Go: package main

import (
	"fmt"
	"math"
)

func main() {
	var num int
	fmt.Scan(&num)
	for i := 0; i < num; i++ {
		var x1, y1, x2, y2, x3, y3 float64
		fmt.Scanf("%f%f%f%f%f%f", &x1, &y1, &x2, &y2, &x3, &y3)

		a := 2 * (x2 - x1)
		b := 2 * (y2 - y1)
		c := 2 * (x3 - x1)
		d := 2 * (y3 - y1)
		e := x2*x2 - x1*x1 + y2*y2 - y1*y1
		f := x3*x3 - x1*x1 + y3*y3 - y1*y1

		// 直線1: ax + by - e = 0
		// 直線2: cx + dy - f = 0
		px := (d*e - b*f) / (a*d - b*c)
		py := (c*e - a*f) / (b*c - a*d)
		r := math.Sqrt((px-x1)*(px-x1) + (py-y1)*(py-y1))
		fmt.Printf("%.3f %.3f %.3f\n", px, py, r)
	}
}

Python: def main():
    import math
    for i in range(int(input())):
        x1,y1,x2,y2,x3,y3=map(float,input().split())

        a=y1-y2
        b=y1-y3

        if a==0:
            x=(x1+x2)/2
            c=(x3-x1)/(y1-y3)
            d=(-x1-x3)/2+(y1+y3)/2
            y=c*x+d

        elif b==0:
            x=(x1+x3)/2
            c=(x2-x1)/(y1-y2)
            d=(-x1-x2)/2+(y1+y2)/2
            y=c*x+d

        else:
            a=(x2-x1)/(y1-y2)
            b=(-x1-x2)/2+(y1+y2)/2
            c=(x3-x1)/(y1-y3)
            d=(-x1-x3)/2+(y1+y3)/2

            x=(d-b)/(a-c)
            y=a*x+b

        r=math.sqrt((x-x1)**2+(y-y1)**2)

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

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


# n = int(input())
# tmp = input().split(' ')
tmp = '0.0 0.0 2.0 0.0 2.0 2.0'.split(' ')
# tmp = '0.0 3.0 -1.0 0.0 -3.0 4.0'.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)))

B = np.array((((-(a[0]**2 + a[1]**2))),
              ((-(b[0]**2 + b[1]**2))),
              ((-(c[0]**2 + c[1]**2)))))

tmp = np.dot(np.linalg.inv(A), B)

#tmp = [-6, 10, 18]

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().split())
	x4=((y1-y3)*(y1**2-y2**2+x1**2-x2**2)-(y1-y2)*(y1**2-y3**2+x1**2-x3**2))/(2*(y1-y3)*(x1-x2)-2*(y1-y2)*(x1-x3))
	y4=((x1-x3)*(x1**2-x2**2+y1**2-x1**2)-(x1-x2)*(x1**2-x3**2+y1**2-y3**2))/(2*(x1-x3)*(y1-y2)-2*(x1-x2)*(y1-y3))
	r=hypot(x1-x4,y1-y4)
	print("{:.3f} {:.3f} {:.3f}".format(x4,y4,r))

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)
    
    x = -tmp[0]/2
    y = -tmp[1]/2
    r = sqrt((tmp[0]**2 + tmp[1]**2 - 4*tmp[2])/4)
    
    print('{:.3f} {:.3f} {:.3f}'.format(x, y, r))

Python: for _ in[0]*int(input()):
 a,b,c,d,e,f=map(float,input().split())
 x=((a*a+b*b)*(d-f)+(c*c+d*d)*(f-b)+(e*e+f*f)*(b-d))/2/(a*(d-f)+c*(f-b)+e*(b-d))
 y=((a*a+b*b)*(c-e)+(c*c+d*d)*(e-a)+(e*e+f*f)*(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: import math

def run():
    n = int(input())
    for _ in range(n):
        x1, y1, x2, y2, x3, y3 = list(map(float, input().split()))
        u1 = (x1-x3)*(x2-x1)*(x3-x2)
        u2 = (x2-x1)*(y3-y2)*(y3+y2)
        u3 = (x3-x2)*(y2-y1)*(y2+y1)
        v = x1*x2 + x2*y3 + x3*y1 - x1*y3 - x2*y1 + x3*y2
        Py = (-u1 + u2 - u3) / v / 2
        Px = (x2**2 - x1**2 + y2**2 - y1**2 - (y2 - y1)*Py) / (x2-x1) / 2
        r = math.sqrt((Px-x1)**2 + (Py-y1)**2)
        print('{0:.3f} {1:.3f} {2:.3f}'.format(round(Px,3), round(Py,3), round(r,3)))

if __name__ == '__main__':
    run()

Python: #!/usr/bin/env python
from math import *
def g(x):
	y = (int((1000 * abs(x)) * 2 + 1) // 2) / 1000
	return y / abs(y) * y
def func(x):
	x1, y1, x2, y2, x3, y3 = x

	vx1 = x2 - x1
	vy1 = y2 - y1
	vx2 = x3 - x1
	vy2 = y3 - y1
	k = (vx2 ** 2 + vy2 ** 2 - vx1 * vx2 - vy1 * vy2) / (vy1 * vx2 - vx1 * vy2) / 2
	x = vx1 / 2 + k * vy1 + x1
	y = vy1 / 2 - k * vx1 + y1
	r = sqrt((x1 - x) ** 2 + (y1 - y) ** 2)
	print("{0:.3f} {1:.3f} {2:.3f}".format(g(x), g(y), g(r)))
n = int(input())
for _ in range(n):
	func(list(map(float, input().split())))

Python: import math
n=int(input())
for i in range(n):
  x1,y1,x2,y2,x3,y3=map(float,input().split())
  a=(x3-x1)*(x1**2+y1**2-x2**2-y2**2)-(x2-x1)*(x1**2+y1**2-x3**2-y3**2)
  b=2*(x3-x1)*(y1-y2)-2*(x2-x1)*(y1-y3)
  py=a/b
  if x2-x1!=0:
    px=(2*(y1-y2)*py-x1**2-y1**2+x2**2+y2**2)/(2*(x2-x1))
  else:
    px=(2*(y1-y3)*py-x1**2-y1**2+x3**2+y3**2)/(2*(x3-x1))
  r=math.sqrt((px-x1)**2+(py-y1)**2)
  print(f"{px:.3f}",f"{py:.3f}",f"{r:.3f}")

Python: # Aizu Problem 0010: Circumscribed Circle of a Triangle
#
import sys, math, os

# read input:
PYDEV = os.environ.get('PYDEV')
if PYDEV=="True":
    sys.stdin = open("sample-input.txt", "rt")


def circumscribed_circle(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 = .5 * abs((x2 - x1) * (y3 - y1) - (x3 - x1) * (y1 - y1))
    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)
    r = a * b * c / (4 * A)
    return px, py, r

          
N = int(input())
for k in range(N):
    x1, y1, x2, y2, x3, y3 = [float(_) for _ in input().split()]
    px, py, r = circumscribed_circle(x1, y1, x2, y2, x3, y3)
    print("%.3f %.3f %.3f" % (px, py, r))

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(f'{x:.3f} {y:.3f} {((x-a)**2+(y-b)**2)**.5:.3f}')

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

import sys
import os
import math


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

    c = 2 * ((x2 - x1) * (y3 - y1) - (y2 - y1) * (x3 - x1))
    x = ((y3 - y1) * (x2 ** 2 - x1 ** 2 + y2 ** 2 - y1 ** 2) + (y1 - y2) * (x3 ** 2 - x1 ** 2 + y3 ** 2 - y1 ** 2)) / c
    y = ((x1 - x3) * (x2 ** 2 - x1 ** 2 + y2 ** 2 - y1 ** 2) + (x2 - x1) * (x3 ** 2 - x1 ** 2 + y3 ** 2 - y1 ** 2)) / c
    r = math.sqrt((x1 - x) ** 2 + (y1 - y) ** 2)

    print("{:.3f} {:.3f} {:.3f}".format(x, y, r))