Floating point precision while using Python's max()

Question

Why so?

>>> max(2, 2.01)
2.0099999999999998

Because that's how floating point numbers work: http://download.oracle.com/docs/cd/E19957-01/806-3568/ncg_goldberg.html — duffymo, Apr 18 '11 at 10:12
Take a look at [float-str-float wierdness](http://stackoverflow.com/questions/1778368/python-float-str-float-weirdness) on StackOverflow — Mike Pennington, Apr 18 '11 at 10:13

Stephen Canon · Accepted Answer · 2011-04-18T17:43:55.090

The number 2.01 represented in binary is:

b10.00000010100011111100001010001111110000101000111111000010100011111100...

The computer uses only a finite number of digits to store floating-point values, but the binary representation of 2.01 requires infinitely many digits; as a result, it is rounded to the closest representable value:

b10.000000101000111111000010100011111100001010001111110

Expressed in decimal, this number is exactly:

2.0099999999999997868371792719699442386627197265625

When you print it out, it is rounded a second time to seventeen decimal digits, giving:

2.0099999999999998

score 3 · Answer 2 · edited Apr 18 '11 at 10:31

3

Floating point numbers do not encode exact values, but approximations. The result is essentially the next nearest floating point number to the real number you entered.

http://docs.python.org/tutorial/floatingpoint.html

edited Apr 18 '11 at 10:31

colechristensen

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answered Apr 18 '11 at 10:10

Ocaso Protal

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score 2 · Answer 3 · answered Apr 18 '11 at 10:12

2

because:

>>> 2.01
2.0099999999999998

it's the way floating point numbers are stored

answered Apr 18 '11 at 10:12

dting

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score 0 · Answer 4 · answered Apr 18 '11 at 10:12

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Floating point roundoff. Its trying to say 2.01 but can't express it exactly as a floating point number so its doing the best it can.

answered Apr 18 '11 at 10:12

verstapp

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Floating point precision while using Python's max()

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