输入一个正整数，若是有一对质数的和等于该正整数，则返回全部的质数对

 

def fun(a=int):    list1=[]    list2=[]    for i in range(2,int(a/2)+1):        for j in range(2,int(i/2)):            if i%j==0:                list1.append(j)        if len(list1)!=0:            list1=[]        else:            for k in range(2,int((a-i)/2)):                if (a-i)%k==0:                    list1.append(k)            if len(list1)!=0:                list1=[]            else:                list2.append((i,a-i))    print(list2)