Buggy python submission (verdict: Runtime Error):
import math
for i in range(input()):
    x1,y1,x2,y2,x3,y3=map(float,raw_input().split(" "))
    if y2==y1 or y3==y1:
        if y2==y1:
            a2=-(x2-x1)/(y3-y1)
            b2=((y3+y1)-a2*(x1+x3))/2
            a,b,c,d,e,f,=1,0,(x1+x2)/2,1,-a2,b2
        else:
            a1=-(x2-x1)/(y2-y1)
            b1=((y2+y1)-a2*(x1+x2))/2
            a,b,c,d,e,f,=1,-a1,b1,1,0,(x1+x3)/2
    else:
        a1=-(x2-x1)/(y2-y1)
        a2=-(x3-x1)/(y3-y1)
        b1=((y2+y1)-a1*(x1+x2))/2
        b2=((y3+y1)-a2*(x1+x3))/2
        a,b,c,d,e,f,=1,-a1,b1,1,-a2,b2
    py=(a*f-c*d)/(a*e-b*d)
    px=(c*e-f*b)/(a*e-b*d)
    r=math.sqrt((px-x1)**2 + (py-y1)**2)
    print "{0:.3f} {1:.3f} {2:.3f}".format(px,py,r)

Fixed submission:
import math
for i in range(input()):
    x1,y1,x2,y2,x3,y3=map(float,raw_input().split(" "))
    if y2==y1 or y3==y1:
        if y2==y1:
            a2=-(x3-x1)/(y3-y1)
            b2=((y3+y1)-a2*(x1+x3))/2.0
            a,b,c,d,e,f=1.0,0.0,(x1+x2)/2.0,-a2,1.0,b2
        else:
            a1=-(x2-x1)/(y2-y1)
            b1=((y2+y1)-a1*(x1+x2))/2.0
            a,b,c,d,e,f=-a1,1.0,b1,1.0,0.0,(x1+x3)/2.0
    else:
        a1=-(x2-x1)/(y2-y1)
        a2=-(x3-x1)/(y3-y1)
        b1=((y2+y1)-a1*(x1+x2))/2.0
        b2=((y3+y1)-a2*(x1+x3))/2.0
        a,b,c,d,e,f=-a1,1.0,b1,-a2,1.0,b2
    py=(a*f-c*d)/(a*e-b*d)
    px=(c*e-f*b)/(a*e-b*d)
    r=math.sqrt((px-x1)**2 + (py-y1)**2)
    print "{0:.3f} {1:.3f} {2:.3f}".format(px,py,r)

Buggy python submission (verdict: Runtime Error):
import math
for i in range(input()):
    x1,y1,x2,y2,x3,y3=map(float,raw_input().split(" "))
    if y2==y1 or y3==y1:
        if y2==y1:
            a2=-(x3-x1)/(y3-y1)
            b2=((y3+y1)-a2*(x1+x3))/2
            a,b,c,d,e,f,=0,1,(x1+x2)/2,-a2,1,b2
        else:
            a1=-(x2-x1)/(y2-y1)
            b1=((y2+y1)-a2*(x1+x2))/2
            a,b,c,d,e,f,=-a1,1,b1,0,1,(x1+x3)/2
    else:
        a1=-(x2-x1)/(y2-y1)
        a2=-(x3-x1)/(y3-y1)
        b1=((y2+y1)-a1*(x1+x2))/2
        b2=((y3+y1)-a2*(x1+x3))/2
        a,b,c,d,e,f,=-a1,1,b1,-a2,1,b2
    py=(a*f-c*d)/(a*e-b*d)
    px=(c*e-f*b)/(a*e-b*d)
    r=math.sqrt((px-x1)**2 + (py-y1)**2)
    print "{0:.3f} {1:.3f} {2:.3f}".format(px,py,r)

Fixed submission:
import math
for i in range(input()):
    x1,y1,x2,y2,x3,y3=map(float,raw_input().split(" "))
    if y2==y1 or y3==y1:
        if y2==y1:
            a2=-(x3-x1)/(y3-y1)
            b2=((y3+y1)-a2*(x1+x3))/2.0
            a,b,c,d,e,f=1.0,0.0,(x1+x2)/2.0,-a2,1.0,b2
        else:
            a1=-(x2-x1)/(y2-y1)
            b1=((y2+y1)-a1*(x1+x2))/2.0
            a,b,c,d,e,f=-a1,1.0,b1,1.0,0.0,(x1+x3)/2.0
    else:
        a1=-(x2-x1)/(y2-y1)
        a2=-(x3-x1)/(y3-y1)
        b1=((y2+y1)-a1*(x1+x2))/2.0
        b2=((y3+y1)-a2*(x1+x3))/2.0
        a,b,c,d,e,f=-a1,1.0,b1,-a2,1.0,b2
    py=(a*f-c*d)/(a*e-b*d)
    px=(c*e-f*b)/(a*e-b*d)
    r=math.sqrt((px-x1)**2 + (py-y1)**2)
    print "{0:.3f} {1:.3f} {2:.3f}".format(px,py,r)

Buggy python submission (verdict: Runtime Error):
import math
for i in range(input()):
    x1,y1,x2,y2,x3,y3=map(float,raw_input().split(" "))
    if y2==y1 or y3==y1:
        if y2==y1:
            a2=-(x3-x1)/(y3-y1)
            b2=((y3+y1)-a2*(x1+x3))/2
            a,b,c,d,e,f=0,1,(x1+x2)/2,-a2,1,b2
        else:
            a1=-(x2-x1)/(y2-y1)
            b1=((y2+y1)-a2*(x1+x2))/2
            a,b,c,d,e,f=-a1,1,b1,0,1,(x1+x3)/2
    else:
        a1=-(x2-x1)/(y2-y1)
        a2=-(x3-x1)/(y3-y1)
        b1=((y2+y1)-a1*(x1+x2))/2
        b2=((y3+y1)-a2*(x1+x3))/2
        a,b,c,d,e,f=-a1,1,b1,-a2,1,b2
    py=(a*f-c*d)/(a*e-b*d)
    px=(c*e-f*b)/(a*e-b*d)
    r=math.sqrt((px-x1)**2 + (py-y1)**2)
    print "{0:.3f} {1:.3f} {2:.3f}".format(px,py,r)

Fixed submission:
import math
for i in range(input()):
    x1,y1,x2,y2,x3,y3=map(float,raw_input().split(" "))
    if y2==y1 or y3==y1:
        if y2==y1:
            a2=-(x3-x1)/(y3-y1)
            b2=((y3+y1)-a2*(x1+x3))/2.0
            a,b,c,d,e,f=1.0,0.0,(x1+x2)/2.0,-a2,1.0,b2
        else:
            a1=-(x2-x1)/(y2-y1)
            b1=((y2+y1)-a1*(x1+x2))/2.0
            a,b,c,d,e,f=-a1,1.0,b1,1.0,0.0,(x1+x3)/2.0
    else:
        a1=-(x2-x1)/(y2-y1)
        a2=-(x3-x1)/(y3-y1)
        b1=((y2+y1)-a1*(x1+x2))/2.0
        b2=((y3+y1)-a2*(x1+x3))/2.0
        a,b,c,d,e,f=-a1,1.0,b1,-a2,1.0,b2
    py=(a*f-c*d)/(a*e-b*d)
    px=(c*e-f*b)/(a*e-b*d)
    r=math.sqrt((px-x1)**2 + (py-y1)**2)
    print "{0:.3f} {1:.3f} {2:.3f}".format(px,py,r)