Python built-in function (--round)

English documents:

round( number[, ndigits]) Return The floating point value number rounded to ndigits digits after the decimal point. If ndigits is omitted, it returns the nearest integer to its input. Delegates tonumber.__round__(ndigits).For the built-in types supportinground(), values is rounded to the closest multiple of ten to the power minus Ndigi TS; If the multiples is equally close, rounding is do toward the even choice (so, for example, both and wasround(0.5)round(-0.5)0, andround(1.5)is2). The return value is a integer if called with one argument, otherwise of the same type as number. Note:

round()the behavior of floats can be surprising:for example,round(2.675, 2)gives instead of the2.67expected2.68. This was not a bug:it's a result of the fact that most decimal fractions can ' t be represented exactly as a float. See floating point arithmetic:issues and limitations for more information.

Description

1. The round function is used for rounding the floating-point numbers, reserving several decimals, and controlling them with the incoming ndigits parameter.

>>> round(1.1314926,1)
1.1
>>> round(1.1314926,5)
1.13149

2. The ndigits parameter is an optional parameter that, when not passed in, is rounded by the default of 0 decimal places, and returns an integer.

>>> round (1.1314926)1

3. The Ndigits parameter is passed in 0 o'clock, although 0 decimal places are rounded up as if the Ndigits parameter is not passed in, but the returned value is floating-point.

>>> round (1.1314926, 0)1.0

4. The ndigits parameter is less than 0 o'clock, rounding the integer part, the ndigits parameter controls the rounding of the number of the integer part of the floating-point number, the fractional part is cleared 0, and the return type is a floating-point number. Returns 0.0 if the integer portion of the incoming floating-point number is less than the absolute value of the Ndigits parameter.

>>> round(11314.926,-1)
11310.0
>>> round(11314.926,-3)
11000.0
>>> round(11314.926,-4)
10000.0
>>> round(11314.926,-5)
0.0

5. Round rounding is followed near the 0 principle, so-0.5 and 0.5 are rounded 0 bits, and return is 0.

>>> round(0.5)
0
>>> round(-0.5)
0

6. There is a trap for rounding floating-point numbers, and some rounding results are not as expected, asround(2.675, 2)the results are2.67rather than expected2.68，This is not a bug, but because floating-point numbers are stored with a limited number of digits, there is a certain error between the actual stored value and the displayed value.

>>> round (2.675, 2)2.67

7. You can also perform round operations on integers, and return values are also shaped.

>>> round(134567)
134567
>>> round(134567,0)
134567
>>> round(134567,1)
134567
>>> round(134567,2)
134567
>>> round(134567,-2)
134600
>>> round(134567,-6)
0

Python built-in function (--round)