diff --git a/file.go b/file.go
index 7bd2b1b..21a7630 100644
--- a/file.go
+++ b/file.go
@@ -1,5 +1,14 @@
 package main
 
+import (
+	"bufio"
+	"crypto/md5"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"strings"
+)
+
 type ClocFile struct {
 	Code     int32  `xml:"code,attr"`
 	Comments int32  `xml:"comment,attr"`
@@ -19,3 +28,117 @@ func (cf ClocFiles) Swap(i, j int) {
 func (cf ClocFiles) Less(i, j int) bool {
 	return cf[i].Code > cf[j].Code
 }
+
+var fileCache map[string]struct{}
+
+func analyzeFile(filename string, language *Language) *ClocFile {
+	clocFile := &ClocFile{
+		Name: filename,
+	}
+
+	fp, err := os.Open(filename)
+	if err != nil {
+		return clocFile // ignore error
+	}
+	defer fp.Close()
+
+	isFirstLine := true
+	isInComments := false
+	isInCommentsSame := false
+	scanner := bufio.NewScanner(fp)
+	for scanner.Scan() {
+		lineOrg := scanner.Text()
+		line := strings.TrimSpace(lineOrg)
+
+		if len(strings.TrimSpace(line)) == 0 {
+			clocFile.Blanks += 1
+			if opts.Debug {
+				fmt.Printf("[BLNK,cd:%d,cm:%d,bk:%d,iscm:%v] %s\n",
+					clocFile.Code, clocFile.Comments, clocFile.Blanks, isInComments, lineOrg)
+			}
+			continue
+		}
+
+		if language.multi_line != "" {
+			if strings.HasPrefix(line, language.multi_line) {
+				isInComments = true
+			} else if containComments(line, language.multi_line, language.multi_line_end) {
+				isInComments = true
+				clocFile.Code += 1
+			}
+		}
+
+		if isInComments {
+			if language.multi_line == language.multi_line_end {
+				if strings.Count(line, language.multi_line_end) == 2 {
+					isInComments = false
+					isInCommentsSame = false
+				} else if strings.HasPrefix(line, language.multi_line_end) {
+					if isInCommentsSame {
+						isInComments = false
+					}
+					isInCommentsSame = !isInCommentsSame
+				}
+			} else {
+				if strings.Contains(line, language.multi_line_end) {
+					isInComments = false
+				}
+			}
+			clocFile.Comments += 1
+			if opts.Debug {
+				fmt.Printf("[COMM,cd:%d,cm:%d,bk:%d,iscm:%v,iscms:%v] %s\n",
+					clocFile.Code, clocFile.Comments, clocFile.Blanks, isInComments, isInCommentsSame, lineOrg)
+			}
+			continue
+		}
+
+		// shebang line is 'code'
+		if isFirstLine && strings.HasPrefix(line, "#!") {
+			clocFile.Code += 1
+			isFirstLine = false
+			if opts.Debug {
+				fmt.Printf("[CODE,cd:%d,cm:%d,bk:%d,iscm:%v] %s\n",
+					clocFile.Code, clocFile.Comments, clocFile.Blanks, isInComments, lineOrg)
+			}
+			continue
+		}
+
+		if language.line_comment != "" {
+			single_comments := strings.Split(language.line_comment, ",")
+			isSingleComment := false
+			for _, single_comment := range single_comments {
+				if strings.HasPrefix(line, single_comment) {
+					clocFile.Comments += 1
+					isSingleComment = true
+					break
+				}
+			}
+			if isSingleComment {
+				if opts.Debug {
+					fmt.Printf("[COMM,cd:%d,cm:%d,bk:%d,iscm:%v] %s\n",
+						clocFile.Code, clocFile.Comments, clocFile.Blanks, isInComments, lineOrg)
+				}
+				continue
+			}
+		}
+
+		clocFile.Code += 1
+		if opts.Debug {
+			fmt.Printf("[CODE,cd:%d,cm:%d,bk:%d,iscm:%v] %s\n",
+				clocFile.Code, clocFile.Comments, clocFile.Blanks, isInComments, lineOrg)
+		}
+	}
+
+	// uniq file detect & ignore
+	// FIXME: not used, now
+	if ret, err := fp.Seek(0, 0); ret != 0 || err != nil {
+		panic(err)
+	}
+	if d, err := ioutil.ReadAll(fp); err == nil {
+		hash := md5.Sum(d)
+		c := fmt.Sprintf("%x", hash)
+		fileCache[c] = struct{}{}
+	}
+
+	return clocFile
+}
diff --git a/main.go b/main.go
index 7349c11..4f139f5 100644
--- a/main.go
+++ b/main.go
@@ -1,10 +1,7 @@
 package main
 
 import (
-	"bufio"
-	"crypto/md5"
 	"fmt"
-	"io/ioutil"
 	"os"
 	"regexp"
 	"sort"
@@ -100,7 +97,7 @@ func main() {
 	polly := NewLanguage("Polly", "<!--", "<!--", "-->")
 	perl := NewLanguage("Perl", "#", ":=", ":=cut")
 	protobuf := NewLanguage("Protocol Buffers", "//", "", "")
-	python := NewLanguage("Python", "#", "'''", "'''")
+	python := NewLanguage("Python", "#", "\"\"\"", "\"\"\"")
 	r := NewLanguage("R", "#", "", "")
 	ruby := NewLanguage("Ruby", "#", ":=begin", ":=end")
 	ruby_html := NewLanguage("Ruby HTML", "<!--", "<!--", "-->")
@@ -209,7 +206,7 @@ func main() {
 	}
 
 	clocFiles := make(map[string]*ClocFile, num)
-	fileCache := make(map[string]bool)
+	fileCache = make(map[string]struct{})
 
 	for _, language := range languages {
 		if language.printed {
@@ -217,81 +214,7 @@ func main() {
 		}
 
 		for _, file := range language.files {
-			clocFiles[file] = &ClocFile{
-				Name: file,
-			}
-			isInComments := false
-
-			func() {
-				fp, err := os.Open(file)
-				if err != nil {
-					return // ignore error
-				}
-				defer fp.Close()
-
-				isFirstLine := true
-				scanner := bufio.NewScanner(fp)
-				for scanner.Scan() {
-					line := strings.TrimSpace(scanner.Text())
-
-					if len(strings.TrimSpace(line)) == 0 {
-						clocFiles[file].Blanks += 1
-						continue
-					}
-
-					if language.multi_line != "" {
-						if strings.HasPrefix(line, language.multi_line) {
-							isInComments = true
-						} else if containComments(line, language.multi_line, language.multi_line_end) {
-							isInComments = true
-							clocFiles[file].Code += 1
-						}
-					}
-
-					if isInComments {
-						if strings.Contains(line, language.multi_line_end) {
-							isInComments = false
-						}
-						clocFiles[file].Comments += 1
-						continue
-					}
-
-					// shebang line is 'code'
-					if isFirstLine && strings.HasPrefix(line, "#!") {
-						clocFiles[file].Code += 1
-						isFirstLine = false
-						continue
-					}
-
-					if language.line_comment != "" {
-						single_comments := strings.Split(language.line_comment, ",")
-						isSingleComment := false
-						for _, single_comment := range single_comments {
-							if strings.HasPrefix(line, single_comment) {
-								clocFiles[file].Comments += 1
-								isSingleComment = true
-								break
-							}
-						}
-						if isSingleComment {
-							continue
-						}
-					}
-
-					clocFiles[file].Code += 1
-				}
-
-				// uniq file detect & ignore
-				// FIXME: not used, now
-				if ret, err := fp.Seek(0, 0); ret != 0 || err != nil {
-					panic(err)
-				}
-				if d, err := ioutil.ReadAll(fp); err == nil {
-					hash := md5.Sum(d)
-					c := fmt.Sprintf("%x", hash)
-					fileCache[c] = true
-				}
-			}()
+			clocFiles[file] = analyzeFile(file, language)
 
 			language.code += clocFiles[file].Code
 			language.comments += clocFiles[file].Comments
diff --git a/option.go b/option.go
index 574bec1..99bb3f7 100644
--- a/option.go
+++ b/option.go
@@ -8,6 +8,7 @@ type Options struct {
 	OutputType  string `long:"output-type" default:"default" description:"output type [values: default,cloc-xml,sloccount]"`
 	ExcludeExt  string `long:"exclude-ext" description:"exclude file name extensions (separated commas)"`
 	NotMatchDir string `long:"not-match-d" description:"exclude dir name (regex)"`
+	Debug       bool   `long:"debug" description:"dump debug log for developer"`
 }
 
 const OutputTypeDefault string = "default"