Add package_tools module for exporter

examples/umetpy_simpletest.py

@@ -3,12 +3,10 @@
 #
 # SPDX-License-Identifier: BSD-3-Clause
 
-import umetpy.constants
+import umetpy.constants as mpconsts
 
 # pylint: disable=eval-used
 print("List of all constants:\n")
-for cst in dir(umetpy.constants):
+for cst in dir(mpconsts):
     if cst[0] != "_":
-        print(
+        print("{:30s} = {:.12f}".format(cst, eval("{}.{}".format("mpconsts", cst))))
-            "{:25s} = {:f}".format(cst, eval("{}.{}".format("umetpy.constants", cst)))
-        )

umetpy/constants.py

@@ -4,7 +4,7 @@
 
 # pylint: disable=line-too-long
 
-r"""A collection of meteorologically significant constant and thermophysical property values.
+r"""A collection of meteorologically significant constants and thermophysical property values.
 
 Earth
 -----
@@ -75,7 +75,12 @@ molecular_weight_ratio   :math:`\epsilon`  epsilon     :math:`\text{None}`
 # pylint: enable=line-too-long
 
 # pylint: disable=invalid-name
+from .package_tools import Exporter
 
+exporter = Exporter(globals())
+
+# Export all the variables defined in this block
+with exporter:
     # Earth
     earth_gravity = g = 9.80665  # 'm / s^2'
     Re = earth_avg_radius = 6371008.7714  # 'm'
@@ -115,7 +120,7 @@ Cp_d = dry_air_spec_heat_press = (
     )
     Cv_d = dry_air_spec_heat_vol = Cp_d / dry_air_spec_heat_ratio
     # TODO : check unit conversion
-# rho_d = dry_air_density_stp = (1000., 'mbar') / (Rd * 273.15, 'K')))  # 'kg / m^3'
+    rho_d = dry_air_density_stp = 1000.0 / (Rd * 273.15)  # 'kg / m^3'
 
     # General meteorology constants
     P0 = pot_temp_ref_press = 1000.0  # 'mbar'
@@ -124,3 +129,6 @@ kappa = poisson_exponent = Rd / Cp_d  # 'dimensionless'
     gamma_d = dry_adiabatic_lapse_rate = g / Cp_d
     # TODO : check unit conversion
     epsilon = molecular_weight_ratio = Mw / Md  # 'dimensionless'
+
+del exporter
+del Exporter

umetpy/package_tools.py

@@ -0,0 +1,63 @@
+# Copyright (c) 2015,2018,2019 MetPy Developers.
+# Distributed under the terms of the BSD 3-Clause License.
+# SPDX-License-Identifier: BSD-3-Clause
+"""Collection of tools for managing the package."""
+
+# Used to specify functions that should be exported--i.e. added to __all__
+# Inspired by David Beazley and taken from python-ideas:
+# https://mail.python.org/pipermail/python-ideas/2014-May/027824.html
+
+__all__ = ("Exporter",)
+
+
+class Exporter:
+    """Manages exporting of symbols from the module.
+
+    Grabs a reference to `globals()` for a module and provides a decorator to add
+    functions and classes to `__all__` rather than requiring a separately maintained list.
+    Also provides a context manager to do this for instances by adding all instances added
+    within a block to `__all__`.
+    """
+
+    def __init__(self, globls):
+        """Initialize the Exporter."""
+        self.globls = globls
+        self.exports = globls.setdefault("__all__", [])
+
+    def export(self, defn):
+        """Declare a function or class as exported."""
+        self.exports.append(defn.__name__)
+        return defn
+
+    def __enter__(self):
+        """Start a block tracking all instances created at global scope."""
+        # pylint: disable=attribute-defined-outside-init
+        self.start_vars = set(self.globls)
+        # pylint: enable=attribute-defined-outside-init
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        """Exit the instance tracking block."""
+        self.exports.extend(set(self.globls) - self.start_vars)
+        del self.start_vars
+
+
+def set_module(globls):
+    """Set the module for all functions in ``__all__``.
+
+    This sets the ``__module__`` attribute of all items within the ``__all__`` list
+    for the calling module.
+
+    This supports our hoisting of functions out of individual modules, which are
+    considered implementation details, into the namespace of the top-level subpackage.
+
+    Parameters
+    ----------
+    globls : Dict[str, object]
+        Mapping of all global variables for the module. This contains all needed
+        python special ("dunder") variables needed to be modified.
+
+    """
+    for item in globls["__all__"]:
+        obj = globls[item]
+        if hasattr(obj, "__module__"):
+            obj.__module__ = globls["__name__"]