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: n = int(input())
for i in range(n):
    x1, y1, x2, y2, x3, y3 = list(map(float, input().split()))
    a = complex(x1, y1)
    b = complex(x2, y2)
    c = complex(x3, y3)
    a -= c
    b -= c
    z0 = abs(a)**2 * b - abs(b)**2 * a
    z0 /= a.conjugate() * b - a * b.conjugate()
    z = z0 + c
    zx = "{0:.3f}".format(z.real)
    zy = "{0:.3f}".format(z.imag)
    r  = "{0:.3f}".format(abs(z0))
    print(zx, zy, r)

Python: #!/usr/bin/env python
#-*- coding:utf-8 -*-
 
import sys
import math
 
n = int(input())
 
for data in sys.stdin:
    x1, y1, x2, y2, x3, y3 = map(float, data.split())
    a1 = x2 - x1
    b1 = y2 - y1
    a2 = x3 - x1
    b2 = y3 - y1
    px = (b2 * (a1 * a1 + b1 * b1) - b1 * (a2 * a2 + b2 * b2)) / (2 * (a1 * b2 - a2 * b1))
    py = (a1 * (a2 * a2 + b2 * b2) - a2 * (a1 * a1 + b1 * b1)) / (2 * (a1 * b2 - a2 * b1))
    r = math.sqrt(px * px + py * py)
    px += x1
    py += y1
    print("{0:.3f} {1:.3f} {2:.3f}".format(px, py, r))

Python: import cmath

class Point(object):
    def __init__(self, x, y):
        self.point = complex(x, y)
    def __str__(self):
        return "x = {0}, y = {1}".format(self.point.real, self.point.imag)

class Triangle(Point):
    def __init__(self, a, b, c):
        self.a = a
        self.b = b
        self.c = c
        # ３辺の長さ
        self.edgeA = abs(b.point-c.point)
        self.edgeB = abs(c.point-a.point)
        self.edgeC = abs(a.point-b.point)
        # ３角の大きさ
        self.angleA = Triangle.angle(self.edgeA, self.edgeB, self.edgeC)
        self.angleB = Triangle.angle(self.edgeB, self.edgeC, self.edgeA)
        self.angleC = Triangle.angle(self.edgeC, self.edgeA, self.edgeB)

    # 角度を求める
    def angle(A, B, C):
        return cmath.acos( (B*B+C*C-A*A)/(2*B*C) )


    # 外接円の半径
    def circumscribedCircleRadius(self):
        return abs((self.edgeA/cmath.sin(self.angleA))/2)

    # 外心
    def circumscribedCircleCenter(self):
        A = cmath.sin(2*self.angleA)
        B = cmath.sin(2*self.angleB)
        C = cmath.sin(2*self.angleC)
        X = (self.a.point.real*A + self.b.point.real*B + self.c.point.real*C) / (A+B+C)
        Y = (self.a.point.imag*A + self.b.point.imag*B + self.c.point.imag*C) / (A+B+C)
        return complex(X, Y)

line = list(map(float, input().split()))
p1 = Point(line[0], line[1])
p2 = Point(line[2], line[3])
p3 = Point(line[4], line[5])
T = Triangle(p1, p2, p3)
center = T.circumscribedCircleCenter()
print("{0:.4f} {1:.4f} {2:.4f}".format(center.real, center.imag, T.circumscribedCircleRadius()))

Python: # -*- coding: utf-8 -*-
from math import sqrt
# import numpy as np


n = int(input())

for i in range(n):
    tmp = input().split(' ')
    
    a, b, c = [(float(tmp[i]), float(tmp[i+1])) for i in range(0, len(tmp), 2)]
    
    #A = np.array(((a[0], a[1], 1),
    #              (b[0], b[1], 1),
    #              (c[0], c[1], 1)))
    A_tmp1 = 1/(a[0]*b[1] + a[1]*c[0] + b[0]*c[1] - b[1]*c[0] - a[1]*b[0] - a[0]*c[1])
    A_tmp2 = [[b[1]-c[1], -(a[1]-c[1]), a[1]-b[1]],
              [-(b[0]-c[0]),  (a[0]-c[0]), -(a[0]-b[0])],
              [b[0]*c[1] - b[1]*c[0], -(a[0]*c[1] - a[1]*c[0]), a[0]*b[1] - a[1]*b[0]]]
    A = [list(map(lambda x: A_tmp1*x, A_tmp2[i])) for i in range(3)]
    
    #B = np.array((((-(a[0]**2 + a[1]**2))),
    #              ((-(b[0]**2 + b[1]**2))),
    #              ((-(c[0]**2 + c[1]**2)))))
    B = [[-(a[0]**2 + a[1]**2)],
         [-(b[0]**2 + b[1]**2)],
         [-(c[0]**2 + c[1]**2)]]
    
    
    tmp = [sum([A[i][j]*B[j][0] for j in range(3)]) for i in range(3)]
    # tmp = np.dot(np.linalg.inv(A), B)
    print(tmp)
    
    x = -tmp[0]/2
    y = -tmp[1]/2
    r = sqrt((tmp[0]**2 + tmp[1]**2 - 4*tmp[2])/4)
    
    print('{:.3} {:.3} {:.3}'.format(x, y, r))

Python: from math import hypot

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

    d = lambda x, y: x*x + y*y
    t21 = [2*(x2-x1), 2*(y2-y1), d(x2,y2) - d(x1,y1)]
    t31 = [2*(x3-x1), 2*(y3-y1), d(x3,y3) - d(x1,y1)]

    det = lambda i, j: t21[i]*t31[j] - t21[j]*t31[i]
    a = det(2,1) / det(0,1)
    b = det(0,2) / det(0,1)
    r = hypot(x1-a, y1-b)

    print('{:.3f} {:.3f} {:.3f}'.format(a, b, r))