work on model_builder python; support building and testing it in python on bazel

ortools/model_builder/python/BUILD.bazel

@@ -0,0 +1,44 @@
+# Python wrapper for model_builder.
+
+load("@ortools_deps//:requirements.bzl", "requirement")
+load("@pybind11_bazel//:build_defs.bzl", "pybind_extension")
+load("@rules_python//python:defs.bzl", "py_library")
+
+pybind_extension(
+    name = "pywrap_model_builder_helper",
+    srcs = ["pywrap_model_builder_helper.cc"],
+    visibility = ["//visibility:public"],
+    deps = [
+        "//ortools/linear_solver:linear_solver_cc_proto",
+        "//ortools/linear_solver:model_exporter",
+        "//ortools/model_builder/wrappers:model_builder_helper",
+        "@com_google_absl//absl/strings",
+        "@eigen//:eigen3",
+    ],
+)
+
+py_library(
+    name = "model_builder_helper",
+    srcs = ["model_builder_helper.py"],
+    data = [
+        ":pywrap_model_builder_helper.so",
+    ],
+    visibility = ["//visibility:public"],
+    deps = [
+        requirement("numpy"),
+        "//ortools/linear_solver:linear_solver_py_pb2",
+    ],
+)
+
+py_library(
+    name = "model_builder",
+    srcs = ["model_builder.py"],
+    data = [
+        ":pywrap_model_builder_helper.so",
+    ],
+    visibility = ["//visibility:public"],
+    deps = [
+        ":model_builder_helper",
+        "//ortools/linear_solver:linear_solver_py_pb2",
+    ],
+)

ortools/model_builder/python/model_builder.py

@@ -157,7 +157,7 @@ class LinearExpr(object):
         return _Sum(self, arg)
 
     def __radd__(self, arg):
-        return self.__add(arg)
+        return self.__add__(arg)
 
     def __sub__(self, arg):
         if mbh.is_zero(arg):
@@ -219,8 +219,6 @@ class LinearExpr(object):
     def __eq__(self, arg):
         if arg is None:
             return False
-        if isinstance(self, Variable) and isinstance(arg, Variable):
-            return VarCompVar(self, arg, True)
         if mbh.is_a_number(arg):
             arg = mbh.assert_is_a_number(arg)
             return BoundedLinearExpression(self, arg, arg)
@@ -242,8 +240,6 @@ class LinearExpr(object):
             return BoundedLinearExpression(self - arg, -math.inf, 0)
 
     def __ne__(self, arg):
-        if isinstance(self, Variable) and isinstance(arg, Variable):
-            return VarCompVar(self, arg, False)
         return NotImplemented
 
     def __lt__(self, arg):
@@ -540,6 +536,25 @@ class Variable(LinearExpr):
     def objective_coefficient(self, coeff):
         return self.__helper.set_var_objective_coefficient(self.__index, coeff)
 
+    def __eq__(self, arg):
+        if arg is None:
+            return False
+        if isinstance(arg, Variable):
+            return VarCompVar(self, arg, True)
+        else:
+            if mbh.is_a_number(arg):
+                arg = mbh.assert_is_a_number(arg)
+                return BoundedLinearExpression(self, arg, arg)
+            else:
+                return BoundedLinearExpression(self - arg, 0, 0)
+
+    def __ne__(self, arg):
+        if arg is None:
+            return True
+        if isinstance(arg, Variable):
+            return VarCompVar(self, arg, False)
+        return NotImplemented
+
     def __hash__(self):
         return hash((self.__helper, self.__index))
 
@@ -559,7 +574,7 @@ class VarCompVar(object):
             return f'{self.__left} == {self.__right}'
 
     def __repr__(self):
-        return f'VarEqVar({self.__left}, {self.__right}, {self.__is_equality})'
+        return f'VarCompVar({self.__left}, {self.__right}, {self.__is_equality})'
 
     @property
     def left(self):
@@ -574,7 +589,7 @@ class VarCompVar(object):
         return self.__is_equality
 
     def __bool__(self):
-        return (self.__left == self.__right) == self.__is_equality
+        return (self.__left.index == self.__right.index) == self.__is_equality
 
 
 class BoundedLinearExpression(object):