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: import math

class P(object):
    def __init__(self, x, y):
        self.x = x
        self.y = y

    def width(self, p):
        return math.sqrt((self.x - p.x)**2 + (self.y - p.y)**2)

    def __repr__(self):
        return '{0:.3f} {1:.3f}'.format(self.x, self.y)

def calc_cos(a,b,c):
    return (b**2 + c**2 - a**2) / (2*b*c)

def calc_sin(c):
    return math.sqrt(1 - c**2)

def calc_2sin(s,c):
    return 2 * s * c

def run():
    n = int(input())
    for _ in range(n):
        x1, y1, x2, y2, x3, y3 = list(map(float, input().split()))
        p1, p2, p3 = P(x1, y1), P(x2, y2), P(x3, y3)
        a, b, c = p1.width(p2), p2.width(p3), p3.width(p1)
        cosA, cosB, cosC = calc_cos(a,b,c), calc_cos(b,c,a), calc_cos(c,a,b)
        sinA, sinB, sinC = calc_sin(cosA), calc_sin(cosB), calc_sin(cosC)
        sin2A, sin2B, sin2C = calc_2sin(sinA, cosA), calc_2sin(sinB, cosB), calc_2sin(sinC, cosC)

        r = a / sinA / 2

        x = (p1.x * sin2B + p2.x * sin2C + p3.x * sin2A) / (sin2A + sin2B + sin2C)
        y = (p1.y * sin2B + p2.y * sin2C + p3.y * sin2A) / (sin2A + sin2B + sin2C)

        print('{0:.3f} {1:.3f} {2:.3f}'.format(x,y,r))

if __name__ == '__main__':
    run()

Python: import math

class Circle:
    def __init__(self,x,y,r):
        self.x = x
        self.y = y
        self.r = r

def getCircle(x1, y1, x2, y2, x3, y3):
    d = 2 * (x1 * (y2 - y3) + x2 * (y3 - y1) + x3 * (y1 - y2))
    px = ((x1**2 + y1**2) * (y2 - y3) + (x2**2 + y2**2) * (y3 - y1) + (x3**2 + y3**2) * (y1 - y2) ) / d
    py = ((x1**2 + y1**2) * (x3 - x2) + (x2**2 + y2**2) * (x1 - x3) + (x3**2 + y3**2) * (x2 - x1) ) / d
    a = math.sqrt((x1 - x2)**2 + (y1 - y2)**2)
    b = math.sqrt((x1 - x3)**2 + (y1 - y3)**2)
    c = math.sqrt((x2 - x3)**2 + (y2 - y3)**2)
    s = (a + b + c) / 2
    A = math.sqrt(s * (s - a) * (s - b) * (s - c))
    r = a * b * c / (4 * A)
    return Circle(px,py,r)

          
n = int(input())
for k in range(n):
    x1, y1, x2, y2, x3, y3 = [float(x) for x in input().split()]
    circle = getCircle(x1, y1, x2, y2, x3, y3)
    print("%.3f %.3f %.3f" % (circle.x, circle.y, circle.r))

Python: # -*- coding:utf-8 -*-

import sys
import math

def solve(x1,y1,x2,y2,x3,y3):
    z1 = -1 * (x1**2 + y1**2)
    z2 = -1 * (x2**2 + y2**2)
    z3 = -1 * (x3**2 + y3**2)

    a11,a12,a13 = x1,y1,1
    a21,a22,a23 = x2,y2,1
    a31,a32,a33 = x3,y3,1
    det = a11*a22*a33 + a21*a32*a13 + a31*a12*a23 - a11*a32*a23 - a31*a22*a13 - a21*a12*a33

    l = ((a22*a33 - a23*a32)*z1 + (a13*a32 - a12*a33)*z2 + (a12*a23 - a13*a22)*z3)/det
    m = ((a23*a31 - a21*a33)*z1 + (a11*a33 - a13*a31)*z2 + (a13*a21 - a11*a23)*z3)/det
    n = ((a21*a32 - a22*a31)*z1 + (a12*a31 - a11*a32)*z2 + (a11*a22 - a12*a21)*z3)/det

    x,y,r = round(-l/2,3),round(-m/2,3),round(math.sqrt((l**2)/4+(m**2)/4-n),3)
    sol = [x, y, r]
    return sol


n,count = int(input()),0
array = []
for i in sys.stdin:
    array.append(i)
    count += 1
    if count == n:
        break

    
for i in range(len(array)):
    x = array[i]
    p = x.split()
    res = solve(float(p[0]),float(p[1]),float(p[2]),float(p[3]),float(p[4]),float(p[5]))
    print('{:.3f} {:.3f} {:.3f}'.format(res[0], res[1], res[2]))

Python: from __future__ import (division, absolute_import, print_function,
                        unicode_literals)
from sys import stdin
from math import sqrt
N = int(stdin.readline())
for i in xrange(N):
    x1, y1, x2, y2, x3, y3 = (float(n) for n in stdin.readline().split())
    det = x1*y2 + x2*y3 + x3*y1 - x1*y3 - x2*y1 - x3*y2
    a = x1**2 + y1**2
    b = x2**2 + y2**2
    c = x3**2 + y3**2
    L = (a*y2 + b*y3 + c*y1 - a*y3 - b*y1 - c*y2) / det
    M = (x1*b + x2*c + x3*a - x1*c - x2*a - x3*b) / det
    N = (x1*y2*c + x2*y3*a + x3*y1*b - x1*y3*b - x2*y1*c - x3*y2*a) / det
    xp = L / 2.0
    yp = M / 2.0
    r = sqrt(abs(N + xp**2.0 + yp**2.0))
    print('{:.3f} {:.3f} {:.3f}'.format(xp, yp, r))

Python: from math import sqrt
n=input()
for i in range(n):
	x1,y1,x2,y2,x3,y3=map(float,raw_input().split())
	A1=2*(x2-x1)
	B1=2*(y2-y1)
	C1=x2**2+y2**2-x1**2-y1**2
	x=((C1*B2)-(C2*B1))/((A1*B2)-(A2*B1))
	y=((A1*C2)-(A2*C1))/((A1*B2)-(A2*B1))