Inspired by Tim Peters' 1.14->1.15 checkin to asynchat

Moshe Zadka · Moshe Zadka · commit 097cf85daec7 · 2001-04-11T08:06:02.000Z
Quoting orignal message: ''' Fix from the Madusa mailing list: http://groups.yahoo.com/group/medusa/message/333 It's clear that Medusa should not be checking for an empty buffer via "buf is ''". The patch merely changes "is" to "==". However, there's a mystery here all the same: Python attempts to store null strings uniquely, so it's unclear why "buf is ''" ever returned false when buf actually was empty. *Some* string operations produce non-unique null strings, e.g. '''
diff --git a/Lib/asynchat.py b/Lib/asynchat.py
@@ -166,7 +166,7 @@ def writable (self):
 		# return len(self.ac_out_buffer) or len(self.producer_fifo) or (not self.connected)
 		# this is about twice as fast, though not as clear.
 		return not (
-			(self.ac_out_buffer is '') and
+			(self.ac_out_buffer == '') and
 			self.producer_fifo.is_empty() and
 			self.connected
 			)

Original file line number	Diff line number	Diff line change
`@@ -166,7 +166,7 @@ def writable (self):`
`166`	`166`	`# return len(self.ac_out_buffer) or len(self.producer_fifo) or (not self.connected)`
`167`	`167`	`# this is about twice as fast, though not as clear.`
`168`	`168`	`return not (`
`169`		`- (self.ac_out_buffer is '') and`
	`169`	`+ (self.ac_out_buffer == '') and`
`170`	`170`	`self.producer_fifo.is_empty() and`
`171`	`171`	`self.connected`
`172`	`172`	`)`