fraction addition precoded in Latex

def st(num):
    if num<0:
        return '('+str(num)+')'
    else: return str(num)
from random import*
array=[1,2,3,5,7,11,13,17]

o=[]
ats=[]
while(len(o)<28):
    aa=randint(0,16)
    bb=randint(0,16)
    cc=randint(0,16)
    dd=randint(0,16)
    a=[-1,-2,-3,-5,-7,-11,-13,-17, 0, 1,2,3,5,7,11,13,17][aa]
    b=[-1,-2,-3,-5,-7,-11,-13,-17, 0, 1,2,3,5,7,11,13,17][bb]
    c=[-1,-2,-3,-5,-7,-11,-13,-17, 0, 1,2,3,5,7,11,13,17][cc]
    d=[-1,-2,-3,-5,-7,-11,-13,-17, 0, 1,2,3,5,7,11,13,17][dd]
    #=[1,2,3,5,7,11,13,17][randint(0,7)]
    i=a*d+b*c
    j=b*d
    o.append('\\task $ \\frac{'+str(a)+'}{'+str(b)+'}'+'+ \\frac{'+str(c)+'}{'+str(d)+'}$')
    if i==0: ats.append('\\task $0$')
    elif abs(j)==1: ats.append('\\task $'+str(i*j)+'$')
    elif j==0: ats.append('\\task E')
    elif i==0: ats.append('\\task $0$')
    elif i==j: ats.append('\\task $'+ ['-',''][(i*j/abs(i*j)+1)/2]+'1'+'$')
    else: ats.append('\\task $'+ ['-',''][(i*j/abs(i*j)+1)/2]+'\\frac{'+str(abs(i))+'}{'+str(abs(j))+'}'+'$')
print '\\begin{tasks}(4)'
for n in o: print n
print '\\end{tasks}'
print '\\begin{tasks}(6)'
for n in ats: print n
print '\\end{tasks}'