Only pass strings to shlex

Avoid passing None, which causes it to read from stdin.

Closes gh-433

2 files changed, 7 insertions, 1 deletions

diff --git a/pexpect/popen_spawn.py b/pexpect/popen_spawn.py
index 600ac92..c9d4738 100644
--- a/pexpect/popen_spawn.py
+++ b/pexpect/popen_spawn.py
@@ -15,6 +15,7 @@ except ImportError:
 
 from .spawnbase import SpawnBase, PY3
 from .exceptions import EOF
+from .utils import string_types
 
 class PopenSpawn(SpawnBase):
     if PY3:
@@ -39,7 +40,7 @@ class PopenSpawn(SpawnBase):
             kwargs['startupinfo'] = startupinfo
             kwargs['creationflags'] = subprocess.CREATE_NEW_PROCESS_GROUP
 
-        if not isinstance(cmd, (list, tuple)):
+        if isinstance(cmd, string_types):
             cmd = shlex.split(cmd)
 
         self.proc = subprocess.Popen(cmd, **kwargs)
diff --git a/pexpect/utils.py b/pexpect/utils.py
index ae0fe9d..bafc280 100644
--- a/pexpect/utils.py
+++ b/pexpect/utils.py
@@ -11,6 +11,11 @@ except NameError:
     # Alias Python2 exception to Python3
     InterruptedError = select.error
 
+if sys.version_info[0] >= 3:
+    string_types = (str,)
+else:
+    string_types = (unicode, str)
+
 
 def is_executable_file(path):
     """Checks that path is an executable regular file, or a symlink towards one.