fn: add support for python (#328)

fn/common.go

@@ -232,7 +232,7 @@ var acceptableFnRuntimes = map[string]string{
 	"node":      "iron/node",
 	"perl":      "iron/perl",
 	"php":       "iron/php",
-	"python":    "iron/python",
+	"python":    "iron/python:2",
 	"ruby":      "iron/ruby",
 	"scala":     "iron/scala",
 }

fn/init.go

@@ -26,6 +26,7 @@ var (
 		".go": "go",
 		".js": "node",
 		".rb": "ruby",
+		".py": "python",
 	}
 
 	fnInitRuntimes []string

fn/langs/base.go

@@ -11,6 +11,8 @@ func GetLangHelper(lang string) (LangHelper, error) {
 		return &NodeLangHelper{}, nil
 	case "ruby":
 		return &RubyLangHelper{}, nil
+	case "python":
+		return &PythonHelper{}, nil
 	}
 	return nil, fmt.Errorf("No language helper found for %v", lang)
 }

fn/langs/python.go

@@ -0,0 +1,44 @@
+package langs
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+)
+
+type PythonHelper struct {
+}
+
+func (lh *PythonHelper) Entrypoint() string {
+	return "python2 func.py"
+}
+
+func (lh *PythonHelper) HasPreBuild() bool {
+	return true
+}
+
+// PreBuild for Go builds the binary so the final image can be as small as possible
+func (lh *PythonHelper) PreBuild() error {
+	wd, err := os.Getwd()
+	if err != nil {
+		return err
+	}
+
+	pbcmd := fmt.Sprintf("docker run --rm -v %s:/worker -w /worker iron/python:2-dev pip install -t packages -r requirements.txt", wd)
+	fmt.Println("Running prebuild command:", pbcmd)
+	parts := strings.Fields(pbcmd)
+	head := parts[0]
+	parts = parts[1:len(parts)]
+	cmd := exec.Command(head, parts...)
+	cmd.Stderr = os.Stderr
+	cmd.Stdout = os.Stdout
+	if err := cmd.Run(); err != nil {
+		return fmt.Errorf("error running docker build: %v", err)
+	}
+	return nil
+}
+
+func (lh *PythonHelper) AfterBuild() error {
+	return nil
+}