Python:比较两组并将结果写入第三组

Question

所以这就是我所拥有的,我认为我正在寻找的是非常直截了当的.我希望能够将c2中不在c1中的项目添加到c3中.设置c1和c2正确填充.任何帮助表示赞赏.谢谢.

import csv
import sys
c1 = set()
c2 = set()
c3 = set()

with open(new, 'r') as newfile:
    newreader = csv.reader(newfile, delimiter=('|'))
    for row in newreader:
        c1.add(row[0])

with open(new, 'r') as oldfile:
    oldreader = csv.reader(oldfile, delimiter=('|'))
    for row in oldreader:
        c2.add(row[0])

for item in c2:
    if item not in c1:
        c3.add(item)

print(c1)
print(c2)
print(c3)

Answer 1

尝试:

c3 = c2 - c1

这很容易.

甚至:

c3 |= c2 - c1

如果c3已经有一些内容.

请参阅:https: //docs.python.org/2/library/sets.html