poutput() can not print a zero.

[kotfu]

Say you built an app which subclasses cmd2. Say you wanted to have an 'exit_code' command in your app which printed out the exit code of the last command processed. Say you wanted to output an exit code of zero, using the poutput() function. It won't print it.

Here's the poutput() function:

cmd2/cmd2.py

Lines 588 to 599 in 5d5675b

	if msg:
	try:
	msg_str = '{}'.format(msg)
	self.stdout.write(msg_str)
	if not msg_str.endswith(end):
	self.stdout.write(end)
	except BROKEN_PIPE_ERROR:
	# This occurs if a command's output is being piped to another process and that process closes before the
	# command is finished. We intentionally don't print a warning message here since we know that stdout
	# will be restored by the _restore_output() method. If you would like your application to print a
	# warning message, then override this method.
	pass

If msg evaluates to false, then nothing is output. An empty string, and a zero both evaluate to false.

Recommended fix:

if msg is not None:

[tleonhardt]

@kotfu

The original intent of the if msg check was to make sure that msg is not an empty string and I was making use of the Falsiness of empty strings. My underlying assumption was that msg was either of type str or something automatically convertible to str using .format(). But I didn't think about non-string types which would be Falsy such as integer zero.

So I would recommend slightly modifying your recommended fix to something like the following:

if msg is not None and msg != '':

[tleonhardt]

@kotfu
I'll go ahead and submit a PR for this shortly unless you are already working on it.

[kotfu]

Makes sense. The check for None and an empty string is better.