print statement delays printing when followed by comma

Question

In Python 2.7, if I use print statement followed by comma as the following:

print('Generation ...'),
X, y = generate_dataset(num_samples)
print('Done!')

The first print print('Generation ...'), will NOT show up in the terminal until X, y = generate_dataset(num_samples) is finished! How can I force the print to immediately step by step with the existence of comma?

you cannot do it, if you keep comma print statement will wait until x,y are evaluated and only then print statement can show the result — Tilak Putta, Dec 06 '17 at 18:57
https://stackoverflow.com/questions/230751/how-to-flush-output-of-python-print You'll probably have to manually flush output. Comma is not exactly relevant here since print is a side effect that doesn't need to wait for evaluation results. — Haochen Wu, Dec 06 '17 at 19:10
`print "aaa",inf_loop()` does print to screen before I hit Ctrl+C in Jupyter notebook and `print "aa", sys.stdout.flush(), inf_loop()` does print to screen in interactive python shell. — Haochen Wu, Dec 06 '17 at 19:12

score 0 · Answer 1 · answered Dec 06 '17 at 19:47

0

import sys

print "I'm going to do something that takes a long time...",
sys.stdout.flush()
really_time_consuming_function()
print "done!"

answered Dec 06 '17 at 19:47

PaulMcG

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score 0 · Answer 2 · answered Dec 06 '17 at 19:58

0

You can also run the python interpreter with the -u flag if you don't want to handle this in code.

answered Dec 06 '17 at 19:58

Chris Johnson

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print statement delays printing when followed by comma

2 Answers2