qtconsole Out value prints before the print statements that precede it #780

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jdmarch opened this Issue Sep 11, 2011 · 1 comment

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jdmarch commented Sep 11, 2011

In [1]: def ff():
...: print '(computing)'
...: return 123

In [2]: ff()
Out[2]: 123(computing)

This does not occur in standard ipython.
Only tested on OSX.

minrk added a commit to minrk/ipython that referenced this issue Sep 12, 2011

flush stdout/stderr on displayhook
This helps stream output arrive before pyout.

closes gh-780
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minrk Sep 12, 2011

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I see the same thing. I swear we keep fixing this, and it keeps coming back.

It's not necessarily incorrect that the 123 is coming before the printed message, because when print text actually gets drawn is controlled by sys.stdout.flush, so unless you are calling flush yourself, such things are not technically reliable (though they tend to be consistent within a given environment). What is definitely incorrect is that stdout content should never show up on the same line as pyout.

If we add sys.stdout.flush() to the zmq.displayhook prior to send, then it will behave as you are expecting, so we should probably do that (see PR #782).

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minrk commented Sep 12, 2011

I see the same thing. I swear we keep fixing this, and it keeps coming back.

It's not necessarily incorrect that the 123 is coming before the printed message, because when print text actually gets drawn is controlled by sys.stdout.flush, so unless you are calling flush yourself, such things are not technically reliable (though they tend to be consistent within a given environment). What is definitely incorrect is that stdout content should never show up on the same line as pyout.

If we add sys.stdout.flush() to the zmq.displayhook prior to send, then it will behave as you are expecting, so we should probably do that (see PR #782).

@minrk minrk closed this in a677855 Sep 12, 2011

mattvonrocketstein pushed a commit to mattvonrocketstein/ipython that referenced this issue Nov 3, 2014

flush stdout/stderr on displayhook
This helps stream output arrive before pyout.

closes gh-780
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