diff --git a/patoolib/programs/arc.py b/patoolib/programs/arc.py
index c89dba9..8eadaf2 100644
--- a/patoolib/programs/arc.py
+++ b/patoolib/programs/arc.py
@@ -17,6 +17,7 @@
 import os
 from ..util import PatoolError
 
+
 def _add_password_to_options(options, password):
     """Check password and add it to ARC options."""
     if password is None:
@@ -26,6 +27,7 @@ def _add_password_to_options(options, password):
     options += 'g%s' % password
     return options
 
+
 def extract_arc (archive, compression, cmd, verbosity, interactive, outdir, password=None):
     """Extract a ARC archive."""
     # Since extracted files will be placed in the current directory,
@@ -34,6 +36,7 @@ def extract_arc (archive, compression, cmd, verbosity, interactive, outdir, pass
     cmdlist = [cmd, options, os.path.abspath(archive)]
     return (cmdlist, {'cwd': outdir})
 
+
 def list_arc (archive, compression, cmd, verbosity, interactive, password=None):
     """List a ARC archive."""
     cmdlist = [cmd]
@@ -44,10 +47,12 @@ def list_arc (archive, compression, cmd, verbosity, interactive, password=None):
     cmdlist.append(archive)
     return cmdlist
 
+
 def test_arc (archive, compression, cmd, verbosity, interactive, password=None):
     """Test a ARC archive."""
     return [cmd, _add_password_to_options('t', password), archive]
 
+
 def create_arc (archive, compression, cmd, verbosity, interactive, filenames, password=None):
     """Create a ARC archive."""
     cmdlist = [cmd, _add_password_to_options('a', password), archive]
diff --git a/patoolib/programs/arj.py b/patoolib/programs/arj.py
index d1f5e33..9fb751f 100644
--- a/patoolib/programs/arj.py
+++ b/patoolib/programs/arj.py
@@ -22,11 +22,15 @@ def _get_password_switch(password):
         raise PatoolError("Password for ARJ can't contain spaces.")
     return '-g%s' % password
 
+def _maybe_add_password(cmdlist, password):
+    if password:
+        cmdlist.append(_get_password_switch(password))
+
+
 def extract_arj (archive, compression, cmd, verbosity, interactive, outdir, password=None):
     """Extract an ARJ archive."""
     cmdlist = [cmd, 'x', '-r']
-    if password:
-        cmdlist.append(_get_password_switch(password))
+    _maybe_add_password(cmdlist, password)
     if not interactive:
         cmdlist.append('-y')
     cmdlist.extend([archive, outdir])
@@ -36,8 +40,7 @@ def extract_arj (archive, compression, cmd, verbosity, interactive, outdir, pass
 def list_arj (archive, compression, cmd, verbosity, interactive, password=None):
     """List an ARJ archive."""
     cmdlist = [cmd]
-    if password:
-        cmdlist.append(_get_password_switch(password))
+    _maybe_add_password(cmdlist, password)
     if verbosity > 1:
         cmdlist.append('v')
     else:
@@ -51,8 +54,7 @@ def list_arj (archive, compression, cmd, verbosity, interactive, password=None):
 def test_arj (archive, compression, cmd, verbosity, interactive, password=None):
     """Test an ARJ archive."""
     cmdlist = [cmd, 't', '-r']
-    if password:
-        cmdlist.append(_get_password_switch(password))
+    _maybe_add_password(cmdlist, password)
     if not interactive:
         cmdlist.append('-y')
     cmdlist.append(archive)
@@ -62,8 +64,7 @@ def test_arj (archive, compression, cmd, verbosity, interactive, password=None):
 def create_arj (archive, compression, cmd, verbosity, interactive, filenames, password=None):
     """Create an ARJ archive."""
     cmdlist = [cmd, 'a', '-r']
-    if password:
-        cmdlist.append(_get_password_switch(password))
+    _maybe_add_password(cmdlist, password)
     if not interactive:
         cmdlist.append('-y')
     cmdlist.append(archive)
diff --git a/patoolib/programs/p7zip.py b/patoolib/programs/p7zip.py
index 45e8483..ee1865a 100644
--- a/patoolib/programs/p7zip.py
+++ b/patoolib/programs/p7zip.py
@@ -15,13 +15,16 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 """Archive commands for the 7z program."""
 
+def _maybe_add_password(cmdlist, password):
+    if password:
+        cmdlist.append('-p%s' % password)
+
 def extract_7z(archive, compression, cmd, verbosity, interactive, outdir, password=None):
     """Extract a 7z archive."""
     cmdlist = [cmd, 'x']
     if not interactive:
         cmdlist.append('-y')
-    if password:
-        cmdlist.append('-p%s' % password)
+    _maybe_add_password(cmdlist, password)
     cmdlist.extend(['-o%s' % outdir, '--', archive])
     return cmdlist
 
@@ -32,8 +35,7 @@ def extract_7z_singlefile(archive, compression, cmd, verbosity, interactive, out
     cmdlist = [cmd, 'e']
     if not interactive:
         cmdlist.append('-y')
-    if password:
-        cmdlist.append('-p%s' % password)
+    _maybe_add_password(cmdlist, password)
     cmdlist.extend(['-o%s' % outdir, '--', archive])
     return cmdlist
 
@@ -60,8 +62,7 @@ def list_7z (archive, compression, cmd, verbosity, interactive, password=None):
     cmdlist = [cmd, 'l']
     if not interactive:
         cmdlist.append('-y')
-    if password:
-        cmdlist.append('-p%s' % password)
+    _maybe_add_password(cmdlist, password)
     cmdlist.extend(['--', archive])
     return cmdlist
 
@@ -87,8 +88,7 @@ def test_7z (archive, compression, cmd, verbosity, interactive, password=None):
     cmdlist = [cmd, 't']
     if not interactive:
         cmdlist.append('-y')
-    if password:
-        cmdlist.append('-p%s' % password)
+    _maybe_add_password(cmdlist, password)
     cmdlist.extend(['--', archive])
     return cmdlist
 
@@ -114,8 +114,7 @@ def create_7z(archive, compression, cmd, verbosity, interactive, filenames, pass
     cmdlist = [cmd, 'a']
     if not interactive:
         cmdlist.append('-y')
-    if password:
-        cmdlist.append('-p%s' % password)
+    _maybe_add_password(cmdlist, password)
     cmdlist.extend(['-t7z', '-mx=9', '--', archive])
     cmdlist.extend(filenames)
     return cmdlist
@@ -126,8 +125,7 @@ def create_zip(archive, compression, cmd, verbosity, interactive, filenames, pas
     cmdlist = [cmd, 'a']
     if not interactive:
         cmdlist.append('-y')
-    if password:
-        cmdlist.append('-p%s' % password)
+    _maybe_add_password(cmdlist, password)
     cmdlist.extend(['-tzip', '-mx=9', '--', archive])
     cmdlist.extend(filenames)
     return cmdlist
@@ -138,8 +136,7 @@ def create_xz(archive, compression, cmd, verbosity, interactive, filenames, pass
     cmdlist = [cmd, 'a']
     if not interactive:
         cmdlist.append('-y')
-    if password:
-        cmdlist.append('-p%s' % password)
+    _maybe_add_password(cmdlist, password)
     cmdlist.extend(['-txz', '-mx=9', '--', archive])
     cmdlist.extend(filenames)
     return cmdlist
@@ -150,8 +147,7 @@ def create_gzip(archive, compression, cmd, verbosity, interactive, filenames, pa
     cmdlist = [cmd, 'a']
     if not interactive:
         cmdlist.append('-y')
-    if password:
-        cmdlist.append('-p%s' % password)
+    _maybe_add_password(cmdlist, password)
     cmdlist.extend(['-tgzip', '-mx=9', '--', archive])
     cmdlist.extend(filenames)
     return cmdlist
@@ -162,8 +158,7 @@ def create_bzip2(archive, compression, cmd, verbosity, interactive, filenames, p
     cmdlist = [cmd, 'a']
     if not interactive:
         cmdlist.append('-y')
-    if password:
-        cmdlist.append('-p%s' % password)
+    _maybe_add_password(cmdlist, password)
     cmdlist.extend(['-tbzip2', '-mx=9', '--', archive])
     cmdlist.extend(filenames)
     return cmdlist
diff --git a/patoolib/programs/unalz.py b/patoolib/programs/unalz.py
index 9e2f69c..4bb64d2 100644
--- a/patoolib/programs/unalz.py
+++ b/patoolib/programs/unalz.py
@@ -15,11 +15,15 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 """Archive commands for the unalz program."""
 
+def _maybe_add_password(cmdlist, password):
+    if password:
+        cmdlist.extend(['-pwd', password])
+
+
 def extract_alzip (archive, compression, cmd, verbosity, interactive, outdir, password=None):
     """Extract a ALZIP archive."""
     cmdlist = [cmd, '-d', outdir]
-    if password:
-        cmdlist.extend(['-pwd', password])
+    _maybe_add_password(cmdlist, password)
     cmdlist.append(archive)
     return cmdlist
 
@@ -27,8 +31,7 @@ def extract_alzip (archive, compression, cmd, verbosity, interactive, outdir, pa
 def list_alzip (archive, compression, cmd, verbosity, interactive, password=None):
     """List a ALZIP archive."""
     cmdlist = [cmd, '-l']
-    if password:
-        cmdlist.extend(['-pwd', password])
+    _maybe_add_password(cmdlist, password)
     cmdlist.append(archive)
     return cmdlist
 
diff --git a/patoolib/programs/unzip.py b/patoolib/programs/unzip.py
index 2b875b9..b87e497 100644
--- a/patoolib/programs/unzip.py
+++ b/patoolib/programs/unzip.py
@@ -15,13 +15,16 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 """Archive commands for the unzip program."""
 
+def _maybe_add_password(cmdlist, password):
+    if password:
+        cmdlist.extend(['-P', password])
+
 def extract_zip (archive, compression, cmd, verbosity, interactive, outdir, password=None):
     """Extract a ZIP archive."""
     cmdlist = [cmd]
     if verbosity > 1:
         cmdlist.append('-v')
-    if password:
-        cmdlist.extend(['-P', password])
+    _maybe_add_password(cmdlist, password)
     cmdlist.extend(['--', archive, '-d', outdir])
     return cmdlist
 
@@ -30,8 +33,7 @@ def list_zip (archive, compression, cmd, verbosity, interactive, password=None):
     cmdlist = [cmd, '-l']
     if verbosity > 1:
         cmdlist.append('-v')
-    if password:
-        cmdlist.extend(['-P', password])
+    _maybe_add_password(cmdlist, password)
     cmdlist.extend(['--', archive])
     return cmdlist
 
@@ -40,7 +42,6 @@ def test_zip (archive, compression, cmd, verbosity, interactive, password=None):
     cmdlist = [cmd, '-t']
     if verbosity > 1:
         cmdlist.append('-v')
-    if password:
-        cmdlist.extend(['-P', password])
+    _maybe_add_password(cmdlist, password)
     cmdlist.extend(['--', archive])
     return cmdlist
diff --git a/patoolib/programs/xdms.py b/patoolib/programs/xdms.py
index d76048d..a05fe8f 100644
--- a/patoolib/programs/xdms.py
+++ b/patoolib/programs/xdms.py
@@ -17,14 +17,18 @@
 from .. import util
 
 
+def _maybe_add_password(cmdlist, password):
+    if password:
+        cmdlist.extend(['-p', password])
+
+
 def extract_dms (archive, compression, cmd, verbosity, interactive, outdir, password=None):
     """Extract a DMS archive."""
     check_archive_ext(archive)
     cmdlist = [cmd, '-d', outdir]
     if verbosity > 1:
         cmdlist.append('-v')
-    if password:
-        cmdlist.extend(['-p', password])
+    _maybe_add_password(cmdlist, password)
     cmdlist.extend(['u', archive])
     return cmdlist
 
@@ -33,8 +37,7 @@ def list_dms (archive, compression, cmd, verbosity, interactive, password=None):
     """List a DMS archive."""
     check_archive_ext(archive)
     cmdlist = [cmd, 'v']
-    if password:
-        cmdlist.extend(['-p', password])
+    _maybe_add_password(cmdlist, password)
     cmdlist.append(archive)
     return cmdlist
 
@@ -43,8 +46,7 @@ def test_dms (archive, compression, cmd, verbosity, interactive, password=None):
     """Test a DMS archive."""
     check_archive_ext(archive)
     cmdlist = [cmd, 't']
-    if password:
-        cmdlist.extend(['-p', password])
+    _maybe_add_password(cmdlist, password)
     cmdlist.append(archive)
     return cmdlist