(This post was originally published in @pythonetc telegram channel)

`round`

function rounds a number to a given precision in decimal digits.

```
>>> round(1.2)
1
>>> round(1.8)
2
>>> round(1.228, 1)
1.2
```

Also you can set up negative precision:

```
>>> round(413.77, -1)
410.0
>>> round(413.77, -2)
400.0
```

`round`

returns value of input number’s type:

```
>>> type(round(2, 1))
<class 'int'>
>>> type(round(2.0, 1))
<class 'float'>
>>> type(round(Decimal(2), 1))
<class 'decimal.Decimal'>
>>> type(round(Fraction(2), 1))
<class 'fractions.Fraction'>
```

For your own classes you can define `round`

processing with `__round__`

method:

```
>>> class Number(int):
... def __round__(self, p=-1000):
... return p
...
>>> round(Number(2))
-1000
>>> round(Number(2), -2)
-2
```

Values are rounded to the closest multiple of `10 ** (-precision)`

. For example, for `precision=1`

value will be rounded to multiple of 0.1 (`round(0.63, 1)`

returns 0.6). If two multiples are equally close, rounding is done toward the even choice:

```
>>> round(0.5)
0
>>> round(1.5)
2
```

Sometimes rounding of floats can be a little bit surprising:

```
>>> round(2.85, 1)
2.9
```

This is because most decimal fractions can’t be represented exactly as a float:

```
>>> format(2.85, '.64f')
'2.8500000000000000888178419700125232338905334472656250000000000000'
```

If you want to round half up you can use `decimal.Decimal`

:

```
>>> from decimal import Decimal, ROUND_HALF_UP
>>> Decimal(1.5).quantize(0, ROUND_HALF_UP)
Decimal('2')
>>> Decimal(2.85).quantize(Decimal('1.0'), ROUND_HALF_UP)
Decimal('2.9')
>>> Decimal(2.84).quantize(Decimal('1.0'), ROUND_HALF_UP)
Decimal('2.8')
```