satpy.utils module

Module defining various utilities.

exception satpy.utils.PerformanceWarning

Bases: Warning

Warning raised when there is a possible performance impact.

satpy.utils.angle2xyz(azi, zen)

Convert azimuth and zenith to cartesian.

satpy.utils.atmospheric_path_length_correction(data, cos_zen, limit=88.0, max_sza=95.0)

Perform Sun zenith angle correction.

This function uses the correction method proposed by Li and Shibata (2006): https://doi.org/10.1175/JAS3682.1

The correction is limited to limit degrees (default: 88.0 degrees). For larger zenith angles, the correction is the same as at the limit if max_sza is None. The default behavior is to gradually reduce the correction past limit degrees up to max_sza where the correction becomes 0. Both data and cos_zen should be 2D arrays of the same shape.

satpy.utils.check_satpy(readers=None, writers=None, extras=None)

Check the satpy readers and writers for correct installation.

Parameters

• readers (list or None) – Limit readers checked to those specified

• writers (list or None) – Limit writers checked to those specified

• extras (list or None) – Limit extras checked to those specified

Returns: bool

True if all specified features were successfully loaded.

satpy.utils.convert_remote_files_to_fsspec(filenames, storage_options=None)

Check filenames for transfer protocols, convert to FSFile objects if possible.

satpy.utils.debug(deprecation_warnings=True)

Context manager to temporarily set debugging on.

Example:

>>> with satpy.utils.debug():
...     code_here()

Parameters

deprecation_warnings (Optional[bool]) – Switch on deprecation warnings. Defaults to True.

satpy.utils.debug_off()

Turn debugging logging off.

This disables both debugging logging and the global visibility of deprecation warnings.

satpy.utils.debug_on(deprecation_warnings=True)

Turn debugging logging on.

Sets up a StreamHandler to to sys.stderr at debug level for all loggers, such that all debug messages (and log messages with higher severity) are logged to the standard error stream.

By default, since Satpy 0.26, this also enables the global visibility of deprecation warnings. This can be suppressed by passing a false value.

Parameters

deprecation_warnings (Optional[bool]) – Switch on deprecation warnings. Defaults to True.

Returns

None

satpy.utils.deprecation_warnings_off()

Switch off deprecation warnings.

satpy.utils.deprecation_warnings_on()

Switch on deprecation warnings.

satpy.utils.find_in_ancillary(data, dataset)

Find a dataset by name in the ancillary vars of another dataset.

Parameters

• data (xarray.DataArray) – Array for which to search the ancillary variables

• dataset (str) – Name of ancillary variable to look for.

satpy.utils.get_chunk_pixel_size()

Compute the maximum chunk size from CHUNK_SIZE.

satpy.utils.get_chunk_size_limit(dtype)

Compute the chunk size limit in bytes given dtype.

Returns

If PYTROLL_CHUNK_SIZE is not defined, this function returns None, otherwise it returns the computed chunk size in bytes.

satpy.utils.get_logger(name)

Return logger with null handler added if needed.

satpy.utils.get_satpos(data_arr: DataArray, preference: Optional[str] = None, use_tle: bool = False) → tuple[float, float, float]

Get satellite position from dataset attributes.

Parameters

• data_arr – DataArray object to access .attrs metadata from.

• preference –

  Optional preference for one of the available types of position information. If not provided or None then the default preference is:

  • Longitude & Latitude: nadir, actual, nominal, projection

  • Altitude: actual, nominal, projection

  The provided preference can be any one of these individual strings (nadir, actual, nominal, projection). If the preference is not available then the original preference list is used. A warning is issued when projection values have to be used because nothing else is available and it wasn’t provided as the preference.

• use_tle – If true, try to obtain position via satellite name and TLE if it can’t be determined otherwise. This requires pyorbital, skyfield, and astropy to be installed and may need network access to obtain the TLE. Note that even if use_tle is true, the TLE will not be used if the dataset metadata contain the satellite position directly.

Returns

Geodetic longitude, latitude, altitude [km]

satpy.utils.get_storage_options_from_reader_kwargs(reader_kwargs)

Read and clean storage options from reader_kwargs.

satpy.utils.ignore_invalid_float_warnings()

Ignore warnings generated for working with NaN/inf values.

Numpy and dask sometimes don’t like NaN or inf values in normal function calls. This context manager hides/ignores them inside its context.

Examples

Use around numpy operations that you expect to produce warnings:

with ignore_invalid_float_warnings():
    np.nanmean(np.nan)

satpy.utils.import_error_helper(dependency_name)

Give more info on an import error.

satpy.utils.in_ipynb()

Check if we are in a jupyter notebook.

satpy.utils.logging_off()

Turn logging off.

satpy.utils.logging_on(level=30)

Turn logging on.

satpy.utils.lonlat2xyz(lon, lat)

Convert lon lat to cartesian.

For a sphere with unit radius, convert the spherical coordinates longitude and latitude to cartesian coordinates.

Parameters

• lon (number or array of numbers) – Longitude in °.

• lat (number or array of numbers) – Latitude in °.

Returns

(x, y, z) Cartesian coordinates [1]

satpy.utils.proj_units_to_meters(proj_str)

Convert projection units from kilometers to meters.

satpy.utils.recursive_dict_update(d, u)

Recursive dictionary update.

Copied from:

http://stackoverflow.com/questions/3232943/update-value-of-a-nested-dictionary-of-varying-depth

satpy.utils.trace_on()

Turn trace logging on.

satpy.utils.unify_chunks(*data_arrays: DataArray) → tuple[xarray.core.dataarray.DataArray, ...]

Run xarray.unify_chunks() if input dimensions are all the same size.

This is mostly used in satpy.composites.CompositeBase to safe guard against running dask.array.core.map_blocks() with arrays of different chunk sizes. Doing so can cause unexpected results or errors. However, xarray’s unify_chunks will raise an exception if dimensions of the provided DataArrays are different sizes. This is a common case for Satpy. For example, the “bands” dimension may be 1 (L), 2 (LA), 3 (RGB), or 4 (RGBA) for most compositor operations that combine other composites together.

satpy.utils.xyz2angle(x, y, z, acos=False)

Convert cartesian to azimuth and zenith.

satpy.utils.xyz2lonlat(x, y, z, asin=False)

Convert cartesian to lon lat.

For a sphere with unit radius, convert cartesian coordinates to spherical coordinates longitude and latitude.

Parameters

• x (number or array of numbers) – x-coordinate, unitless

• y (number or array of numbers) – y-coordinate, unitless

• z (number or array of numbers) – z-coordinate, unitless

• asin (optional, bool) – If true, use arcsin for calculations. If false, use arctan2 for calculations.

Returns

Longitude and latitude in °.

Return type

(lon, lat)