Merge pull request #2834 from ERGO-Code/modelling-doc

Introduced `model-py.md` and `chip0.py`

Author: jajhall

docs/make.jl

@@ -88,6 +88,7 @@ Documenter.makedocs(
             "Python" => Any[
                 "interfaces/python/index.md",
                 "interfaces/python/example-py.md",
+                "interfaces/python/model-py.md",
             ],
             "CSharp" => "interfaces/csharp.md",
             "Julia" => "interfaces/julia/index.md",

docs/src/interfaces/python/index.md

@@ -18,13 +18,6 @@ To use `highspy` within a Python program, it must be imported
 import highspy
 ```
 
-When using `highspy`, it is likely that `numpy` structures will be needed,
-so must also be imported
-
-```python
-import numpy as np
-```
-
 ## Initialize
 
 HiGHS must be initialized before making calls to the HiGHS Python library:

docs/src/interfaces/python/model-py.md

@@ -0,0 +1,90 @@
+# [Modelling](@id model-py)
+
+HiGHS has a rudimentry modelling language that allows models to be built and run using `highspy`. 
+
+Below is an example of building a mathematical LP. The functions used are documented in detail below
+```
+# model and solve the LP
+#
+# maximize 10 x1 + 25x2
+# s. t.       x1 +  2x2 <=  80
+#             x1 +  4x2 <= 120
+#             x1 >= 0; x2 >= 0
+import highspy
+
+h = highspy.Highs()
+
+x1 = h.addVar()
+x2 = h.addVar()
+
+h.addConstr(x1 + 2*x2 <=  80)
+h.addConstr(x1 + 4*x2 <= 120)
+
+h.maximize(10*x1 + 25*x2)
+
+print("x1 = ", h.val(x1))
+print("x2 = ", h.val(x2))
+```
+
+## addVar
+
+Adds a variable to the model. By default it is continuous,
+non-negative, with zero objective coefficient, and has no name
+associated with it.
+
+```
+addVar(lb = 0, ub = kHighsInf, obj = 0, type=HighsVarType.kContinuous, name = None)
+```
+
+## addConstr
+
+Adds a constraint to the model. It must be defined in terms of a
+linear function, with `*` used when there are non-unit
+coefficients. By default it has a lower bound of -infinity, an upper
+bound of +infinity, and no name associated with it.
+
+```
+addConstr(cons, name = None)
+```
+
+## maximize
+
+Calls HiGHS to maximize the objective. By default it uses the
+objective coefficients defined when the variables were added to the
+model. However, a linear function can be passed as an argument.
+
+```
+maximize(obj=None)
+```
+
+## minimize
+
+Calls HiGHS to minimize the objective. By default it uses the
+objective coefficients defined when the variables were added to the
+model. However, a linear function can be passed as an argument.
+
+```
+minimize(obj=None)
+```
+
+## val
+
+Extracts the current value of a particular variable
+
+```
+val(var)
+```
+
+## vals
+
+Extracts the current values of a particular set of variables
+
+```
+vals(vars)
+```
+
+## MIP Example
+
+
+
+

examples/chip0.py

@@ -0,0 +1,29 @@
+# model and solve the LP
+#
+# maximize 10 x1 + 25x2
+# s. t.       x1 +  2x2 <= 80
+#             x1 +  4x2 <= 120
+#             x1 >= 0; x2 >= 0
+import highspy
+
+h = highspy.Highs()
+
+x1 = h.addVar(obj = 10)
+x2 = h.addVar(obj = 25)
+
+h.addConstr(x1 + 2*x2 <= 80)
+h.addConstr(x1 + 4*x2 <= 120)
+
+h.writeModel("")
+print("x1 = ", h.val(x1))
+print("x2 = ", h.val(x2))
+
+h.maximize()
+
+print("x1 = ", h.val(x1))
+print("x2 = ", h.val(x2))
+
+print("x = ", h.vals([x1, x2]))
+
+
+