cleanups, null default for freezing spectrum, README update

PySDM/environments/box.py

@@ -18,7 +18,10 @@ def __getitem__(self, item):
         return self._ambient_air[item]
 
     def __setitem__(self, key, value):
-        self._ambient_air[key] = self.particulator.backend.Storage.from_ndarray(np.array([value]))
+        if key not in self._ambient_air:
+            self._ambient_air[key] = self.particulator.backend.Storage.from_ndarray(np.array([value]))
+        else:
+            self._ambient_air[key][:] = value
 
     def register(self, builder):
         self.particulator = builder.particulator

PySDM/initialisation/multiplicities.py

@@ -12,6 +12,6 @@ def discretise_n(y_float):
         raise Exception(f"{percent_diff}% error in total real-droplet number due to casting multiplicities to ints")
 
     if not (y_int > 0).all():
-        raise Exception("int-casting resulted in multiplicity of zero")
+        raise Exception(f"int-casting resulted in multiplicity of zero (min(y_float)={min(y_float)})")
 
     return y_int

PySDM/physics/formulae.py

@@ -65,7 +65,7 @@ def _pick(value: str, choices: dict):
     for name, cls in choices.items():
         if name == value:
             return cls()
-    raise ValueError(f"Unknown setting: '{value}';, choices are: {tuple(choices.keys())}")
+    raise ValueError(f"Unknown setting: '{value}'; choices are: {tuple(choices.keys())}")
 
 
 def _choices(module):
@@ -93,7 +93,7 @@ def __init__(self, *,
                  state_variable_triplet: str = 'RhodThdQv',
                  particle_advection: str = 'ImplicitInSpace',
                  hydrostatics: str = 'Default',
-                 freezing_temperature_spectrum: str = 'Niemand_et_al_2012',
+                 freezing_temperature_spectrum: str = 'Null',
                  heterogeneous_ice_nucleation_rate: str = 'Null'
                  ):
         self.seed = seed

PySDM/physics/freezing_temperature_spectrum/null.py

@@ -0,0 +1,2 @@
+class Null:
+    pass

PySDM/products/product.py

@@ -79,14 +79,14 @@ def __init__(self, **args):
         self.source = None
 
     def register(self, builder):
-        assert isinstance(builder.particulator.env, _Moist)
         super().register(builder)
         self.particulator.observers.append(self)
         self.environment = builder.particulator.env
         self.source = self.environment[self._name]
 
     def notify(self):
-        self.source = self.environment.get_predicted(self._name)
+        if isinstance(self.environment, _Moist):
+            self.source = self.environment.get_predicted(self._name)
 
     def get(self):
         self.download_to_buffer(self.source)

PySDM/state/particles.py

@@ -76,6 +76,9 @@ def keys(self):
     def __getitem__(self, item):
         return self.attributes[item].get()
 
+    def __contains__(self, key):
+        return key in self.attributes
+
     def permutation(self, u01, local):
         if local:
             """

README.md

@@ -602,7 +602,8 @@ the license of the contributed code must be compatible with GPL v3.
 
 Developing the code, we follow [The Way of Python](https://www.python.org/dev/peps/pep-0020/) and 
 the [KISS principle](https://en.wikipedia.org/wiki/KISS_principle).
-The codebase has greatly benefited from [PyCharm code inspections](https://www.jetbrains.com/help/pycharm/code-inspection.html).
+The codebase has greatly benefited from [PyCharm code inspections](https://www.jetbrains.com/help/pycharm/code-inspection.html)
+and [Pylint](https://pylint.org) code analysis (which constitutes one of the CI workflows).
 
 Issues regarding any incorrect, unintuitive or undocumented bahaviour of
 PySDM are best to be reported on the [GitHub issue tracker](https://github.com/atmos-cloud-sim-uj/PySDM/issues/new).
@@ -616,10 +617,24 @@ We look forward to your contributions and feedback.
 
 ## Credits:
 
-Development of PySDM is supported by the EU through a grant of the Foundation for Polish Science (POIR.04.04.00-00-5E1C/18).
-
-copyright: Jagiellonian University   
-licence: GPL v3   
+The development and maintenance of PySDM is led by [Sylwester Arabas](https://github.com/slayoo/).
+[Piotr Bartman](https://github.com/piotrbartman/) had been the architect and main developer 
+of technological solutions in PySDM. 
+The suite of examples shipped with PySDM includes contributions from researchers 
+from [Jagiellonian University](https://en.uj.edu.pl/en) departments of computer science, physics and chemistry;
+and from 
+[Caltech's Climate Modelling Alliance](https://clima.caltech.edu/).
+
+Development of PySDM had been initially supported by the EU through a grant of the 
+[Foundation for Polish Science](https://www.fnp.org.pl/)) (POIR.04.04.00-00-5E1C/18) 
+realised at the [Jagiellonian University](https://en.uj.edu.pl/en).
+The immersion freezing support in PySDM is developed with support from the
+US Department of Energy [Atmospheric System Research](https://asr.science.energy.gov/) programme
+through a grant realised at the 
+[University of Illinois at Urbana-Champaign](https://illinois.edu/).
+
+copyright: [Jagiellonian University](https://en.uj.edu.pl/en)    
+licence: [GPL v3](https://www.gnu.org/licenses/gpl-3.0.html)
 
 ## Related resources and open-source projects