Buggy python submission (verdict: Runtime Error):
H,W=map(int,input().split())
s="#"*W+"".join("#"+input()for _ in range(H))
f=-~W*-~H
d=[[0]*f for _ in range(f)]
for i in range(W,f-1):
 d[i][i-1]=s[i]==s[i-1]=="."
 d[i][i-W-1]=s[i]==s[i-W-1]=="."
from scipy.sparse.csgraph import csgraph_from_dense as C,floyd_warshall as F
import numpy as p
Q=F(C(d),directed=False)
print(int(max(Q[Q!=p.inf])))

Fixed submission:
import math
N, = map(int, input().split())
xs = []
ys = []
for _ in range(N):
    x, y = map(int, input().split())
    xs.append(x)
    ys.append(y)

def bb(a,b,c,d,e,f):
    if not (c-a)*(f-b)-(e-a)*(d-b):
        return None, None
    aa = a * a
    bb = b * b
    cc = c * c
    dd = d * d
    ee = e * e
    ff = f * f
    py = ((e - a) * (aa + bb - cc - dd) - (c - a) * (aa + bb - ee- ff)) / (2 * (e - a)*(b - d) - 2 * (c - a) * (b - f))
    px = (2 * (b - f) * py - aa - bb + ee + ff) / (2 * (e - a)) \
        if (c == a) else (2 * (b - d) * py - aa - bb + cc + dd) / (2 * (c - a))
    return px, py


pxs = []
pys = []
for i in range(N):
    for j in range(i+1, N):
        for k in range(j+1, N):
#            print(i,j,k)
            px, py = bb(xs[i],ys[i],xs[j],ys[j],xs[k],ys[k])
            if not px:
                continue
            pxs.append(px)
            pys.append(py)
for i in range(N):
    for j in range(i+1, N):
        pxs.append((xs[i]+xs[j])/2)
        pys.append((ys[i]+ys[j])/2)

rr = 10**10
for px, py in zip(pxs,pys):
    r = 0
    for x, y in zip(xs, ys):
        r = max(r, (x-px)**2+(y-py)**2)
    rr = min(rr, r)
print(rr**0.5)

Buggy python submission (verdict: Runtime Error):
import math
N, = map(int, input().split())
xs = []
ys = []
for _ in range(N):
    x, y = map(int, input().split())
    xs.append(x)
    ys.append(y)

def bb(a,b,c,d,e,f):
    aa = a * a
    bb = b * b
    cc = c * c
    dd = d * d
    ee = e * e
    ff = f * f
    py = ((e - a) * (aa + bb - cc - dd) - (c - a) * (aa + bb - ee- ff)) / (2 * (e - a)*(b - d) - 2 * (c - a) * (b - f))
    px = (2 * (b - f) * py - aa - bb + ee + ff) / (2 * (e - a)) \
        if (c == a) else (2 * (b - d) * py - aa - bb + cc + dd) / (2 * (c - a))
    return px, py


pxs = []
pys = []
for i in range(N):
    for j in range(i+1, N):
        for k in range(j+1, N):
            px, py = bb(xs[i],ys[i],xs[j],ys[j],xs[k],ys[k])
            pxs.append(px)
            pys.append(py)
for i in range(N):
    for j in range(i+1, N):
        pxs.append((xs[i]+xs[j])/2)
        pys.append((ys[i]+ys[j])/2)

rr = 10**10
for px, py in zip(pxs,pys):
    r = 0
    for x, y in zip(xs, ys):
        r = max(r, (x-px)**2+(y-py)**2)
    rr = min(rr, r)
print(rr**0.5)


Fixed submission:
import math
N, = map(int, input().split())
xs = []
ys = []
for _ in range(N):
    x, y = map(int, input().split())
    xs.append(x)
    ys.append(y)

def bb(a,b,c,d,e,f):
    if not (c-a)*(f-b)-(e-a)*(d-b):
        return None, None
    aa = a * a
    bb = b * b
    cc = c * c
    dd = d * d
    ee = e * e
    ff = f * f
    py = ((e - a) * (aa + bb - cc - dd) - (c - a) * (aa + bb - ee- ff)) / (2 * (e - a)*(b - d) - 2 * (c - a) * (b - f))
    px = (2 * (b - f) * py - aa - bb + ee + ff) / (2 * (e - a)) \
        if (c == a) else (2 * (b - d) * py - aa - bb + cc + dd) / (2 * (c - a))
    return px, py


pxs = []
pys = []
for i in range(N):
    for j in range(i+1, N):
        for k in range(j+1, N):
#            print(i,j,k)
            px, py = bb(xs[i],ys[i],xs[j],ys[j],xs[k],ys[k])
            if not px:
                continue
            pxs.append(px)
            pys.append(py)
for i in range(N):
    for j in range(i+1, N):
        pxs.append((xs[i]+xs[j])/2)
        pys.append((ys[i]+ys[j])/2)

rr = 10**10
for px, py in zip(pxs,pys):
    r = 0
    for x, y in zip(xs, ys):
        r = max(r, (x-px)**2+(y-py)**2)
    rr = min(rr, r)
print(rr**0.5)