Python: Showing percentage of operation

Question

I'm doing some stuff on several lines of data. This takes a long time, and I would like to show the percentage of progress.

So I have the following code:

for y in range(0, height):
    if (y * 100 / height).is_integer():
        print("... ", int(y * 100 / height), "%")

height is the number of lines that need to be processed.

However, somehow this code doesn't print the correct percentages. If height is 100 it works fine. For 4050 it prints every 2 percentages (0%, 2%, 4%, ...). For 2025 it prints every 4 percentages...

Why does this happen? And how can I fix it?

[Why not use a ready-made library?](https://pypi.python.org/pypi/tqdm) — Christian Dean, Dec 15 '16 at 00:29
If you simulate the first few iterations in a repl you'll easily see why -- going from the `i`th iteration to the `i+1`th iteration might easily step from, say, 0.8% complete to 1.2% complete, neither of which are integers. — Cameron, Dec 15 '16 at 00:31
Hmm, that looks very nice. Still, would love to know the answer :P — The Oddler, Dec 15 '16 at 00:31
@Cameron Damn yes, that makes so much sense! So stupid I didn't realise this myself. — The Oddler, Dec 15 '16 at 00:32
why not just using a counter divided by the total of lines? I didn't understand very well what you meant on this if statement — Jeanderson Candido, Dec 15 '16 at 00:33

score 2 · Accepted Answer · answered Dec 15 '16 at 00:36

Not exactly proud of my code, but anyway:

last = -1 # Start it as -1, so that it still prints 0%.
for y in range(0, height):
    work = int(y * 100 / height) # I assigned the percentage to a variable for neatness.
    if work != last: # so it doesn't print the same percent over and over.
        print("... ", work, "%")
    last = work # Reset 'last'.

This may/may not be completely accurate. But it works

The reason you had your problem is from the is_integer() was only true on specific values.

Hope this helps!

Python: Showing percentage of operation

1 Answers1