Add vars eqs

.style.yapf

@@ -102,7 +102,7 @@ join_multiple_lines=False
 spaces_around_default_or_named_assign=False
 
 # Use spaces around the power operator.
-spaces_around_power_operator=False
+spaces_around_power_operator=True
 
 # The number of spaces required before a trailing comment.
 spaces_before_comment=2

docs/api.rst

@@ -85,3 +85,13 @@ Physics
 
 .. automodule:: essm.equations.physics.thermodynamics
    :members:
+
+
+Internals
+=========
+
+.. automodule:: essm.variables._core
+   :members:
+
+.. automodule:: essm.equations._core
+   :members:

essm/_generator.py

@@ -155,8 +155,8 @@ def __str__(self):
             result += '\n\n__all__ = (\n{0}\n)'.format(
                 '\n'.join(
                     "    '{0}',".format(var['name']) for var in self.vars))
-        reformatted_result = FormatCode(result, style_config=STYLE_YAPF)
-        return reformatted_result[0]
+            result = FormatCode(result, style_config=STYLE_YAPF)[0]
+        return result
 
     def var(
             self,
@@ -277,8 +277,10 @@ def eq(self, name, expr, doc='', parents=None, variables=None):
 
             # Serialize the internal variables.
             writer = VariableWriter()
+            internal_variables = set()
             for variable in variables:
                 writer.var(**variable)
+                internal_variables.add(variable['name'])
             variables = re.sub(
                 r'^',
                 4 * ' ',
@@ -290,8 +292,11 @@ def eq(self, name, expr, doc='', parents=None, variables=None):
                 self._imports[key] |= value
         else:
             variables = ''
+            writer = None
+            internal_variables = set()
 
         context = {
+            '_variable_writer': writer,
             "name": name,
             "doc": doc,
             "expr": expr,
@@ -301,7 +306,8 @@ def eq(self, name, expr, doc='', parents=None, variables=None):
 
         # register all imports
         for arg in expr.args():
-            if arg in Variable.__registry__:
+            if str(arg) not in internal_variables and\
+                    arg in Variable.__registry__:
                 self._imports[Variable.__registry__[arg].__module__].add(
                     str(arg))
 

essm/equations/_core.py

@@ -31,7 +31,59 @@
 
 
 class EquationMeta(type):
-    """Equation interface."""
+    r"""Equation interface.
+
+    Defines an equation with a docstring and internal variables,
+    if needed.
+
+    Example:
+
+    .. code-block:: python
+
+       from ..variables.units import meter, second
+
+       class test(Equation):
+           \"\"\"Test equation.\"\"\"
+
+           class d(Variable):
+               \"\"\"Test variable.\"\"\"
+               unit = meter
+
+           class t(Variable):
+               \"\"\"Test variable.\"\"\"
+               unit = second
+
+           class v(Variable):
+               \"\"\"Test variable.\"\"\"
+               unit = meter/second
+
+           expr = v == d / t
+
+    :raises ValueError: if the units are inconsistent.
+
+        Example:
+
+        .. code-block:: python
+
+           from ..variables.units import meter, second
+
+           class test(Equation):
+               \"\"\"Test equation with inconsistent units.\"\"\"
+
+               class d(Variable):
+                   \"\"\"Test variable.\"\"\"
+                   unit = meter
+
+               class t(Variable):
+                   \"\"\"Test variable.\"\"\"
+                   unit = second
+
+               class v(Variable):
+                   \"\"\"Test variable.\"\"\"
+                   unit = meter/second
+
+               expr = v == d * t
+    """
 
     def __new__(cls, name, parents, dct):
         """Build and register new variable."""
@@ -76,4 +128,4 @@ def __doc__(self):
         return self.definition.__doc__
 
 
-__all__ = ('Equation', )
+__all__ = ('Equation', 'EquationMeta')

essm/style.yapf

@@ -102,7 +102,7 @@ join_multiple_lines=False
 spaces_around_default_or_named_assign=False
 
 # Use spaces around the power operator.
-spaces_around_power_operator=False
+spaces_around_power_operator=True
 
 # The number of spaces required before a trailing comment.
 spaces_before_comment=2

tests/test_equations.py

@@ -3,10 +3,11 @@
 
 import pytest
 
+from essm._generator import EquationWriter
 from essm.equations import Equation
 from essm.variables import Variable
 from essm.variables.units import joule, kelvin, meter, mole, second
-from sage.all import solve
+from sage.all import solve, var
 
 
 class demo_g(Variable):
@@ -93,3 +94,27 @@ class demo_double(Equation):  # ignore: W0232
             expr = demo_g = demo_g
 
     assert Equation.__registry__[demo_double].__doc__ == 'Second.'
+
+
+def test_equation_writer(tmpdir):
+    """EquationWriter creates importable file with internal variables."""
+    g = {}
+    d = var('d')
+    t = var('t')
+    writer_td = EquationWriter(docstring='Test of Equation_writer.')
+    writer_td.eq(
+        'demo_fall',
+        demo_g == d / t ** 2,
+        doc='Test equation.\n\n    (Some reference)\n    ',
+        variables=[{
+            "name": "d",
+            "value": '0.9',
+            "units": meter,
+            "latexname": 'p_1'}, {
+                "name": "t",
+                "units": second,
+                "latexname": 'p_2'}])
+    eq_file = tmpdir.mkdir('test').join('test_equations.py')
+    writer_td.write(eq_file.strpath)
+    execfile(eq_file.strpath, g)
+    assert g['demo_fall'].definition.d.definition.default == 0.9