def pairs(a,b):
tmp=[]
for aa in a:
for bb in b:
if aa==bb:
if aa not in tmp:
tmp+=a
# если нужны пары
print(str(tmp))
res=[]
for i in range(len(tmp)):
x=tmp[i]
res+=[(x,x)]
return res
x = ['a1', 'b1', 'c1', 'd1']
y = ['a1', 'b1', 'c1', 'd1', 'g1']
print(str(pairs(x,y)))
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
['a1', 'b1', 'c1', 'd1']
[('a1', 'a1'), ('b1', 'b1'), ('c1', 'c1'), ('d1', 'd1')]