.append(mark)

Finally, the setup_class function under the TestInstruments class should be updated with the location of the instrument subpackage. Note that the routine uses temporary directories to store downloaded files to avoid breaking user’s directory structure.

class TestInstruments(InstTestClass):
    """Uses class level setup and teardown so that all tests use the same
    temporary directory. We do not want to geneate a new tempdir for each test,
    as the load tests need to be the same as the download tests.

  def setup_class(self):
      """Runs once before the tests to initialize the testing setup."""
      # Make sure to use a temporary directory so that the user's setup is not
      # altered
      self.tempdir = tempfile.TemporaryDirectory()
      self.saved_path = pysat.params['data_dirs']
      pysat.params['data_dirs'] =
      # Developers for instrument libraries should update the following line
      # to point to their own subpackage location, e.g.,
      # self.inst_loc = mypackage.instruments
      self.inst_loc = pysat.instruments

  def teardown_class(self):
      """Runs once to clean up testing from this class."""
      pysat.params['data_dirs'] = self.saved_path
      del self.inst_loc, self.saved_path, self.tempdir

Testing custom analysis routines

What if you are developing analysis routines or instruments with special functions? pysat includes a series of test instrument objects that can be imported by other packages to test those functions. For instance, pysatModels contains a series of routines to collect similar measurements between instruments and models. The test instruments are used as part of the unit tests. This allows us to thoroughly test routines without including a large volume of data as part of the package.


pysat_testing is the basic test object. It returns a satellite-like object with 1D data as a function of latitude, longitude, and altitude in a pandas format. Most similar to in situ data.


pysat_testing_xarray returns a satellite-like object with 1D data as a function of latitude, longitude, and altitude in a xarray format.


pysat_testing2d is another satellite-like object that also returns profile data as a function of altitude at some distance from the satellite. It is similar to a Radio Occultation or other instruments that have altitude profiles.


pysat_testing2d_xarray is a satellite-like object that returns all of the above plus an imager-like data set, ie, remote data that is a function of time and two spatial dimensions.


pysat_testmodel is an xarray object that returns a 4D object as a function of latitude, longitude, altitude, and time. It most closely resembles data sets from geophysical models.

All of these objects return dummy data values that are either constants or small periodic variations. The intent of these objects are to return data sets that resemble instrument data in scope.

A very basic example is shown below. Here a stats library is imported from the custom instrument. The dummy1 variable is a simple data set that returns values between 0 and 20.

import pysat

from customLibrary import stats

class TestCompare:

  def setup(self):
      self.inst = pysat.Instrument(platform='pysat', name='testing')
      self.inst.load(2009, 1)

  def teardown(self):
      del self.inst

  def test_stats_mean(self):
      mean_val = stats.mean(inst['dummy1'])
      assert mean_val == 11.3785

The setup function is used to define and load a fresh instrument for each test. While data are automatically generated, limits on the usable range have been imposed for testing purposes. The test instruments generate dates between 1 Jan 2008 and 31 Dec 2010 for use in the pysat ecosystem. This allows for coverage for year changes both with and without leap days.

Tips and Tricks

Remember to include pysat as a dependency in your or setup.cfg file.

The CI environment will also need to be configured to install pysat and its dependencies. You may need to install pysat from github rather than pip if you need to test against a specific development branch.