Go: package main

import (
	"bufio"
	"fmt"
	"io"
	"math"
	"os"
	"strconv"
	"strings"

)


func main() {
	solve(os.Stdin, os.Stdout)
}

type ReaderEx struct {
	baseScanner *bufio.Scanner
	words       []string
	nextWordIdx func() int
	initWordIdx func(int)
}

func NewScannerEx(stdin io.Reader) *ReaderEx {
	var this ReaderEx
	var idx int
	var wordsCnt int
	this.baseScanner = bufio.NewScanner(stdin)
	this.baseScanner.Buffer(make([]byte, 0), 1E+11)
	this.nextWordIdx = func() int {
		cur := idx
		idx = (idx + 1) % wordsCnt
		return cur
	}
	this.initWordIdx = func(wc int) {
		idx = 0
		wordsCnt = wc
	}
	return &this
}

func (me *ReaderEx) Scan(doSplit bool) (isScanned bool) {
	isScanned = me.baseScanner.Scan()
	if doSplit {
		me.words = strings.Fields(me.baseScanner.Text())
	} else {
		me.words = []string{me.baseScanner.Text()}
	}
	me.initWordIdx(len(me.words))
	return
}

func (me *ReaderEx) nextBytes() []byte {
	return []byte(me.words[me.nextWordIdx()])
}
func (me *ReaderEx) nextString() string {
	return me.words[me.nextWordIdx()]
}

type StringArray []string

func (me *ReaderEx) nextStringArray() StringArray {
	return me.words[me.nextWordIdx():]
}

func (me StringArray) toStrings() []string {
	return me
}

func (me StringArray) toInts() []int {
	strValues := me.toStrings()
	values := make([]int, len(strValues))
	for i, v := range strValues {
		n, err := strconv.Atoi(v)
		if err != nil {
			panic(err)
		}
		values[i] = n
	}
	return values
}
func (me *ReaderEx) nextInt() int {
	n, err := strconv.Atoi(me.words[me.nextWordIdx()])

	defer func() {
		if err != nil {
			panic(fmt.Sprintf("getInt(%d)", n))
		}
	}()
	return n
}

func pow(x, y, mod int) (ans int) {

	ans = 1
	for bit := 1 << uint(math.Floor(math.Log2(float64(y)))); ; bit >>= 1 {
		if y&bit != 0 {
			ans *= x
			if mod > 0 {
				ans %= mod
			}
		}
		if bit <= 1 {
			return
		}
		ans *= ans
		if mod > 0 {
			ans %= mod
		}
	}
}

type factType struct {
	prime int
	count int
}

func fact(n int) (facts []*factType) {

	for i := 2; i*i <= n; i++ {
		if n%i == 0 {
			fa := factType{prime: i}
			for n%fa.prime == 0 {
				n /= fa.prime
				fa.count++
			}
			facts = append(facts, &fa)
		}
	}
	if n > 1 {
		facts = append(facts, &factType{prime: n, count: 1})
	}
	return facts
}
func dec2bin(n int) (ret []bool) {
	for bit := 1 << uint(math.Floor(math.Log2(float64(n)))); ; bit >>= 1 {
		ret = append(ret, n&bit != 0)

		if bit <= 1 {
			return
		}
	}

}

func abs(v int) int {
	if v < 0 {
		v = -v
	}
	return v
}

func b2i(b bool) (i int) {
	if b {
		i = 1
	} else {
		i = 0
	}
	return
}

func solve(stdin io.Reader, stdout io.Writer) {

	r := NewScannerEx(stdin)
	r.Scan(true)
	n := r.nextInt()

	type Vec struct {
		x, y float64
	}
	vec := func(a, b Vec) Vec { return Vec{b.x - a.x, b.y - a.y} }
	unv := func(a Vec) Vec { return Vec{-a.y, a.x} }
	cdot := func(a, b Vec) float64 { return a.x*b.x + a.y*b.y }
	times := func(t float64, a Vec) Vec { return Vec{t * a.x, t * a.y} }
	add := func(a, b Vec) Vec { return Vec{a.x + b.x, a.y + b.y} }
	for i := 0; i < n; i++ {

		r.Scan(true)
		nextFloat64 := func() (ret float64) { fmt.Sscanf(r.nextString(), "%f", &ret); return }
		a1, a2, a3 := Vec{nextFloat64(), nextFloat64()}, Vec{nextFloat64(), nextFloat64()}, Vec{nextFloat64(), nextFloat64()}
		unv23 := unv(vec(a2, a3))
		v12 := vec(a1, a2)
		v31 := vec(a3, a1)
		s := cdot(v12, v31) / 2 / cdot(v12, unv23)
		c := add(times(.5, add(a2, a3)), times(s, unv23))
		v1c := vec(a1, c)
		fmt.Fprintf(stdout, "%.3f %.3f %.3f\n", c.x, c.y, math.Sqrt(v1c.x*v1c.x+v1c.y*v1c.y))
	}
}

Python: for _ in[0]*int(input()):
 a,b,c,d,e,f=map(float,input().split())
 s,t,u=a*a+b*b,c*c+d*d,e*e+f*f
 x=(s*(d-f)+t*(f-b)+u*(b-d))/2/(a*(d-f)+c*(f-b)+e*(b-d))
 y=(s*(c-e)+t*(e-a)+u*(a-c))/2/(b*(c-e)+d*(e-a)+f*(a-c))
 print('%.3f %.3f %.3f'%(x,y,((x-a)**2+(y-b)**2)**.5))

Python: from math import acos
from math import sin

def ang(ax, ay, ox, oy, bx, by):
    oax, oay = ax - ox, ay - oy
    obx, oby = bx - ox, by - oy
    r1, r2 = oax ** 2 + oay ** 2, obx ** 2 + oby ** 2
    return acos((oax * obx + oay * oby) / (r1 * r2) ** 0.5)

def circumcircle(x1, y1, x2, y2, x3, y3):
    s2A = sin(2 * ang(x3, y3, x1, y1, x2, y2))
    s2B = sin(2 * ang(x1, y1, x2, y2, x3, y3))
    s2C = sin(2 * ang(x2, y2, x3, y3, x1, y1))
    px = (s2A * x1 + s2B * x2 + s2C * x3) / (s2A + s2B + s2C) + 0.
    py = (s2A * y1 + s2B * y2 + s2C * y3) / (s2A + s2B + s2C) + 0.
    r = (((x2 - x3) ** 2 + (y2 - y3) ** 2) ** 0.5) / (2 * sin(ang(x2, y2, x1, y1, x3, y3))) + 0.
    return px, py, r

n = int(input())
for i in range(n):
    print("{0[0]:.3f} {0[1]:.3f} {0[2]:.3f}".format(
          circumcircle(*tuple(map(float, input().split())))))

Python: # coding: utf-8
# Here your code !
import math
 
num = int(input())
for i in range(num):
    x1,y1,x2,y2,x3,y3 = map(float,input().split())
    a1 = 2*(x2-x1)
    b1 = 2*(y2-y1)
    c1 = (x1*x1 - x2*x2 + y1*y1 - y2*y2)
    a2 = 2*(x3-x1)
    b2 = 2*(y3-y1)
    c2 = (x1*x1 - x3*x3 + y1*y1 - y3*y3)
 
    p1 = (b1*c2 - b2*c1) / (a1*b2 - a2*b1)
    p2 = (c1*a2 - c2*a1) / (a1*b2 - a2*b1)
    r = math.hypot(x1-p1, y1-p2)
    temp = [p1,p2,r]
    ans = map(lambda x:round(x,3),temp)
    print("%03.3f %03.3f %03.3f"%(temp[0],temp[1],temp[2]))

Python: def pp(x):
    if x==0:
        x=0
    return "{0:.3f}".format(round(x,3))


n=int(input())
for i in range(n):
    x1,y1,x2,y2,x3,y3=map(float, input().split())

    a=2*(x2-x1)
    b=2*(y2-y1)
    c=( x2**2 + y2**2 ) - ( x1**2 + y1**2 )
    d=2*(x3-x1)
    e=2*(y3-y1)
    f=( x3**2 + y3**2 ) - ( x1**2 + y1**2 )
    x=(c*e-b*f)/(a*e-b*d)
    y=(a*f-c*d)/(a*e-b*d)
    r=( (x-x1)**2 + (y-y1)**2 )**0.5
 
    print(pp(x), pp(y), pp(r))