diff --git a/README.md b/README.md
index 344b8ed3..8e2d9c59 100644
--- a/README.md
+++ b/README.md
@@ -65,8 +65,8 @@ The `_demo` directory contains our demos (it start with `_` to prevent the `go`
 And the `py/_demo` directory contains python related demos:
 
 * [hellopy](py/_demo/hellopy/hello.go): link Python to Go and say `Hello world`
-* [clpy](py/_demo/clpy/cleval.go): compile Python code and eval.
-* [callpy](py/_demo/callpy/call.go): call Python standard library function `math.sqrt`.
+* [clpy](py/_demo/clpy/cleval.go): compile Python code and eval
+* [callpy](py/_demo/callpy/call.go): call Python standard library function `math.sqrt`
 
 ### How to run demos
 
diff --git a/_pydemo/callpy/callpy.go b/_pydemo/callpy/callpy.go
index 8900a9bb..21ec21ab 100644
--- a/_pydemo/callpy/callpy.go
+++ b/_pydemo/callpy/callpy.go
@@ -8,5 +8,5 @@ import (
 
 func main() {
 	x := math.Sqrt(py.Float(2))
-	c.Printf(c.Str("sqrt(2) = %f\n"), x.FloatAsDouble())
+	c.Printf(c.Str("sqrt(2) = %f\n"), x.Float64())
 }
diff --git a/cl/_testpy/callpy/in.go b/cl/_testpy/callpy/in.go
new file mode 100644
index 00000000..12424d62
--- /dev/null
+++ b/cl/_testpy/callpy/in.go
@@ -0,0 +1,15 @@
+package main
+
+import (
+	"github.com/goplus/llgo/c"
+	"github.com/goplus/llgo/py"
+	"github.com/goplus/llgo/py/math"
+	"github.com/goplus/llgo/py/os"
+)
+
+func main() {
+	x := math.Sqrt(py.Float(2))
+	wd := os.Getcwd()
+	c.Printf(c.Str("sqrt(2) = %f\n"), x.Float64())
+	c.Printf(c.Str("cwd = %s\n"), wd.CStr())
+}
diff --git a/cl/_testpy/callpy/out.ll b/cl/_testpy/callpy/out.ll
new file mode 100644
index 00000000..001dd685
--- /dev/null
+++ b/cl/_testpy/callpy/out.ll
@@ -0,0 +1,59 @@
+; ModuleID = 'main'
+source_filename = "main"
+
+@"main.init$guard" = global ptr null
+@__llgo_argc = global ptr null
+@__llgo_argv = global ptr null
+@sqrt = external global ptr
+@getcwd = external global ptr
+@0 = private unnamed_addr constant [14 x i8] c"sqrt(2) = %f\0A\00", align 1
+@1 = private unnamed_addr constant [10 x i8] c"cwd = %s\0A\00", align 1
+
+define void @main.init() {
+_llgo_0:
+  %0 = load i1, ptr @"main.init$guard", align 1
+  br i1 %0, label %_llgo_2, label %_llgo_1
+
+_llgo_1:                                          ; preds = %_llgo_0
+  store i1 true, ptr @"main.init$guard", align 1
+  call void @"github.com/goplus/llgo/py/math.init"()
+  call void @"github.com/goplus/llgo/py/os.init"()
+  br label %_llgo_2
+
+_llgo_2:                                          ; preds = %_llgo_1, %_llgo_0
+  ret void
+}
+
+define void @main(i32 %0, ptr %1) {
+_llgo_0:
+  store i32 %0, ptr @__llgo_argc, align 4
+  store ptr %1, ptr @__llgo_argv, align 8
+  call void @"github.com/goplus/llgo/internal/runtime.init"()
+  call void @main.init()
+  %2 = call ptr @PyFloat_FromDouble(double 2.000000e+00)
+  %3 = call ptr @PyObject_CallOneArg(ptr @sqrt, ptr %2)
+  %4 = call ptr @PyObject_CallNoArg(ptr @getcwd)
+  %5 = call double @PyFloat_AsDouble()
+  %6 = call i32 (ptr, ...) @printf(ptr @0, double %5)
+  %7 = call ptr @PyBytes_AsString()
+  %8 = call i32 (ptr, ...) @printf(ptr @1, ptr %7)
+  ret void
+}
+
+declare void @"github.com/goplus/llgo/py/math.init"()
+
+declare void @"github.com/goplus/llgo/py/os.init"()
+
+declare void @"github.com/goplus/llgo/internal/runtime.init"()
+
+declare ptr @PyFloat_FromDouble(double)
+
+declare ptr @PyObject_CallOneArg(ptr, ptr)
+
+declare ptr @PyObject_CallNoArg(ptr)
+
+declare double @PyFloat_AsDouble()
+
+declare i32 @printf(ptr, ...)
+
+declare ptr @PyBytes_AsString()
diff --git a/cl/_testpy/math/in.go b/cl/_testpy/math/in.go
new file mode 100644
index 00000000..5d6936f9
--- /dev/null
+++ b/cl/_testpy/math/in.go
@@ -0,0 +1,14 @@
+package math
+
+import (
+	_ "unsafe"
+
+	"github.com/goplus/llgo/py"
+)
+
+const (
+	LLGoPackage = "py.math"
+)
+
+//go:linkname Sqrt py.sqrt
+func Sqrt(x *py.Object) *py.Object
diff --git a/cl/_testpy/math/out.ll b/cl/_testpy/math/out.ll
new file mode 100644
index 00000000..f5feead3
--- /dev/null
+++ b/cl/_testpy/math/out.ll
@@ -0,0 +1,29 @@
+; ModuleID = 'math'
+source_filename = "math"
+
+@__llgo_py.math.sqrt = external global ptr
+@"math.init$guard" = global ptr null
+@__llgo_py.math = linkonce global ptr null
+@0 = private unnamed_addr constant [5 x i8] c"math\00", align 1
+
+define void @math.init() {
+_llgo_0:
+  %0 = load i1, ptr @"math.init$guard", align 1
+  br i1 %0, label %_llgo_2, label %_llgo_1
+
+_llgo_1:                                          ; preds = %_llgo_0
+  store i1 true, ptr @"math.init$guard", align 1
+  %1 = load ptr, ptr @__llgo_py.math, align 8
+  %2 = icmp ne ptr %1, null
+  br i1 %2, label %_llgo_2, label %_llgo_3
+
+_llgo_2:                                          ; preds = %_llgo_3, %_llgo_1, %_llgo_0
+  ret void
+
+_llgo_3:                                          ; preds = %_llgo_1
+  %3 = call ptr @PyImport_ImportModule(ptr @0)
+  store ptr %3, ptr @__llgo_py.math, align 8
+  br label %_llgo_2
+}
+
+declare ptr @PyImport_ImportModule(ptr)
diff --git a/cl/cltest/cltest.go b/cl/cltest/cltest.go
index 65816930..4b21cb04 100644
--- a/cl/cltest/cltest.go
+++ b/cl/cltest/cltest.go
@@ -147,6 +147,13 @@ func TestCompileEx(t *testing.T, src any, fname, expected string) {
 		}
 		return rt
 	})
+	prog.SetPython(func() *types.Package {
+		rt, err := imp.Import(llssa.PkgPython)
+		if err != nil {
+			t.Fatal("load python failed:", err)
+		}
+		return rt
+	})
 
 	ret, err := cl.NewPackage(prog, foo, files)
 	if err != nil {
diff --git a/cl/compile.go b/cl/compile.go
index 9f9bb2db..eddf4aea 100644
--- a/cl/compile.go
+++ b/cl/compile.go
@@ -143,6 +143,7 @@ type context struct {
 	goProg *ssa.Program
 	goTyps *types.Package
 	goPkg  *ssa.Package
+	pyMod  string
 	link   map[string]string           // pkgPath.nameInPkg => linkname
 	loaded map[*types.Package]*pkgInfo // loaded packages
 	bvals  map[ssa.Value]llssa.Expr    // block values
@@ -210,14 +211,19 @@ var (
 	argvTy = types.NewPointer(types.NewPointer(types.Typ[types.Int8]))
 )
 
-func (p *context) compileFuncDecl(pkg llssa.Package, f *ssa.Function) llssa.Function {
+func (p *context) compileFuncDecl(pkg llssa.Package, f *ssa.Function) (llssa.Function, llssa.PyFunction, int) {
 	pkgTypes, name, ftype := p.funcName(f, true)
 	if ftype != goFunc {
-		return nil
+		if ftype == pyFunc {
+			// TODO(xsw): pyMod == ""
+			fnName := pysymPrefix + p.pyMod + "." + name
+			return nil, pkg.NewPyFunc(fnName, f.Signature), pyFunc
+		}
+		return nil, nil, ignoredFunc
 	}
 	fn := pkg.FuncOf(name)
 	if fn != nil && fn.HasBody() {
-		return fn
+		return fn, nil, goFunc
 	}
 
 	var sig = f.Signature
@@ -244,6 +250,7 @@ func (p *context) compileFuncDecl(pkg llssa.Package, f *ssa.Function) llssa.Func
 	}
 	if nblk := len(f.Blocks); nblk > 0 {
 		fn.MakeBlocks(nblk) // to set fn.HasBody() = true
+		isPyMod := p.pyMod != ""
 		p.inits = append(p.inits, func() {
 			p.fn = fn
 			defer func() {
@@ -263,21 +270,29 @@ func (p *context) compileFuncDecl(pkg llssa.Package, f *ssa.Function) llssa.Func
 				off[i] = p.compilePhis(b, block)
 			}
 			for i, block := range f.Blocks {
-				p.compileBlock(b, block, off[i], i == 0 && name == "main")
+				doInit := (i == 0 && name == "main")
+				doPyModInit := (isPyMod && i == 1 && f.Name() == "init" && sig.Recv() == nil)
+				p.compileBlock(b, block, off[i], doInit, doPyModInit)
 			}
 			for _, phi := range p.phis {
 				phi()
 			}
 		})
 	}
-	return fn
+	return fn, nil, goFunc
 }
 
 // funcOf returns a function by name and set ftype = goFunc, cFunc, etc.
 // or returns nil and set ftype = llgoCstr, llgoAlloca, llgoUnreachable, etc.
-func (p *context) funcOf(fn *ssa.Function) (ret llssa.Function, ftype int) {
+func (p *context) funcOf(fn *ssa.Function) (aFn llssa.Function, pyFn llssa.PyFunction, ftype int) {
 	_, name, ftype := p.funcName(fn, false)
-	if ftype == llgoInstr {
+	switch ftype {
+	case pyFunc:
+		pkg := p.pkg
+		if pyFn = pkg.PyFuncOf(name); pyFn == nil {
+			pyFn = pkg.NewPyFunc(name, fn.Signature)
+		}
+	case llgoInstr:
 		switch name {
 		case "cstr":
 			ftype = llgoCstr
@@ -294,35 +309,60 @@ func (p *context) funcOf(fn *ssa.Function) (ret llssa.Function, ftype int) {
 		default:
 			panic("unknown llgo instruction: " + name)
 		}
-	} else {
+	default:
 		pkg := p.pkg
-		if ret = pkg.FuncOf(name); ret == nil && len(fn.FreeVars) == 0 {
+		if aFn = pkg.FuncOf(name); aFn == nil {
+			if len(fn.FreeVars) > 0 {
+				return nil, nil, ignoredFunc
+			}
 			sig := fn.Signature
-			ret = pkg.NewFuncEx(name, sig, llssa.Background(ftype), false)
+			aFn = pkg.NewFuncEx(name, sig, llssa.Background(ftype), false)
 		}
 	}
 	return
 }
 
-func (p *context) compileBlock(b llssa.Builder, block *ssa.BasicBlock, n int, doInit bool) llssa.BasicBlock {
-	ret := p.fn.Block(block.Index)
+func (p *context) compileBlock(b llssa.Builder, block *ssa.BasicBlock, n int, doInit, pyModInit bool) llssa.BasicBlock {
+	var last int
+	var instrs []ssa.Instruction
+	var ret = p.fn.Block(block.Index)
 	b.SetBlock(ret)
-	if doInit {
-		prog := p.prog
-		pkg := p.pkg
-		fn := p.fn
-		argc := pkg.NewVar("__llgo_argc", types.NewPointer(types.Typ[types.Int32]), llssa.InC)
-		argv := pkg.NewVar("__llgo_argv", types.NewPointer(argvTy), llssa.InC)
-		argc.Init(prog.Null(argc.Type))
-		argv.Init(prog.Null(argv.Type))
-		b.Store(argc.Expr, fn.Param(0))
-		b.Store(argv.Expr, fn.Param(1))
-		callRuntimeInit(b, pkg)
-		b.Call(pkg.FuncOf("main.init").Expr)
+	if pyModInit {
+		last = len(block.Instrs) - 1
+		instrs = block.Instrs[n:last]
+	} else {
+		instrs = block.Instrs[n:]
+		if doInit {
+			prog := p.prog
+			pkg := p.pkg
+			fn := p.fn
+			argc := pkg.NewVar("__llgo_argc", types.NewPointer(types.Typ[types.Int32]), llssa.InC)
+			argv := pkg.NewVar("__llgo_argv", types.NewPointer(argvTy), llssa.InC)
+			argc.Init(prog.Null(argc.Type))
+			argv.Init(prog.Null(argv.Type))
+			b.Store(argc.Expr, fn.Param(0))
+			b.Store(argv.Expr, fn.Param(1))
+			callRuntimeInit(b, pkg)
+			b.Call(pkg.FuncOf("main.init").Expr)
+		}
 	}
-	for _, instr := range block.Instrs[n:] {
+	for _, instr := range instrs {
 		p.compileInstr(b, instr)
 	}
+	if pyModInit {
+		jump := block.Instrs[last].(*ssa.Jump)
+		jumpTo := p.jumpTo(jump)
+		modPath := p.pyMod
+		modName := pysymPrefix + modPath
+		modPtr := p.pkg.NewPyModVar(modName).Expr
+		mod := b.Load(modPtr)
+		cond := b.BinOp(token.NEQ, mod, b.Prog.Null(mod.Type))
+		newBlk := p.fn.MakeBlock()
+		b.If(cond, jumpTo, newBlk)
+		b.SetBlock(newBlk)
+		b.Store(modPtr, b.ImportPyMod(modPath))
+		b.Jump(jumpTo)
+	}
 	return ret
 }
 
@@ -507,11 +547,14 @@ func (p *context) compileInstrOrValue(b llssa.Builder, iv instrOrValue, asValue
 				ret = b.BuiltinCall(fn, args...)
 			}
 		case *ssa.Function:
-			fn, ftype := p.compileFunction(cv)
+			aFn, pyFn, ftype := p.compileFunction(cv)
 			switch ftype {
 			case goFunc, cFunc:
 				args := p.compileValues(b, args, kind)
-				ret = b.Call(fn.Expr, args...)
+				ret = b.Call(aFn.Expr, args...)
+			case pyFunc:
+				args := p.compileValues(b, args, kind)
+				ret = b.Call(pyFn.Expr, args...)
 			case llgoCstr:
 				ret = cstr(b, args)
 			case llgoAdvance:
@@ -643,6 +686,12 @@ func (p *context) compileInstrOrValue(b llssa.Builder, iv instrOrValue, asValue
 	return ret
 }
 
+func (p *context) jumpTo(v *ssa.Jump) llssa.BasicBlock {
+	fn := p.fn
+	succs := v.Block().Succs
+	return fn.Block(succs[0].Index)
+}
+
 func (p *context) compileInstr(b llssa.Builder, instr ssa.Instruction) {
 	if iv, ok := instr.(instrOrValue); ok {
 		p.compileInstrOrValue(b, iv, false)
@@ -666,9 +715,7 @@ func (p *context) compileInstr(b llssa.Builder, instr ssa.Instruction) {
 		val := p.compileValue(b, v.Val)
 		b.Store(ptr, val)
 	case *ssa.Jump:
-		fn := p.fn
-		succs := v.Block().Succs
-		jmpb := fn.Block(succs[0].Index)
+		jmpb := p.jumpTo(v)
 		b.Jump(jmpb)
 	case *ssa.Return:
 		var results []llssa.Expr
@@ -699,12 +746,13 @@ func (p *context) compileInstr(b llssa.Builder, instr ssa.Instruction) {
 	}
 }
 
-func (p *context) compileFunction(v *ssa.Function) (llssa.Function, int) {
+func (p *context) compileFunction(v *ssa.Function) (goFn llssa.Function, pyFn llssa.PyFunction, kind int) {
 	// v.Pkg == nil: means auto generated function?
 	if v.Pkg == p.goPkg || v.Pkg == nil {
 		// function in this package
-		if fn := p.compileFuncDecl(p.pkg, v); fn != nil {
-			return fn, goFunc
+		goFn, pyFn, kind = p.compileFuncDecl(p.pkg, v)
+		if kind != ignoredFunc {
+			return
 		}
 	}
 	return p.funcOf(v)
@@ -723,8 +771,11 @@ func (p *context) compileValue(b llssa.Builder, v ssa.Value) llssa.Expr {
 			}
 		}
 	case *ssa.Function:
-		fn, _ := p.compileFunction(v)
-		return fn.Expr
+		aFn, pyFn, _ := p.compileFunction(v)
+		if aFn != nil {
+			return aFn.Expr
+		}
+		return pyFn.Expr
 	case *ssa.Global:
 		g := p.varOf(v)
 		return g.Expr
@@ -807,6 +858,7 @@ func NewPackage(prog llssa.Program, pkg *ssa.Package, files []*ast.File) (ret ll
 			types.Unsafe: {kind: PkgDeclOnly}, // TODO(xsw): PkgNoInit or PkgDeclOnly?
 		},
 	}
+	ctx.initPyModule()
 	ctx.initFiles(pkgPath, files)
 	for _, m := range members {
 		member := m.val
diff --git a/cl/compile_test.go b/cl/compile_test.go
index 76be7e7a..1af95938 100644
--- a/cl/compile_test.go
+++ b/cl/compile_test.go
@@ -28,6 +28,10 @@ func testCompile(t *testing.T, src, expected string) {
 	cltest.TestCompileEx(t, src, "foo.go", expected)
 }
 
+func TestFromTestpy(t *testing.T) {
+	cltest.FromDir(t, "", "./_testpy", false)
+}
+
 func TestFromTestlibc(t *testing.T) {
 	cltest.FromDir(t, "", "./_testlibc", false)
 }
diff --git a/cl/import.go b/cl/import.go
index dde42752..4f42f2c3 100644
--- a/cl/import.go
+++ b/cl/import.go
@@ -30,6 +30,8 @@ import (
 	"golang.org/x/tools/go/ssa"
 )
 
+// -----------------------------------------------------------------------------
+
 type symInfo struct {
 	file     string
 	fullName string
@@ -305,6 +307,7 @@ const (
 	ignoredFunc = iota
 	goFunc      = int(llssa.InGo)
 	cFunc       = int(llssa.InC)
+	pyFunc      = int(llssa.InPython)
 	llgoInstr   = -1
 
 	llgoInstrBase   = 0x80
@@ -339,6 +342,9 @@ func (p *context) funcName(fn *ssa.Function, ignore bool) (*types.Package, strin
 		if strings.HasPrefix(v, "C.") {
 			return nil, v[2:], cFunc
 		}
+		if strings.HasPrefix(v, "py.") {
+			return pkg, v[3:], pyFunc
+		}
 		if strings.HasPrefix(v, "llgo.") {
 			return nil, v[5:], llgoInstr
 		}
@@ -391,3 +397,17 @@ func pkgKindByPath(pkgPath string) int {
 	}
 	return PkgNormal
 }
+
+// -----------------------------------------------------------------------------
+
+const (
+	pysymPrefix = "__llgo_py."
+)
+
+func (p *context) initPyModule() {
+	if kind, mod := pkgKindByScope(p.goTyps.Scope()); kind == PkgPyModule {
+		p.pyMod = mod
+	}
+}
+
+// -----------------------------------------------------------------------------
diff --git a/internal/build/build.go b/internal/build/build.go
index 9a7644d8..2e18e97f 100644
--- a/internal/build/build.go
+++ b/internal/build/build.go
@@ -120,18 +120,31 @@ func Do(args []string, conf *Config) {
 		cl.SetDebug(cl.DbgFlagAll)
 	}
 
+	var needRt bool
 	var rt []*packages.Package
 	prog := llssa.NewProgram(nil)
+	load := func() []*packages.Package {
+		if rt == nil {
+			var err error
+			rt, err = packages.Load(cfg, llssa.PkgRuntime, llssa.PkgPython)
+			check(err)
+		}
+		return rt
+	}
 	prog.SetRuntime(func() *types.Package {
-		rt, err = packages.Load(cfg, llssa.PkgRuntime)
-		check(err)
+		needRt = true
+		rt := load()
 		return rt[0].Types
 	})
+	prog.SetPython(func() *types.Package {
+		rt := load()
+		return rt[1].Types
+	})
 
 	pkgs := buildAllPkgs(prog, initial, mode, verbose)
 
 	var runtimeFiles []string
-	if rt != nil {
+	if needRt {
 		runtimeFiles = allLinkFiles(rt)
 	}
 	if mode != ModeBuild {
diff --git a/internal/llgen/llgen.go b/internal/llgen/llgen.go
index fafcb959..a9e70e63 100644
--- a/internal/llgen/llgen.go
+++ b/internal/llgen/llgen.go
@@ -30,6 +30,7 @@ import (
 	"golang.org/x/tools/go/ssa/ssautil"
 
 	llssa "github.com/goplus/llgo/ssa"
+	cpackages "golang.org/x/tools/go/packages"
 )
 
 func Init() {
@@ -71,11 +72,10 @@ func Gen(pkgPath, inFile string, src any) string {
 	}
 
 	prog := llssa.NewProgram(nil)
-	prog.SetRuntime(func() *types.Package {
-		rt, err := imp.Import(llssa.PkgRuntime)
-		check(err)
-		return rt
+	initRtAndPy(prog, &cpackages.Config{
+		Mode: loadSyntax | cpackages.NeedDeps,
 	})
+
 	ret, err := cl.NewPackage(prog, ssaPkg, files)
 	check(err)
 
diff --git a/internal/llgen/llgenf.go b/internal/llgen/llgenf.go
index 985ceaec..b7eeddaf 100644
--- a/internal/llgen/llgenf.go
+++ b/internal/llgen/llgenf.go
@@ -38,6 +38,27 @@ const (
 	loadSyntax  = loadTypes | packages.NeedSyntax | packages.NeedTypesInfo
 )
 
+func initRtAndPy(prog llssa.Program, cfg *packages.Config) {
+	var pkgRtAndPy []*packages.Package
+	load := func() []*packages.Package {
+		if pkgRtAndPy == nil {
+			var err error
+			pkgRtAndPy, err = packages.Load(cfg, llssa.PkgRuntime, llssa.PkgPython)
+			check(err)
+		}
+		return pkgRtAndPy
+	}
+
+	prog.SetRuntime(func() *types.Package {
+		rt := load()
+		return rt[0].Types
+	})
+	prog.SetPython(func() *types.Package {
+		rt := load()
+		return rt[1].Types
+	})
+}
+
 func GenFrom(fileOrPkg string) string {
 	cfg := &packages.Config{
 		Mode: loadSyntax | packages.NeedDeps,
@@ -52,11 +73,7 @@ func GenFrom(fileOrPkg string) string {
 	ssaPkg.Build()
 
 	prog := llssa.NewProgram(nil)
-	prog.SetRuntime(func() *types.Package {
-		rt, err := packages.Load(cfg, llssa.PkgRuntime)
-		check(err)
-		return rt[0].Types
-	})
+	initRtAndPy(prog, cfg)
 
 	if Verbose {
 		ssaPkg.WriteTo(os.Stderr)
diff --git a/internal/pyimport/llgo_autogen.lla b/internal/pyimport/llgo_autogen.lla
deleted file mode 100644
index d839012f..00000000
Binary files a/internal/pyimport/llgo_autogen.lla and /dev/null differ
diff --git a/internal/pyimport/pyimport.go b/internal/pyimport/pyimport.go
index 69f96fad..72c23de7 100644
--- a/internal/pyimport/pyimport.go
+++ b/internal/pyimport/pyimport.go
@@ -23,10 +23,16 @@ import (
 	"github.com/goplus/llgo/py"
 )
 
+const (
+	LLGoPackage = "decl"
+)
+
+/*
 func init() {
 	py.Initialize()
 	py.SetProgramName(*c.Argv)
 }
+*/
 
 //go:linkname Module C.PyImport_ImportModule
 func Module(name *c.Char) *py.Module
diff --git a/py/_demo/callpy/call.go b/py/_demo/callpy/call.go
index 58904c9c..0198b8c4 100644
--- a/py/_demo/callpy/call.go
+++ b/py/_demo/callpy/call.go
@@ -11,7 +11,7 @@ func main() {
 	math := py.ImportModule(c.Str("math"))
 	sqrt := math.GetAttrString(c.Str("sqrt"))
 	sqrt2 := sqrt.CallOneArg(py.Float(2))
-	c.Printf(c.Str("sqrt(2) = %f\n"), sqrt2.FloatAsDouble())
+	c.Printf(c.Str("sqrt(2) = %f\n"), sqrt2.Float64())
 	sqrt2.DecRef()
 	sqrt.DecRef()
 	math.DecRef()
diff --git a/py/bytes.go b/py/bytes.go
new file mode 100644
index 00000000..cd6e257a
--- /dev/null
+++ b/py/bytes.go
@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2024 The GoPlus Authors (goplus.org). All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package py
+
+import (
+	_ "unsafe"
+
+	"github.com/goplus/llgo/c"
+)
+
+// https://docs.python.org/3/c-api/bytes.html
+
+// String returns a new bytes object from a C string.
+//
+//go:linkname StringFrom C.PyBytes_FromString
+func StringFrom(s *c.Char) *Object
+
+//go:linkname stringFromStringAndSize C.PyBytes_FromStringAndSize
+func stringFromStringAndSize(s *c.Char, size uintptr) *Object
+
+// String returns a new bytes object from a Go string.
+func String(s string) *Object {
+	return stringFromStringAndSize(c.GoStringData(s), uintptr(len(s)))
+}
+
+// CStr returns the content of a bytes object as a C string.
+//
+// llgo:link (*Object).CStr C.PyBytes_AsString
+func (o *Object) CStr() *c.Char { return nil }
+
+// llgo:link (*Object).Strlen C.PyBytes_Size
+func (o *Object) Strlen() uintptr { return 0 }
diff --git a/py/float.go b/py/float.go
index a4916225..1cfa7a38 100644
--- a/py/float.go
+++ b/py/float.go
@@ -28,5 +28,5 @@ func Float(v float64) *Object
 //go:linkname FloatFromSring C.PyFloat_FromString
 func FloatFromSring(v *Object) *Object
 
-// llgo:link (*Object).FloatAsDouble C.PyFloat_AsDouble
-func (o *Object) FloatAsDouble() float64 { panic("unreachable") }
+// llgo:link (*Object).Float64 C.PyFloat_AsDouble
+func (o *Object) Float64() float64 { return 0 }
diff --git a/py/module.go b/py/module.go
index 64c1a8a8..8dddecbf 100644
--- a/py/module.go
+++ b/py/module.go
@@ -53,6 +53,6 @@ func Import(name *Object) *Module
 // manipulate a module’s __dict__.
 //
 // llgo:link (*Module).GetDict C.PyModule_GetDict
-func (m *Module) GetDict() *Object { panic("unreachable") }
+func (m *Module) GetDict() *Object { return nil }
 
 // -----------------------------------------------------------------------------
diff --git a/py/object.go b/py/object.go
index 35c798e8..cb973653 100644
--- a/py/object.go
+++ b/py/object.go
@@ -36,7 +36,7 @@ type Object struct {
 func BuildValue(format *c.Char, __llgo_va_list ...any) *Object
 
 // llgo:link (*Object).DecRef C.Py_DecRef
-func (o *Object) DecRef() { panic("unreachable") }
+func (o *Object) DecRef() {}
 
 // -----------------------------------------------------------------------------
 
@@ -44,10 +44,10 @@ func (o *Object) DecRef() { panic("unreachable") }
 // or nil on failure. This is the equivalent of the Python expression o.attrName.
 //
 // llgo:link (*Object).GetAttr C.PyObject_GetAttr
-func (o *Object) GetAttr(attrName *Object) *Object { panic("unreachable") }
+func (o *Object) GetAttr(attrName *Object) *Object { return nil }
 
 // llgo:link (*Object).GetAttrString C.PyObject_GetAttrString
-func (o *Object) GetAttrString(attrName *c.Char) *Object { panic("unreachable") }
+func (o *Object) GetAttrString(attrName *c.Char) *Object { return nil }
 
 // -----------------------------------------------------------------------------
 
@@ -55,7 +55,7 @@ func (o *Object) GetAttrString(attrName *c.Char) *Object { panic("unreachable")
 // 0 otherwise. This function always succeeds.
 //
 // llgo:link (*Object).Callable C.PyCallable_Check
-func (o *Object) Callable() int { panic("unreachable") }
+func (o *Object) Callable() c.Int { return 0 }
 
 // Call a callable Python object o, with arguments given by the tuple args, and
 // named arguments given by the dictionary kwargs.
@@ -69,7 +69,7 @@ func (o *Object) Callable() int { panic("unreachable") }
 // This is the equivalent of the Python expression: o(*args, **kwargs).
 //
 // llgo:link (*Object).Call C.PyObject_Call
-func (o *Object) Call(args, kwargs *Object) *Object { panic("unreachable") }
+func (o *Object) Call(args, kwargs *Object) *Object { return nil }
 
 // Call a callable Python object callable without any arguments. It is the most
 // efficient way to call a callable Python object without any argument.
@@ -78,7 +78,7 @@ func (o *Object) Call(args, kwargs *Object) *Object { panic("unreachable") }
 // on failure.
 //
 // llgo:link (*Object).CallNoArgs C.PyObject_CallNoArgs
-func (o *Object) CallNoArgs() *Object { panic("unreachable") }
+func (o *Object) CallNoArgs() *Object { return nil }
 
 // Call a callable Python object callable with exactly 1 positional argument arg
 // and no keyword arguments.
@@ -87,7 +87,7 @@ func (o *Object) CallNoArgs() *Object { panic("unreachable") }
 // on failure.
 //
 // llgo:link (*Object).CallOneArg C.PyObject_CallOneArg
-func (o *Object) CallOneArg(arg *Object) *Object { panic("unreachable") }
+func (o *Object) CallOneArg(arg *Object) *Object { return nil }
 
 // Call a callable Python object o, with arguments given by the tuple args. If no
 // arguments are needed, then args can be nil.
@@ -98,7 +98,7 @@ func (o *Object) CallOneArg(arg *Object) *Object { panic("unreachable") }
 // This is the equivalent of the Python expression: o(*args).
 //
 // llgo:link (*Object).CallObject C.PyObject_CallObject
-func (o *Object) CallObject(callable, args *Object) *Object { panic("unreachable") }
+func (o *Object) CallObject(callable, args *Object) *Object { return nil }
 
 // Call a callable Python object o, with a variable number of C arguments. The C
 // arguments are described using a py.BuildValue style format string. The format
@@ -113,7 +113,7 @@ func (o *Object) CallObject(callable, args *Object) *Object { panic("unreachable
 // faster alternative.
 //
 // llgo:link (*Object).CallFunction C.PyObject_CallFunction
-func (o *Object) CallFunction(format *c.Char, __llgo_va_list ...any) *Object { panic("unreachable") }
+func (o *Object) CallFunction(format *c.Char, __llgo_va_list ...any) *Object { return nil }
 
 // Call a callable Python object o, with a variable number of PyObject* arguments.
 // The arguments are provided as a variable number of parameters followed by nil.
@@ -124,7 +124,7 @@ func (o *Object) CallFunction(format *c.Char, __llgo_va_list ...any) *Object { p
 // This is the equivalent of the Python expression: o(arg1, arg2, ...).
 //
 // llgo:link (*Object).CallFunctionObjArgs C.PyObject_CallFunctionObjArgs
-func (o *Object) CallFunctionObjArgs(__llgo_va_list ...any) *Object { panic("unreachable") }
+func (o *Object) CallFunctionObjArgs(__llgo_va_list ...any) *Object { return nil }
 
 // llgo:link (*Object).CallMethod C.PyObject_CallMethod
 func (o *Object) CallMethod(name *c.Char, format *c.Char, __llgo_va_list ...any) *Object {
@@ -132,27 +132,27 @@ func (o *Object) CallMethod(name *c.Char, format *c.Char, __llgo_va_list ...any)
 }
 
 // llgo:link (*Object).CallMethodObjArgs C.PyObject_CallMethodObjArgs
-func (o *Object) CallMethodObjArgs(name *Object, __llgo_va_list ...any) *Object { panic("unreachable") }
+func (o *Object) CallMethodObjArgs(name *Object, __llgo_va_list ...any) *Object { return nil }
 
 // llgo:link (*Object).CallMethodNoArgs C.PyObject_CallMethodNoArgs
-func (o *Object) CallMethodNoArgs(name *Object) *Object { panic("unreachable") }
+func (o *Object) CallMethodNoArgs(name *Object) *Object { return nil }
 
 // llgo:link (*Object).CallMethodOneArg C.PyObject_CallMethodOneArg
-func (o *Object) CallMethodOneArg(name, arg *Object) *Object { panic("unreachable") }
+func (o *Object) CallMethodOneArg(name, arg *Object) *Object { return nil }
 
 // llgo:link (*Object).Vectorcall C.PyObject_Vectorcall
 func (o *Object) Vectorcall(args **Object, nargs uintptr, kwnames *Object) *Object {
-	panic("unreachable")
+	return nil
 }
 
 // llgo:link (*Object).VectorcallDict C.PyObject_VectorcallDict
 func (o *Object) VectorcallDict(args **Object, nargs uintptr, kwdict *Object) *Object {
-	panic("unreachable")
+	return nil
 }
 
 // llgo:link (*Object).VectorcallMethod C.PyObject_VectorcallMethod
 func (o *Object) VectorcallMethod(name *Object, args **Object, nargs uintptr, kwnames *Object) *Object {
-	panic("unreachable")
+	return nil
 }
 
 // -----------------------------------------------------------------------------
diff --git a/py/os/os.go b/py/os/os.go
new file mode 100644
index 00000000..8a421dac
--- /dev/null
+++ b/py/os/os.go
@@ -0,0 +1,30 @@
+/*
+ * Copyright (c) 2024 The GoPlus Authors (goplus.org). All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package os
+
+import (
+	_ "unsafe"
+
+	"github.com/goplus/llgo/py"
+)
+
+const (
+	LLGoPackage = "py.os"
+)
+
+//go:linkname Getcwd py.getcwd
+func Getcwd() *py.Object
diff --git a/ssa/cl_test.go b/ssa/cl_test.go
index 0a9d8493..4d79ec49 100644
--- a/ssa/cl_test.go
+++ b/ssa/cl_test.go
@@ -22,6 +22,10 @@ import (
 	"github.com/goplus/llgo/cl/cltest"
 )
 
+func TestFromTestpy(t *testing.T) {
+	cltest.FromDir(t, "", "../cl/_testpy", false)
+}
+
 func TestFromTestrt(t *testing.T) {
 	cltest.FromDir(t, "", "../cl/_testrt", true)
 }
diff --git a/ssa/decl.go b/ssa/decl.go
index af4603b2..b89243fa 100644
--- a/ssa/decl.go
+++ b/ssa/decl.go
@@ -18,6 +18,7 @@ package ssa
 
 import (
 	"go/types"
+	"log"
 	"strconv"
 
 	"github.com/goplus/llvm"
@@ -68,6 +69,23 @@ type aGlobal struct {
 // variable.
 type Global = *aGlobal
 
+// NewVar creates a new global variable.
+func (p Package) NewVar(name string, typ types.Type, bg Background) Global {
+	if v, ok := p.vars[name]; ok {
+		return v
+	}
+	t := p.Prog.Type(typ, bg)
+	gbl := llvm.AddGlobal(p.mod, t.ll, name)
+	ret := &aGlobal{Expr{gbl, t}}
+	p.vars[name] = ret
+	return ret
+}
+
+// VarOf returns a global variable by name.
+func (p Package) VarOf(name string) Global {
+	return p.vars[name]
+}
+
 // Init initializes the global variable with the given value.
 func (g Global) Init(v Expr) {
 	g.impl.SetInitializer(v.impl)
@@ -140,6 +158,31 @@ type aFunction struct {
 // Function represents a function or method.
 type Function = *aFunction
 
+// NewFunc creates a new function.
+func (p Package) NewFunc(name string, sig *types.Signature, bg Background) Function {
+	return p.NewFuncEx(name, sig, bg, false)
+}
+
+// NewFuncEx creates a new function.
+func (p Package) NewFuncEx(name string, sig *types.Signature, bg Background, hasFreeVars bool) Function {
+	if v, ok := p.fns[name]; ok {
+		return v
+	}
+	t := p.Prog.FuncDecl(sig, bg)
+	if debugInstr {
+		log.Println("NewFunc", name, t.raw.Type, "hasFreeVars:", hasFreeVars)
+	}
+	fn := llvm.AddFunction(p.mod, name, t.ll)
+	ret := newFunction(fn, t, p, p.Prog, hasFreeVars)
+	p.fns[name] = ret
+	return ret
+}
+
+// FuncOf returns a function by name.
+func (p Package) FuncOf(name string) Function {
+	return p.fns[name]
+}
+
 func newFunction(fn llvm.Value, t Type, pkg Package, prog Program, hasFreeVars bool) Function {
 	params, hasVArg := newParams(t, prog)
 	base := 0
@@ -212,22 +255,60 @@ func (p Function) MakeBody(nblk int) Builder {
 
 // MakeBlocks creates nblk basic blocks for the function.
 func (p Function) MakeBlocks(nblk int) []BasicBlock {
-	if p.blks == nil {
+	n := len(p.blks)
+	if n == 0 {
 		p.blks = make([]BasicBlock, 0, nblk)
 	}
-	n := len(p.blks)
-	f := p.impl
 	for i := 0; i < nblk; i++ {
-		label := "_llgo_" + strconv.Itoa(i)
-		blk := llvm.AddBasicBlock(f, label)
-		p.blks = append(p.blks, &aBasicBlock{blk, p, n + i})
+		p.addBlock(n + i)
 	}
 	return p.blks[n:]
 }
 
+func (p Function) addBlock(idx int) BasicBlock {
+	label := "_llgo_" + strconv.Itoa(idx)
+	blk := llvm.AddBasicBlock(p.impl, label)
+	ret := &aBasicBlock{blk, p, idx}
+	p.blks = append(p.blks, ret)
+	return ret
+}
+
+// MakeBlock creates a new basic block for the function.
+func (p Function) MakeBlock() BasicBlock {
+	return p.addBlock(len(p.blks))
+}
+
 // Block returns the ith basic block of the function.
 func (p Function) Block(idx int) BasicBlock {
 	return p.blks[idx]
 }
 
 // -----------------------------------------------------------------------------
+
+type aPyFunction struct {
+	Expr
+	Obj Global
+}
+
+// PyFunction represents a python function.
+type PyFunction = *aPyFunction
+
+// NewPyFunc creates a new python function.
+func (p Package) NewPyFunc(name string, sig *types.Signature) PyFunction {
+	if v, ok := p.pyfns[name]; ok {
+		return v
+	}
+	obj := p.NewVar(name, p.Prog.PyObjectPtrPtr().RawType(), InC)
+	ty := &aType{obj.ll, rawType{sig}, vkPyFunc}
+	expr := Expr{obj.impl, ty}
+	ret := &aPyFunction{expr, obj}
+	p.pyfns[name] = ret
+	return ret
+}
+
+// PyFuncOf returns a function by name.
+func (p Package) PyFuncOf(name string) PyFunction {
+	return p.pyfns[name]
+}
+
+// -----------------------------------------------------------------------------
diff --git a/ssa/expr.go b/ssa/expr.go
index 193b8f49..5b4801eb 100644
--- a/ssa/expr.go
+++ b/ssa/expr.go
@@ -1204,7 +1204,6 @@ func (b Builder) InlineCall(fn Expr, args ...Expr) (ret Expr) {
 //	t4 = t3()
 //	t7 = invoke t5.Println(...t6)
 func (b Builder) Call(fn Expr, args ...Expr) (ret Expr) {
-	prog := b.Prog
 	if debugInstr {
 		var b bytes.Buffer
 		name := fn.impl.Name()
@@ -1219,11 +1218,16 @@ func (b Builder) Call(fn Expr, args ...Expr) (ret Expr) {
 		}
 		log.Println(b.String())
 	}
+	var kind = fn.kind
+	if kind == vkPyFunc {
+		return b.pyCall(fn, args)
+	}
 	var ll llvm.Type
 	var data Expr
 	var sig *types.Signature
+	var prog = b.Prog
 	var raw = fn.raw.Type
-	switch fn.kind {
+	switch kind {
 	case vkClosure:
 		data = b.Field(fn, 1)
 		fn = b.Field(fn, 0)
diff --git a/ssa/package.go b/ssa/package.go
index 1ee6b8cf..b0fbb0e0 100644
--- a/ssa/package.go
+++ b/ssa/package.go
@@ -19,13 +19,13 @@ package ssa
 import (
 	"go/token"
 	"go/types"
-	"log"
 
 	"github.com/goplus/llvm"
 	"golang.org/x/tools/go/types/typeutil"
 )
 
 const (
+	PkgPython  = "github.com/goplus/llgo/py"
 	PkgRuntime = "github.com/goplus/llgo/internal/runtime"
 )
 
@@ -103,6 +103,9 @@ type aProgram struct {
 	rt    *types.Package
 	rtget func() *types.Package
 
+	py    *types.Package
+	pyget func() *types.Package
+
 	target *Target
 	td     llvm.TargetData
 	// tm  llvm.TargetMachine
@@ -131,8 +134,15 @@ type aProgram struct {
 	uintptrTy Type
 	intTy     Type
 	f64Ty     Type
+	pyObjPtr  Type
+	pyObjPPtr Type
+
+	pyImpTy    *types.Signature
+	callNoArg  *types.Signature
+	callOneArg *types.Signature
 
 	needRuntime bool
+	needPyInit  bool
 }
 
 // A Program presents a program.
@@ -158,6 +168,17 @@ func NewProgram(target *Target) Program {
 	return &aProgram{ctx: ctx, gocvt: newGoTypes(), target: target, td: td, named: make(map[string]llvm.Type)}
 }
 
+// SetPython sets the Python package.
+// Its type can be *types.Package or func() *types.Package.
+func (p Program) SetPython(py any) {
+	switch v := py.(type) {
+	case *types.Package:
+		p.py = v
+	case func() *types.Package:
+		p.pyget = v
+	}
+}
+
 // SetRuntime sets the runtime.
 // Its type can be *types.Package or func() *types.Package.
 func (p Program) SetRuntime(runtime any) {
@@ -182,12 +203,25 @@ func (p Program) runtime() *types.Package {
 	return p.rt
 }
 
+func (p Program) python() *types.Package {
+	if p.py == nil {
+		p.py = p.pyget()
+	}
+	return p.py
+}
+
 func (p Program) rtNamed(name string) *types.Named {
 	t := p.runtime().Scope().Lookup(name).Type().(*types.Named)
 	t, _ = p.gocvt.cvtNamed(t)
 	return t
 }
 
+func (p Program) pyNamed(name string) *types.Named {
+	// TODO(xsw): does python type need to convert?
+	t := p.python().Scope().Lookup(name).Type().(*types.Named)
+	return t
+}
+
 func (p Program) rtType(name string) Type {
 	return p.rawType(p.rtNamed(name))
 }
@@ -228,8 +262,26 @@ func (p Program) NewPackage(name, pkgPath string) Package {
 	gbls := make(map[string]Global)
 	fns := make(map[string]Function)
 	stubs := make(map[string]Function)
+	pyfns := make(map[string]PyFunction)
 	p.needRuntime = false
-	return &aPackage{mod, gbls, fns, stubs, p}
+	return &aPackage{mod, gbls, fns, stubs, pyfns, p}
+}
+
+// PyObjectPtrPtr returns the **py.Object type.
+func (p Program) PyObjectPtrPtr() Type {
+	if p.pyObjPPtr == nil {
+		p.pyObjPPtr = p.Pointer(p.PyObjectPtr())
+	}
+	return p.pyObjPPtr
+}
+
+// PyObjectPtr returns the *py.Object type.
+func (p Program) PyObjectPtr() Type {
+	if p.pyObjPtr == nil {
+		objPtr := types.NewPointer(p.pyNamed("Object"))
+		p.pyObjPtr = p.rawType(objPtr)
+	}
+	return p.pyObjPtr
 }
 
 // Void returns void type.
@@ -316,6 +368,7 @@ type aPackage struct {
 	vars  map[string]Global
 	fns   map[string]Function
 	stubs map[string]Function
+	pyfns map[string]PyFunction
 	Prog  Program
 }
 
@@ -328,40 +381,6 @@ func (p Package) NewConst(name string, val constant.Value) NamedConst {
 }
 */
 
-// NewVar creates a new global variable.
-func (p Package) NewVar(name string, typ types.Type, bg Background) Global {
-	t := p.Prog.Type(typ, bg)
-	gbl := llvm.AddGlobal(p.mod, t.ll, name)
-	ret := &aGlobal{Expr{gbl, t}}
-	p.vars[name] = ret
-	return ret
-}
-
-// VarOf returns a global variable by name.
-func (p Package) VarOf(name string) Global {
-	return p.vars[name]
-}
-
-// NewFunc creates a new function.
-func (p Package) NewFunc(name string, sig *types.Signature, bg Background) Function {
-	return p.NewFuncEx(name, sig, bg, false)
-}
-
-// NewFuncEx creates a new function.
-func (p Package) NewFuncEx(name string, sig *types.Signature, bg Background, hasFreeVars bool) Function {
-	if v, ok := p.fns[name]; ok {
-		return v
-	}
-	t := p.Prog.FuncDecl(sig, bg)
-	if debugInstr {
-		log.Println("NewFunc", name, t.raw.Type, "hasFreeVars:", hasFreeVars)
-	}
-	fn := llvm.AddFunction(p.mod, name, t.ll)
-	ret := newFunction(fn, t, p, p.Prog, hasFreeVars)
-	p.fns[name] = ret
-	return ret
-}
-
 func (p Package) rtFunc(fnName string) Expr {
 	fn := p.Prog.runtime().Scope().Lookup(fnName).(*types.Func)
 	name := FullName(fn.Pkg(), fnName)
@@ -369,6 +388,11 @@ func (p Package) rtFunc(fnName string) Expr {
 	return p.NewFunc(name, sig, InGo).Expr
 }
 
+func (p Package) pyFunc(fullName string, sig *types.Signature) Expr {
+	p.Prog.needPyInit = true
+	return p.NewFunc(fullName, sig, InC).Expr
+}
+
 func (p Package) closureStub(b Builder, t *types.Struct, v Expr) Expr {
 	name := v.impl.Name()
 	prog := b.Prog
@@ -402,11 +426,6 @@ func (p Package) closureStub(b Builder, t *types.Struct, v Expr) Expr {
 	return b.aggregateValue(prog.rawType(t), v.impl, nilVal)
 }
 
-// FuncOf returns a function by name.
-func (p Package) FuncOf(name string) Function {
-	return p.fns[name]
-}
-
 // -----------------------------------------------------------------------------
 
 // String returns a string representation of the package.
@@ -455,3 +474,73 @@ func (p *Package) WriteFile(file string) (err error) {
 */
 
 // -----------------------------------------------------------------------------
+
+func (p Program) tyImportPyModule() *types.Signature {
+	if p.pyImpTy == nil {
+		charPtr := types.NewPointer(types.Typ[types.Int8])
+		objPtr := p.PyObjectPtr().raw.Type
+		params := types.NewTuple(types.NewParam(token.NoPos, nil, "", charPtr))
+		results := types.NewTuple(types.NewParam(token.NoPos, nil, "", objPtr))
+		p.pyImpTy = types.NewSignatureType(nil, nil, nil, params, results, false)
+	}
+	return p.pyImpTy
+}
+
+func (p Program) tyCallNoArg() *types.Signature {
+	if p.callNoArg == nil {
+		objPtr := p.PyObjectPtr().raw.Type
+		paramObjPtr := types.NewParam(token.NoPos, nil, "", objPtr)
+		params := types.NewTuple(paramObjPtr)
+		p.callNoArg = types.NewSignatureType(nil, nil, nil, params, params, false)
+	}
+	return p.callNoArg
+}
+
+func (p Program) tyCallOneArg() *types.Signature {
+	if p.callOneArg == nil {
+		objPtr := p.PyObjectPtr().raw.Type
+		paramObjPtr := types.NewParam(token.NoPos, nil, "", objPtr)
+		params := types.NewTuple(paramObjPtr, paramObjPtr)
+		results := types.NewTuple(paramObjPtr)
+		p.callOneArg = types.NewSignatureType(nil, nil, nil, params, results, false)
+	}
+	return p.callOneArg
+}
+
+// ImportPyMod imports a Python module.
+func (b Builder) ImportPyMod(path string) Expr {
+	pkg := b.Func.Pkg
+	fnImp := pkg.pyFunc("PyImport_ImportModule", b.Prog.tyImportPyModule())
+	return b.Call(fnImp, b.CStr(path))
+}
+
+// NewPyModVar creates a new global variable for a Python module.
+func (p Package) NewPyModVar(name string) Global {
+	prog := p.Prog
+	objPtr := prog.PyObjectPtrPtr().raw.Type
+	g := p.NewVar(name, objPtr, InC)
+	g.Init(prog.Null(g.Type))
+	g.impl.SetLinkage(llvm.LinkOnceAnyLinkage)
+	return g
+}
+
+func (b Builder) pyCall(fn Expr, args []Expr) (ret Expr) {
+	prog := b.Prog
+	pkg := b.Func.Pkg
+	sig := fn.raw.Type.(*types.Signature)
+	params := sig.Params()
+	n := params.Len()
+	switch n {
+	case 0:
+		call := pkg.pyFunc("PyObject_CallNoArg", prog.tyCallNoArg())
+		ret = b.Call(call, fn)
+	case 1:
+		call := pkg.pyFunc("PyObject_CallOneArg", prog.tyCallOneArg())
+		ret = b.Call(call, fn, args[0])
+	default:
+		panic("todo")
+	}
+	return
+}
+
+// -----------------------------------------------------------------------------
diff --git a/ssa/ssa_test.go b/ssa/ssa_test.go
index cc9d8621..17b7ccf5 100644
--- a/ssa/ssa_test.go
+++ b/ssa/ssa_test.go
@@ -25,6 +25,12 @@ import (
 	"github.com/goplus/llvm"
 )
 
+func TestSetPython(t *testing.T) {
+	prog := NewProgram(nil)
+	typ := types.NewPackage("foo", "foo")
+	prog.SetPython(typ)
+}
+
 func TestClosureCtx(t *testing.T) {
 	defer func() {
 		if r := recover(); r == nil {
@@ -106,10 +112,28 @@ func assertPkg(t *testing.T, p Package, expected string) {
 	}
 }
 
+func TestPyFunc(t *testing.T) {
+	prog := NewProgram(nil)
+	py := types.NewPackage("foo", "foo")
+	o := types.NewTypeName(0, py, "Object", nil)
+	types.NewNamed(o, types.Typ[types.Int], nil)
+	py.Scope().Insert(o)
+	prog.SetPython(py)
+	pkg := prog.NewPackage("bar", "foo/bar")
+	sig := types.NewSignatureType(nil, nil, nil, nil, nil, false)
+	a := pkg.NewPyFunc("a", sig)
+	if pkg.NewPyFunc("a", sig) != a {
+		t.Fatal("NewPyFunc(a) failed")
+	}
+}
+
 func TestVar(t *testing.T) {
 	prog := NewProgram(nil)
 	pkg := prog.NewPackage("bar", "foo/bar")
 	a := pkg.NewVar("a", types.Typ[types.Int], InGo)
+	if pkg.NewVar("a", types.Typ[types.Int], InGo) != a {
+		t.Fatal("NewVar(a) failed")
+	}
 	a.Init(prog.Val(100))
 	b := pkg.NewVar("b", types.Typ[types.Int], InGo)
 	b.Init(a.Expr)
diff --git a/ssa/type.go b/ssa/type.go
index 0c3e35ea..936c9b21 100644
--- a/ssa/type.go
+++ b/ssa/type.go
@@ -43,6 +43,7 @@ const (
 	vkFuncDecl
 	vkFuncPtr
 	vkClosure
+	vkPyFunc
 	vkTuple
 	vkPhisExpr = -1
 )
diff --git a/ssa/type_cvt.go b/ssa/type_cvt.go
index e9cbe538..8346577e 100644
--- a/ssa/type_cvt.go
+++ b/ssa/type_cvt.go
@@ -42,6 +42,7 @@ const (
 	inUnknown Background = iota
 	InGo
 	InC
+	InPython
 )
 
 // Type convert a Go/C type into raw type.