str_a = "liuke,test.ok"
str_b = "liuke.test.yes"
tmp = []
# 遍歷：從最長的開始
for i in range(len(str_a), 0, -1):
for j in range(len(str_a) + 1 - i):
sub = str_a[j:j + i]
# 得到子串，判斷其是否在str_b中
if sub in str_b:
tmp.append(sub)
# 找到公共子串，跳出外層循環
if tmp:
break
print(tmp)
End