CODEWITHSUNDEEP
pythonloopsmodulo
Colin Barmorian
Colin Barmorian

Reputation: 3

Do you know why my loop + modulo (%) skips numbers in python

I am trying to do an update every 20 steps but it skips some numbers I don't understand why

time=np.linspace(0.1,100,1000)    

for t in time:
    if t % 2 ==0.0:
        print(t, 'ms')

Thank you

Upvotes: 0

Views: 89

Answers (1)

Code Pope
Code Pope

Reputation: 5459

This due to the fact that linespace does not achieve exact values like 18.0 or 20.0. Due to floating point calculation there is a small epsilon. You can change your code like the following, then you will hit all the numbers:

time=np.linspace(0.1,100,1000)    
epsilon = 0.0001
for t in time:
    if t % 2 < epsilon:
        print(t, 'ms')

Another way is to just print out every 20 step (the first print would be but after 19):

time=np.linspace(0.1,100,1000)    
epsilon = 0.0001
for i,t in enumerate(time):
    if (i -19) % 20 ==0:
        print(t, 'ms')

Output:

2.0 ms
4.0 ms
6.0 ms
8.0 ms
10.0 ms
12.0 ms
14.0 ms
16.0 ms
....

Upvotes: 1

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