import re
pattern="^(?:\S.*\n)*.*((?<=^abc )\d+|x(?==\d+$))"
s = ("x=0\n"
"abc 20 \n"
"def 76 \n"
"ghi 11\n\n"
"x=1\n"
"def 45\n"
"ghi 32\n\n"
"x=2\n"
"jkl 56\n"
"mno 76\n"
"abc 134\n\n"
".\n"
".\n"
".\n\n"
"x=393\n"
"xyz 21\n"
"abc 9\n\n"
"x=394\n"
"ghi\n"
"def\n"
"xyz")
res=re.findall(pattern, s, re.M)
print(res)
aW1wb3J0IHJlCgpwYXR0ZXJuPSJeKD86XFMuKlxuKSouKigoPzw9XmFiYyApXGQrfHgoPz09XGQrJCkpIgpzID0gKCJ4PTBcbiIKCSJhYmMgMjAgICAgXG4iCgkiZGVmIDc2ICAgXG4iCgkiZ2hpIDExXG5cbiIKCSJ4PTFcbiIKCSJkZWYgNDVcbiIKCSJnaGkgMzJcblxuIgoJIng9MlxuIgoJImprbCA1NlxuIgoJIm1ubyA3NlxuIgoJImFiYyAxMzRcblxuIgoJIi5cbiIKCSIuXG4iCgkiLlxuXG4iCgkieD0zOTNcbiIKCSJ4eXogMjFcbiIKCSJhYmMgOVxuXG4iCgkieD0zOTRcbiIKCSJnaGlcbiIKCSJkZWZcbiIKCSJ4eXoiKQoKcmVzPXJlLmZpbmRhbGwocGF0dGVybiwgcywgcmUuTSkKcHJpbnQocmVzKQ==