参见英文答案 > Difference Between Two Lists with Duplicates in Python4个
我有3个列表,我想找到第1 /第2和第2 /第3之间的差异
并打印出来.

这是我的代码：

n1 = [1,1,2,3] 
n2 = [1,2] # Here the 3 is not found ("3" is not present in n1 at all)
n3 = [1,2]   # here 1 is not found (there are fewer "1"s in n3 than in n2)
for x in n1: 
   if x not in n2:
      print x  
for m in n2: 
   if m not in n3: 
      print m 

但我得到的输出只有3.

如何使它输出1和3？我也尝试使用套装,但它只打印了3次.

最佳答案
由于您似乎关心在两个列表中找到项目的次数,您需要从您要比较的列表中删除匹配的项目：

comp = n2[:]  # make a copy
for x in n1:
    if x not in comp:
        print x
    else:
        comp.remove(x)
# output: 3

或使用collections.Counter

from collections import Counter
print Counter(n1) - Counter(n2)
# output: Counter({3: 1})

它告诉你n1中哪些项不在n2中,或者在n1中比在n2中更常见.

所以,例如：

>>> Counter([1,3]) - Counter([1,2])
Counter({2: 2,3: 1})