Add package docstrings to __init__.py files

Author: pulkkins

pysteps/cascade/__init__.py

@@ -1,2 +1,4 @@
+"""Methods for constructing bandpass filters and decomposing 2d precipitation 
+fields into different spatial scales."""
 
 from .interface import get_method

pysteps/extrapolation/__init__.py

@@ -1,2 +1,5 @@
+"""Methods for advection-based extrapolation of precipitation fields. Currently 
+the module contains an implementation of the semi-Lagrangian method described 
+in :cite:`GZ2002`."""
 
 from .interface import get_method

pysteps/io/__init__.py

@@ -1,3 +1,6 @@
+"""Methods for browsing data archives, reading 2d precipitation fields and writing 
+forecasts into files."""
+
 from .interface import get_method
 from .archive import *
 from .exporters import *

pysteps/motion/__init__.py

@@ -1,2 +1,3 @@
+"""Implementations of optical flow methods."""
 
 from .interface import get_method

pysteps/noise/__init__.py

@@ -1,2 +1,5 @@
+"""Methods for generating stochastic perturbations of 2d precipitation and velocity 
+fields."""
+
 from .interface import get_method
 from . import utils

pysteps/nowcasts/__init__.py

@@ -1,2 +1,4 @@
+"""Implementations of nowcasting methods. Currently the module contains a 
+deterministic advection extrapolation method and STEPS."""
 
 from .interface import get_method

pysteps/postprocessing/__init__.py

@@ -1 +1,6 @@
+"""Methods for post-processing of forecasts. Currently the module contains 
+cumulative density function (CDF)-based matching between a forecast and the 
+target distribution and computation of mean value and exceedance probabilities 
+from forecast ensembles."""
+
 from . import ensemblestats

pysteps/timeseries/__init__.py

@@ -1 +1,3 @@
-
+"""Methods and models for time series analysis. Currently the module contains 
+implementation of an autoregressive AR(p) model and methods for estimating 
+the model parameters."""

pysteps/utils/__init__.py

@@ -1,3 +1,6 @@
+"""Utility functions for converting data values to/from different units, 
+manipulating the dimensions of precipitation fields and computing the FFT."""
+
 from .arrays import *
 from .conversion import *
 from .dimension import *

pysteps/verification/__init__.py

@@ -1,3 +1,5 @@
+"""Methods for verification of deterministic and ensemble forecasts."""
+
 from .interface import get_method
 from .detcatscores import *
 from .detcontscores import *