Add PyCall extension

.github/workflows/CI.yml

@@ -18,6 +18,7 @@ jobs:
         group:
           - Core
           - Downstream
+          - Python
         version:
           - '1'
     steps:

Project.toml

@@ -33,9 +33,11 @@ TruncatedStacktraces = "781d530d-4396-4725-bb49-402e4bee1e77"
 ZygoteRules = "700de1a5-db45-46bc-99cf-38207098b444"
 
 [weakdeps]
+PyCall = "438e738f-606a-5dbb-bf0a-cddfbfd45ab0"
 Zygote = "e88e6eb3-aa80-5325-afca-941959d7151f"
 
 [extensions]
+PyCallExt = "PyCall"
 ZygoteExt = "Zygote"
 
 [compat]
@@ -69,11 +71,12 @@ Aqua = "4c88cf16-eb10-579e-8560-4a9242c79595"
 DelayDiffEq = "bcd4f6db-9728-5f36-b5f7-82caef46ccdb"
 OrdinaryDiffEq = "1dea7af3-3e70-54e6-95c3-0bf5283fa5ed"
 Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
+PyCall = "438e738f-606a-5dbb-bf0a-cddfbfd45ab0"
 SafeTestsets = "1bc83da4-3b8d-516f-aca4-4fe02f6d838f"
 StaticArrays = "90137ffa-7385-5640-81b9-e52037218182"
 StochasticDiffEq = "789caeaf-c7a9-5a7d-9973-96adeb23e2a0"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 Zygote = "e88e6eb3-aa80-5325-afca-941959d7151f"
 
 [targets]
-test = ["Pkg", "SafeTestsets", "Test", "StaticArrays", "StochasticDiffEq", "Aqua", "Zygote"]
+test = ["Pkg", "PyCall", "SafeTestsets", "Test", "StaticArrays", "StochasticDiffEq", "Aqua", "Zygote"]

ext/PyCallExt.jl

@@ -0,0 +1,20 @@
+module PyCallExt
+
+using PyCall: PyCall, PyObject, PyAny, pyfunctionret, pyimport, hasproperty
+using SciMLBase: SciMLBase, solve
+
+# SciML uses a function's arity (number of arguments) to determine if it operates in place.
+# PyCall does not preserve arity, so we inspect Python functions to find their arity.
+function SciMLBase.numargs(f::PyObject)
+    inspect = pyimport("inspect")
+    f2 = hasproperty(f, :py_func) ? f.py_func : f
+    # if `f` is a bound method (i.e., `self.f`), `getfullargspec` includes
+    # `self` in the `args` list. So, we subtract 1 in that case:
+    length(first(inspect.getfullargspec(f2))) - inspect.ismethod(f2)
+end
+
+# differential equation solutions can be converted to lists, this tells PyCall not
+# to perform that conversion automatically when a solution is returned from `solve`
+PyCall.PyObject(::typeof(solve)) = pyfunctionret(solve, Any, Vararg{PyAny})
+
+end

test/python/Project.toml

@@ -0,0 +1,9 @@
+[deps]
+OrdinaryDiffEq = "1dea7af3-3e70-54e6-95c3-0bf5283fa5ed"
+PyCall = "438e738f-606a-5dbb-bf0a-cddfbfd45ab0"
+SciMLBase = "0bca4576-84f4-4d90-8ffe-ffa030f20462"
+
+[compat]
+OrdinaryDiffEq = "6.33"
+PyCall = "1.96"
+SciMLBase = "2"

test/python/pycall.jl

@@ -0,0 +1,45 @@
+using PyCall, SciMLBase, OrdinaryDiffEq
+
+py""" # This is a mess because normal site-packages is not writeable in CI
+import subprocess, sys, site
+subprocess.run([sys.executable, '-m', 'pip', 'install', '--user', 'julia'])
+sys.path.append(site.getusersitepackages())
+"""
+
+@testset "numargs" begin
+    py"""
+    def three_arg(a, b, c):
+        return a + b + c
+
+    def four_arg(a, b, c, d):
+        return a + b + c + d
+
+    class MyClass:
+        def three_arg_method(self, a, b, c):
+            return a + b + c
+
+        def four_arg_method(self, a, b, c, d):
+            return a + b + c + d
+    """
+
+    @test SciMLBase.numargs(py"three_arg") === 3
+    @test SciMLBase.numargs(py"four_arg") === 4
+    x = py"MyClass()"
+    @test SciMLBase.numargs(x.three_arg_method) === 3
+    @test SciMLBase.numargs(x.four_arg_method) === 4
+end
+
+@testset "solution handling" begin
+    py"""
+    from julia import OrdinaryDiffEq as ode
+
+    def f(u,p,t):
+        return -u
+
+    u0 = 0.5
+    tspan = (0., 1.)
+    prob = ode.ODEProblem(f, u0, tspan)
+    sol = ode.solve(prob, ode.Tsit5())
+    """
+    @test py"sol" isa ODESolution
+end

test/runtests.jl

@@ -15,6 +15,12 @@ function activate_downstream_env()
     Pkg.instantiate()
 end
 
+function activate_python_env()
+    Pkg.activate("python")
+    Pkg.develop(PackageSpec(path = dirname(@__DIR__)))
+    Pkg.instantiate()
+end
+
 @time begin
     if GROUP == "Core" || GROUP == "All"
         @time @safetestset "Aqua" begin
@@ -93,4 +99,11 @@ end
             include("downstream/remake_autodiff.jl")
         end
     end
+
+    if !is_APPVEYOR && GROUP == "Python"
+        activate_python_env()
+        @time @safetestset "PyCall" begin
+            include("python/pycall.jl")
+        end
+    end
 end