问题
I've been learning programming in python for the last two weeks and it's going great so far. But now I'm stuck and can't seem to find an answer. I found a really weird behaviour of a while loop, I just can't wrap my head around.
x=0
step_size=0.2
while x<2:
print x
x+=step_size
This code prints:
0
0.2
0.4
...
1.8
2.0
2.0 should not be printed, right? When x becomes 2.0 the statement "x<2" is false, therefore the loop should exit and never print 2.0.
And now for the really weird part: it works with other numbers. Step_size=0.4 prints up to 1.6, step_size=0.1 up to 1.9. Using "x<1" as a statement and step_size=0.2 also works.
What am I missing?
Best regards, Leo
Edit: I'm using python 2.7.5 and the default Idle Editior v2.7.5
回答1:
It's floating point arythmetic. Output in console for python 3.6
0
0.2
0.4
0.6000000000000001
0.8
1.0
1.2
1.4
1.5999999999999999
1.7999999999999998
1.9999999999999998
来源：https://stackoverflow.com/questions/53208032/while-loop-not-counting-correctly