.write() clashes with nested bars on python 3.6

[staffanm]

Starting with the example code given for nested progress bars, I've tried the following:

from tqdm import trange, tqdm
from time import sleep

for i in trange(10, desc='1st loop'):
    tqdm.write("%s" % i)
    for j in trange(5, desc='2nd loop', leave=False):
	tqdm.write("%s, %s" % (i, j))
        for k in trange(100, desc='3nd loop'):
            tqdm.write("%s, %s, %s" % (i,j,k))
            sleep(0.01)

Under python 2.7 this works as expected, the log messages are written above the three nested progress bars at the bottom of the console.

On python 3.6, the log messages appear to overwrite the progress bars, which are rapidly scrolled off-screen (by new log messages) as soon as they are updated.

Maybe this is related to #348 -- applying the patch suggested in #331 does not fix the problem, however.

This is on MacOS Sierra, using the stock Terminal app.

[duckythescientist]

It's a Python 3.5 issue as well. Even just the presence of a second bar will keep writes from being shown. Here is my minimized example:

from time import sleep
from tqdm import tqdm

def two_bars_with_surrounding_write():
    tqdm.write("starting")
    sleep(1)

    a = tqdm(total=10)
    b = tqdm(total=100)
    sleep(1)

    a.update()
    b.update()

    tqdm.write("finished")
    sleep(1)
    tqdm.write("finished again")
    sleep(1)

two_bars_with_surrounding_write()
"""starting text shows but neither finished text shows"""

Ubuntu 16.04 with Guake or stock terminal.

[staffanm]

@duckythescientist Could you try the small change suggested in #399 and see if it fixes your problem? It seems to do that in my environment.

[duckythescientist]

@staffanm That fixes the problem when I have two progress bars and doing writes, but when I have one bar then do a write, the write works, but the bar disappears.

However, if I always self.fp.flush() instead of only when n is truthy, that fixes both problems.

[staffanm]

Good catch @duckythescientist -- I've updated the PR accordingly