Python loop add up a float, the result is not right

Question

I was using a simple for loop to add numbers but I found a strange result when adding float.

Can you explain why I have the following output ?

1.1
1.2000000000000002
1.3000000000000003
1.4000000000000004
1.5000000000000004
1.6000000000000005
1.7000000000000006
1.8000000000000007
1.9000000000000008
2.000000000000001
2.100000000000001
2.200000000000001
2.300000000000001
2.4000000000000012
2.5000000000000013
2.6000000000000014
2.7000000000000015
2.8000000000000016
2.9000000000000017
3.0000000000000018
3.100000000000002
3.200000000000002
3.300000000000002
3.400000000000002
3.500000000000002
3.6000000000000023
3.7000000000000024
3.8000000000000025
3.9000000000000026

This is based on Anaconda Spyder

a = 1

for i in range(1,30):
    a = a+0.1
    print(a)

This is well known and due to the way the floats are stored – BlueSheepToken Jul 23 '19 at 09:55 — BlueSheepToken, Jul 23 '19 at 09:55

score 1 · Answer 1 · answered Jul 23 '19 at 10:26

1

It's a known limitation of floating point arithmetic, computers cannot store infinitely precise floating point numbers. See python docs.

answered Jul 23 '19 at 10:26

asikorski

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Python loop add up a float, the result is not right

1 Answers1