prall-mm

def myLine(A1,B1,t, m=1):
  A = (A1[0]*m,A1[1]*m)
  B = (B1[0]*m,B1[1]*m)
  t.up(); t.goto(A)
  t.down(); t.goto(B)
def ilm(A1,t,m=1):
  A = (A1[0]*m,A1[1]*m)
  t.up(); t.goto(A[0]-(1*m),A[1]-(1*m));
  t.down(); t.color('blue'); t.write('A')
import turtle as tr
t1 = tr.Pen()
t1.speed(0)
t2 = t1.clone()
t1.width(3)
t1.color('red')
t2.color('gray')
A = (2,2)
B = (5,1)
C = (4,5)
mm = 20
def setka(A,B,t,m=1):
  for x in range(A[0],B[0]+1):
        myLine((x,A[1]),(x,B[1]),t2,mm)
  for y in range(A[0],B[0]+1):
        myLine((A[0],y),(B[0],y),t2,mm)
setka((0,0),(10,10),t2,mm)
myLine(A,B,t1,mm)
myLine(B,C,t1,mm)
myLine(C,A,t1,mm)
ilm(A,t1,mm)
ilm(B,t1,mm)
ilm(C,t1,mm)
tr.done()