diff --git a/apk2java.py b/apk2java.py
index 5b40eaa..aea6169 100755
--- a/apk2java.py
+++ b/apk2java.py
@@ -5,188 +5,209 @@
 import sys, os, string
 import urllib.request
 import zipfile
-from subprocess import call
+import subprocess
 from optparse import OptionParser
 
-apk_file=''
-apk_folder=''
-project_name=''
-sign_file=''
-cwd=os.path.dirname(os.path.abspath(__file__))
-home=os.path.dirname(os.path.realpath(sys.argv[0]))
-outdir=os.path.dirname(os.path.realpath(sys.argv[1]))
-external="https://github.com/TheZ3ro/apk2java-linux/releases/download/tool/tool.zip"
+
+def call(cmd, **kwargs):
+    print('Running: {0}'.format(' '.join(cmd)))
+    return subprocess.call(cmd, **kwargs)
+
+
+apk_file = ''
+apk_folder = ''
+project_name = ''
+sign_file = ''
+cwd = os.path.dirname(os.path.abspath(__file__))
+home = os.path.dirname(os.path.realpath(sys.argv[0]))
+outdir = os.path.dirname(os.path.realpath(sys.argv[1]))
+external = "https://github.com/TheZ3ro/apk2java-linux/releases/download/tool/tool.zip"
+
 
 def check_home(path):
-  return os.path.isdir(path+"/tool")
+    return os.path.isdir(path + "/tool")
+
 
 def getunzipped(theurl, thedir, report):
-  if not os.path.exists(thedir):
-    os.mkdir(thedir)
-  print ("Downloading external tool... -> "+thedir+"/tool/")
-  name = os.path.join(thedir, 'temp.zip')
-  try:
-    name, hdrs = urllib.request.urlretrieve(theurl, name, report)
-  except IOError as e:
-    print ("Can't retrieve %r to %r: %s" % (theurl, thedir, e))
-    return
-  try:
-    z = zipfile.ZipFile(name)
-  except zipfile.error as e:
-    print ("Bad zipfile (from %r): %s" % (theurl, e))
-    return
-  for n in z.namelist():
-    (dirname, filename) = os.path.split(n)
-    perm = ((z.getinfo(n).external_attr >> 16) & 0x0777)
-    if filename == '':
-      # directory
-      newdir = thedir + '/' + dirname
-      if not os.path.exists(newdir):
-          os.mkdir(newdir)
-    else:
-      # file
-      fd = os.open(thedir+"/"+n, os.O_CREAT | os.O_WRONLY, perm)
-      os.write(fd, z.read(n))
-      os.close(fd)
-  z.close()
-  os.unlink(name)
-  print ("")
+    if not os.path.exists(thedir):
+        os.mkdir(thedir)
+    print("Downloading external tool... -> " + thedir + "/tool/")
+    name = os.path.join(thedir, 'temp.zip')
+    try:
+        name, hdrs = urllib.request.urlretrieve(theurl, name, report)
+    except IOError as e:
+        print("Can't retrieve %r to %r: %s" % (theurl, thedir, e))
+        return
+    try:
+        z = zipfile.ZipFile(name)
+    except zipfile.error as e:
+        print("Bad zipfile (from %r): %s" % (theurl, e))
+        return
+    for n in z.namelist():
+        (dirname, filename) = os.path.split(n)
+        perm = ((z.getinfo(n).external_attr >> 16) & 0x0777)
+        if filename == '':
+            # directory
+            newdir = thedir + '/' + dirname
+            if not os.path.exists(newdir):
+                os.mkdir(newdir)
+        else:
+            # file
+            fd = os.open(thedir + "/" + n, os.O_CREAT | os.O_WRONLY, perm)
+            os.write(fd, z.read(n))
+            os.close(fd)
+    z.close()
+    os.unlink(name)
+    print("")
+
 
 def report(blocknr, blocksize, size):
-  current = blocknr*blocksize
-  sys.stdout.write("\rProgress: {0:.2f}%".format(100.0*current/size)+" - {0:.1f} MB".format(current/1024/1024)+"/{0:.1f} MB".format(size/1024/1024))
+    current = blocknr * blocksize
+    sys.stdout.write("\rProgress: {0:.2f}%".format(100.0 * current / size) + " - {0:.1f} MB".format(
+        current / 1024 / 1024) + "/{0:.1f} MB".format(size / 1024 / 1024))
+
+
+def print_header(text):
+    block = "*********************************************"
+    print(block)
+    print('**' + text.center(len(block) - 4) + '**')
+    print(block)
+
 
 def apktool(smali):
-  print ("*********************************************")
-  print ("**      Extract, fix resource files        **")
-  print ("*********************************************")
-  if apk_file != '':
-    if smali == True:
-      call(home+'/tool/apktool_200rc3.jar d '+apk_file+' -o '+outdir+project_name+' -f',shell=True)
-    else:
-      call(home+'/tool/apktool_200rc3.jar d '+apk_file+' -o '+outdir+project_name+' -sf',shell=True)
-      os.system('mv %s %s' % (outdir+project_name+'/classes.dex', outdir+project_name+'/original/'))
-  print ('Done')
+    print_header('Extract, fix resource files')
+    if apk_file != '':
+        cmd = [home + '/tool/apktool_200rc3.jar', 'd', apk_file, '-o', outdir + project_name, '-f']
+
+        if smali:
+            cmd[-1] = '-sf'
+
+        call(cmd)
+        call(['mv', outdir + project_name + '/classes.dex', outdir + project_name + '/original/'])
+    print('Done')
+
 
 def dex2jar():
-  print ("*********************************************")
-  print ("**          Convert 'apk' to 'jar'         **")
-  print ("*********************************************")
-  if apk_file != '':
-    call(home+'/tool/dex2jar-0.0.9.15/d2j-dex2jar.sh -f -o '+outdir+project_name+'.jar '+apk_file, shell=True)
-    call(home+'/tool/dex2jar-0.0.9.15/d2j-asm-verify.sh '+outdir+project_name+'.jar',shell=True)
-    print ('Done')
+    print_header("Convert 'apk' to 'jar'")
+    if apk_file != '':
+        call([home + '/tool/dex2jar-0.0.9.15/d2j-dex2jar.sh', '-f', '-o', outdir + project_name + '.jar', apk_file])
+        call([home + '/tool/dex2jar-0.0.9.15/d2j-asm-verify.sh', outdir + project_name + '.jar'])
+        print('Done')
+
 
 def procyon():
-  print ("*********************************************")
-  print ("**        Decompiling class files          **")
-  print ("*********************************************")
-  if apk_file != '':
-    call(home+'/tool/procyon-decompiler-0528.jar -jar '+outdir+project_name+'.jar -o '+outdir+project_name+'/src/',shell=True)
-    print ('Done')
+    print_header('Decompiling class files')
+    if apk_file != '':
+        call([home + '/tool/procyon-decompiler-0528.jar', '-jar', outdir + project_name + '.jar',
+              '-o', outdir + project_name + '/src/'])
+        print('Done')
+
 
 def apktool_build():
-  print ("*********************************************")
-  print ("**        Building apk from smali          **")
-  print ("*********************************************")
-  if apk_folder != '':
-    call(home+'/tool/apktool_200rc3.jar b '+apk_folder+' -o '+outdir+project_name+'-rebuild.apk',shell=True)
-    global sign_file
-    sign_file = outdir+project_name+'-rebuild.apk'
-    print ('Done')
+    print_header('Building apk from smali')
+    if apk_folder != '':
+        call([home + '/tool/apktool_200rc3.jar', 'b', apk_folder, '-o', outdir + project_name + '-rebuild.apk'])
+        global sign_file
+        sign_file = outdir + project_name + '-rebuild.apk'
+        print('Done')
+
 
 def jar2jasmin():
-  print ("*********************************************")
-  print ("**        Convert 'jar' to 'jasmin'        **")
-  print ("*********************************************")
-  if apk_file != '':
-    call(home+'/tool/dex2jar-0.0.9.15/d2j-jar2jasmin.sh -f -o '+outdir+project_name+'/jasmin '+outdir+project_name+'.jar',shell=True)
-    print ('Done')
+    print_header("Convert 'jar' to 'jasmin'")
+    if apk_file != '':
+        call([home + '/tool/dex2jar-0.0.9.15/d2j-jar2jasmin.sh', '-f', '-o', outdir + project_name + '/jasmin',
+              outdir + project_name + '.jar'])
+        print('Done')
+
 
 def jasmin_build():
-  print ("*********************************************")
-  print ("**          Build apk from jasmin          **")
-  print ("*********************************************")
-  if apk_folder != '':
-    call(home+'/tool/dex2jar-0.0.9.15/d2j-jasmin2jar.sh -f -o '+outdir+project_name+'-new.jar '+outdir+project_name+'/jasmin',shell=True)
-    call(home+'/tool/dex2jar-0.0.9.15/d2j-asm-verify.sh '+outdir+project_name+'-new.jar',shell=True)
-    call(home+'/tool/dex2jar-0.0.9.15/d2j-jar2dex.sh -f -o '+outdir+project_name+'/classes.dex '+outdir+project_name+'-new.jar',shell=True)
-    call('zip -r '+outdir+project_name+'-new.apk -j '+outdir+project_name+'/classes.dex',shell=True)
-    global sign_file
-    sign_file = outdir+project_name+'-new.apk'
-    print ('Done')
+    print_header('Build apk from jasmin')
+    if apk_folder != '':
+        call([home + '/tool/dex2jar-0.0.9.15/d2j-jasmin2jar.sh', '-f', '-o', outdir + project_name + '-new.jar',
+              outdir + project_name + '/jasmin'])
+        call([home + '/tool/dex2jar-0.0.9.15/d2j-asm-verify.sh', outdir + project_name + '-new.jar'])
+        call([home + '/tool/dex2jar-0.0.9.15/d2j-jar2dex.sh', '-f', '-o', outdir + project_name + '/classes.dex',
+              outdir + project_name + '-new.jar'])
+        call(['zip', '-r ' + outdir + project_name + '-new.apk', '-j', outdir + project_name + '/classes.dex'])
+        global sign_file
+        sign_file = outdir + project_name + '-new.apk'
+        print('Done')
+
 
 def sign():
-  print ("*********************************************")
-  print ("**                Sign apk                 **")
-  print ("*********************************************")
-  call(home+'/tool/dex2jar-0.0.9.15/d2j-apk-sign.sh -f -o '+outdir+project_name+'-signed.apk '+sign_file,shell=True)
-  print ('Done')
+    print_header('Sign apk')
+    call([home + '/tool/dex2jar-0.0.9.15/d2j-apk-sign.sh', '-f', '-o', outdir + project_name + '-signed.apk',
+          sign_file])
+    print('Done')
+
 
 def main():
-  global apk_folder,apk_file,project_name,home,outdir
-  usage = "usage: %prog action file [options]"
-  parser = OptionParser(usage=usage)
-  parser.add_option("--java",action="store_true", dest="java", default=True, help="select java source format [DEFAULT]")
-  parser.add_option("--smali",action="store_true", dest="smali", default=False, help="select smali source format")
-  parser.add_option("--jasmin",action="store_true", dest="jasmin", default=False, help="select jasmin source format")
-  parser.add_option("--no-source",action="store_true", dest="nosc", default=False, help="no source code generation")
-  parser.add_option("-o", dest="outdir", default=cwd+"/", help="specify the output directory "
-	+"(if not specified the decomipled version will be store in a folder in the script directory)")
-  (options, args) = parser.parse_args()
-
-  if home == cwd+"/apk2java":
-    if check_home(home) == False:
-      getunzipped(external, home, report)
-  else:
-    if check_home(home) == False:
-      if check_home(cwd+"/apk2java") == False:
-        getunzipped(external, cwd+"/apk2java", report)
-        home = cwd+"/apk2java"
-      else:
-        home = cwd+"/apk2java"
-  outdir = options.outdir
-
-  if (options.smali+options.jasmin+options.nosc) > 1:
-    print ("[ ERROR ] You can only select 1 source format --[smali/jasmin/java/no-source]")
-    exit(1)
-  if len(args)==2:
-    if args[0] == 'd':
-      if os.path.isfile(args[1]) and os.path.splitext(args[1])[-1].lower() == '.apk':
-        apk_file = args[1]
-        project_name = os.path.splitext(os.path.basename(args[1]))[0].lower()
-        if not os.path.exists(outdir):
-          os.makedirs(outdir)
-        call("cp "+apk_file+" "+outdir+project_name+"-new.apk",shell=True)
-        if options.jasmin == True:
-          dex2jar()
-          jar2jasmin()
-        else:
-          apktool(options.smali)
-          if options.smali == False and options.nosc == False:
-            dex2jar()
-            procyon()
-        call("cp "+tmp+project_name+"/ ./ -R",shell=True)
-      else:
-        print ("[ ERROR ] You must select a valid APK file!")
+    global apk_folder, apk_file, project_name, home, outdir
+    usage = "usage: %prog action file [options]"
+    parser = OptionParser(usage=usage)
+    parser.add_option("--java", action="store_true", dest="java", default=True,
+                      help="select java source format [DEFAULT]")
+    parser.add_option("--smali", action="store_true", dest="smali", default=False, help="select smali source format")
+    parser.add_option("--jasmin", action="store_true", dest="jasmin", default=False, help="select jasmin source format")
+    parser.add_option("--no-source", action="store_true", dest="nosc", default=False, help="no source code generation")
+    parser.add_option("-o", dest="outdir", default=cwd + "/", help="specify the output directory "
+                                                                   + "(if not specified the decomipled version will be store in a folder in the script directory)")
+    (options, args) = parser.parse_args()
+
+    if home == cwd + "/apk2java":
+        if check_home(home) == False:
+            getunzipped(external, home, report)
+    else:
+        if check_home(home) == False:
+            if check_home(cwd + "/apk2java") == False:
+                getunzipped(external, cwd + "/apk2java", report)
+                home = cwd + "/apk2java"
+            else:
+                home = cwd + "/apk2java"
+    outdir = options.outdir
+
+    if (options.smali + options.jasmin + options.nosc) > 1:
+        print("[ ERROR ] You can only select 1 source format --[smali/jasmin/java/no-source]")
         exit(1)
-    elif args[0] == 'b':
-      if os.path.isdir(args[1]):
-        apk_folder = args[1]
-        project_name = os.path.basename(os.path.dirname(args[1]).lower())
-        if options.jasmin == True:
-          jasmin_build()
-        elif options.smali == True:
-          apktool_build()
+    if len(args) == 2:
+        if args[0] == 'd':
+            if os.path.isfile(args[1]) and os.path.splitext(args[1])[-1].lower() == '.apk':
+                apk_file = args[1]
+                project_name = os.path.splitext(os.path.basename(args[1]))[0].lower()
+                if not os.path.exists(outdir):
+                    os.makedirs(outdir)
+
+                call(["cp", apk_file, outdir + project_name + "-new.apk"])
+                if options.jasmin == True:
+                    dex2jar()
+                    jar2jasmin()
+                else:
+                    apktool(options.smali)
+                    if options.smali == False and options.nosc == False:
+                        dex2jar()
+                        procyon()
+                call(["cp", tmp + project_name + "/", "./", "-R"])
+            else:
+                print("[ ERROR ] You must select a valid APK file!")
+                exit(1)
+        elif args[0] == 'b':
+            if os.path.isdir(args[1]):
+                apk_folder = args[1]
+                project_name = os.path.basename(os.path.dirname(args[1]).lower())
+                if options.jasmin == True:
+                    jasmin_build()
+                elif options.smali == True:
+                    apktool_build()
+                else:
+                    print("[ ERROR ] Can't build apk with that source format. Only Jasmin or Smali supported")
+                sign()
+                call(["cp", sign_file, "./", ])
         else:
-          print ("[ ERROR ] Can't build apk with that source format. Only Jasmin or Smali supported")
-        sign()
-        call("cp "+sign_file+" ./",shell=True)
+            parser.error("action can be only 'b' (build) or 'd' (decompile)")
     else:
-      parser.error("action can be only 'b' (build) or 'd' (decompile)")
-  else:
-    parser.print_help()
+        parser.print_help()
+
 
 # Script start Here
-if __name__=="__main__":
-  main()
+if __name__ == "__main__":
+    main()