1

Maybe a silly question, I am trying to print numbers in a loop in such a way that they are multiples of 10. This is very easy as long as the timestep in the loop is multiple of 10. This is how I do it:

time = 0.
timestep = 2.
while time <= 100.:
    if int(round(time)) % 10 == 0:
        print time
    time += timestep

which gives me an output of: 

0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0

And if I use a timestep = 1, I get a similar output. My problem is that now my timestep is given as a function of another variable, and is a float with many decimals. For one case, for instance, the timestep turns out to be 1.31784024239, and if I try to do a similar loop, the numbers I get are not that uniform anymore. For example, I get:

0.0 
19.7676036358 
30.310325575 
39.5352072717
50.0779292108
69.8455328467
80.3882547858
89.6131364825

My question is if there is any trick so that my output is printed uniformly - every, let's say, 10 days? it doesn't have to be exactly ten, but I would like to have a point, for example, between 0 and 19 (around 10) and another one around 60, since theres a jump from 50.07 to 69.84.

I don't know if it is possible, but any ideas will really be helpful as many of my timesteps are floats with many decimals.

ekhumoro
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user3412058
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  • What should happen if `timestep` is more than 3, so it skips from 9 to 12 without going near 10? – Barmar Mar 21 '18 at 21:22
  • I don't have timesteps larger than 2, but in that case I wouldn't mind if the numbers are written every 9 days instead. As long as the numbers are "integers" I think I can just make them multiples of other numbers different from 10. My problem right now is that all my timesteps have many decimals. – user3412058 Mar 21 '18 at 21:31
  • You don't need lots of decimals for this problem, it occurs with `1.32` because `time` jumps from `9.24` to `10.56`. Which of these should be printed? – Barmar Mar 21 '18 at 21:34
  • either will be fine. – user3412058 Mar 21 '18 at 21:37

2 Answers2

3

Here's a simple solution that finds the steps that are nearest to a given series of multiples:

def stepper(timestep, limit=100.0, multiple=10.0):
    current = multiples = 0.0
    while current <= limit:
        step = current + timestep
        if step >= multiples:
            if multiples - current > step - multiples:
                yield step
            else:
                yield current
            multiples += multiple
        current = step

for step in stepper(1.31784024239):
    print step

Output:

0.0
10.5427219391
19.7676036358
30.310325575
39.5352072717
50.0779292108
60.6206511499
69.8455328467
80.3882547858
89.6131364825
100.155858422
ekhumoro
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1

Remember the last time you printed a line, and print another line as soon as the decade changes:

time = 0.
lasttime = -1.
timestep = 3.
while time <= 100.:
    if time // 10 != lasttime // 10:
        print time
        lasttime = time
    time += timestep

Result:

$ python x.py 
0.0
12.0
21.0
30.0
42.0
51.0
60.0
72.0
81.0
90.0
Robᵩ
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  • Hmm. It will always give a point *beyond* the threshold, not necessarily the closest point. – wim Mar 21 '18 at 21:04