Cameron Simpson wrote:
> On 03Jan2017 00:14, Dennis Lee Bieber <wlfr...@ix.netcom.com> wrote:
>>On Tue, 3 Jan 2017 11:33:15 +1100, Cameron Simpson <c...@zip.com.au>
>>declaimed the following:
>>>I'm using cmd.Cmd to write a little FTP-like command line to interface to
>>>a storage system of mine and encountering weird behaviour. When I enter a
>>>command the next prompt appears _before_ the associated operation runs,
>>>or so it appears.
>><SNIP>
>>>Has anyone seen this kind of thing before?
>>
>>Haven't used the module but there is something I find intriguing in the
>>help system
>>-=-=-=-=-
>> Cmd.precmd(line)
>> Hook method executed just before the command line is interpreted, but
>>after the input prompt is generated and issued.
>>-=-=-=-=-
>>"... AFTER the input prompt is ... issued"
>>
>>I don't know, but that sure sounds to me like the cmd object tends to
>>process one line behind... Though that behavior is not shown in the turtle
>>example in the help system.
>
> Hmm. Interesting. I had read that text to imply (based on what I imagined
> _should_ happen) that the flow of control went:
>
> cmdloop:
> issue prompt>
> line=input() # or readline
> line=precmd(line)
> stop=onecmd(line) # which calls do_blah...
> stop=postcmd(stop,line)
> if stop:
> break
>
> but your reading of it suggests that this is possible:
>
> issue prompt>
> cmdloop:
> line=input() # or readline
> issue prompt>
> line=precmd(line)
> stop=onecmd(line) # which calls do_blah...
> stop=postcmd(stop,line)
> if stop:
> break
>
> The text for Cmd.cmdloop starts with this:
>
> Repeatedly issue a prompt, accept input, parse an initial prefix off the
> received input, and dispatch to action methods, passing them the
> remainder of the line as argument.
>
> which argues for the former, and was what I naively expected.
>
> I guess I'd better dig out the source; I dislike going that far, not
> merely out of laziness, but also because the source is not the spec.
>
> Thanks for the suggestion,
> Cameron Simpson <c...@zip.com.au>
I don't believe Dennis' reading of the docs is correct, and the relevant
part of the source (Python 3.4) does not show anything to support it:
while not stop:
if self.cmdqueue:
line = self.cmdqueue.pop(0)
else:
if self.use_rawinput:
try:
line = input(self.prompt)
except EOFError:
line = 'EOF'
else:
self.stdout.write(self.prompt)
self.stdout.flush()
line = self.stdin.readline()
if not len(line):
line = 'EOF'
else:
line = line.rstrip('\r\n')
line = self.precmd(line)
stop = self.onecmd(line)
stop = self.postcmd(stop, line)
self.postloop()
Is there something asynchronous in your command? Perhaps you can post a
minimal runnable example that shows the odd behaviour.
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