Brett Cannon's dummy_thread and dummy_threading modules (SF patch

622537), with some nitpicking editorial changes.

Lib/dummy_thread.py

@@ -0,0 +1,116 @@
+"""Drop-in replacement for the thread module.
+
+Meant to be used as a brain-dead substitute so that threaded code does
+not need to be rewritten for when the thread module is not present.
+
+Suggested usage is::
+    
+    try:
+        import thread
+    except ImportError:
+        import dummy_thread as thread
+
+"""
+__author__ = "Brett Cannon"
+__email__ = "brett@python.org"
+
+# Exports only things specified by thread documentation
+# (skipping obsolete synonyms allocate(), start_new(), exit_thread())
+__all__ = ['error', 'start_new_thread', 'exit', 'get_ident', 'allocate_lock',
+           'LockType']
+
+import traceback as _traceback
+
+class error(Exception):
+    """Dummy implementation of thread.error."""
+
+    def __init__(self, *args):
+        self.args = args
+
+def start_new_thread(function, args, kwargs={}):
+    """Dummy implementation of thread.start_new_thread().
+
+    Compatibility is maintained by making sure that ``args`` is a
+    tuple and ``kwargs`` is a dictionary.  If an exception is raised
+    and it is SystemExit (which can be done by thread.exit()) it is
+    caught and nothing is done; all other exceptions are printed out
+    by using traceback.print_exc().
+
+    """
+    if type(args) != type(tuple()):
+        raise TypeError("2nd arg must be a tuple")
+    if type(kwargs) != type(dict()):
+        raise TypeError("3rd arg must be a dict")
+    try:
+        function(*args, **kwargs)
+    except SystemExit:
+        pass
+    except:
+        _traceback.print_exc()
+
+def exit():
+    """Dummy implementation of thread.exit()."""
+    raise SystemExit
+
+def get_ident():
+    """Dummy implementation of thread.get_ident().
+
+    Since this module should only be used when threadmodule is not
+    available, it is safe to assume that the current process is the
+    only thread.  Thus a constant can be safely returned.
+    """
+    return -1
+
+def allocate_lock():
+    """Dummy implementation of thread.allocate_lock()."""
+    return LockType()
+
+class LockType(object):
+    """Class implementing dummy implementation of thread.LockType.
+    
+    Compatibility is maintained by maintaining self.locked_status
+    which is a boolean that stores the state of the lock.  Pickling of
+    the lock, though, should not be done since if the thread module is
+    then used with an unpickled ``lock()`` from here problems could
+    occur from this class not having atomic methods.
+
+    """
+
+    def __init__(self):
+        self.locked_status = False
+    
+    def acquire(self, waitflag=None):
+        """Dummy implementation of acquire().
+
+        For blocking calls, self.locked_status is automatically set to
+        True and returned appropriately based on value of
+        ``waitflag``.  If it is non-blocking, then the value is
+        actually checked and not set if it is already acquired.  This
+        is all done so that threading.Condition's assert statements
+        aren't triggered and throw a little fit.
+
+        """
+        if waitflag is None:
+            self.locked_status = True
+            return None 
+        elif not waitflag:
+            if not self.locked_status:
+                self.locked_status = True
+                return True
+            else:
+                return False
+        else:
+            self.locked_status = True
+            return True 
+
+    def release(self):
+        """Release the dummy lock."""
+        # XXX Perhaps shouldn't actually bother to test?  Could lead
+        #     to problems for complex, threaded code.
+        if not self.locked_status:
+            raise error
+        self.locked_status = False
+        return True
+
+    def locked(self):
+        return self.locked_status