如何比较2个文件只获取不​​在第二个文件中的行？

Question

我有两个这样的文件：

file 1 :                     file 2 :
col1    col2                 col1     col2
john    kerry                john     kerry
adam    lord                 bob      abram  
joe     hitch               

我想基于lastnames和firstnames比较这两个文件，只得到一个不包含文件2中人员的文件，也就是说：

desired output file :

col1     col2
adam     lord
joe      hitch

我尝试了这个，但我没有得到正确的输出

import csv

reader1=csv.reader(open('file1.csv', 'r'), delimiter='\t')
reader2=csv.reader(open('file2.csv', 'r'), delimiter='\t')
writer=csv.writer(open('desired_file.csv', 'w'), delimiter=',')

row1 = reader1.next()
row2 = reader2.next()

if (row1[0] == row2[0]) and (row1[1] == row2[1]):
    print 'equal'
else:
    writer.writerow(row1)
    writer.writerow(row2)

Answer 1

我会使用一组差异：

with open('file1') as f1, open('file2') as f2:
    data1 = set(f1)
    lines_not_in_f2 = data1.difference(f2)

如果文件的格式可能略有不同，您可能需要将文件对象包装在生成元组的生成器中：

def people(my_file):
    for line in myfile:
        yield tuple(x.lower() for x in line.split())

with open('file1') as f1, open('file2') as f2:
    data1 = set(people(f1))
    people_not_in_f2 = data1.difference(people(f2))

这样做的好处是您不需要将整个f2文件读入内存。它的缺点是输出名称是无序的（因为它们存储在一个集合中）。

Answer 2

如果文件格式相同，我认为您不需要csv模块。 这个解决方案怎么样：

exclude_names = frozenset(open('file2')) # make set for performance
with open('output', 'w') as f:
    for name in open('file1'):
        if name not in exclude_names:
             f.write(name)

csv读者/作者的解决方案：

import csv

exclude_names = frozenset(csv.reader(open('file2.csv', 'r'), delimiter='\t'))    
with open('desired_file.csv', 'w') as f:
    writer = csv.writer(f, delimiter=',')
    for row in csv.reader(open('file1', 'r'), delimiter='\t'):
         if row not in exclude_names:
              writer.writerow(row)

Answer 3

results=[i for i, j in zip(reader1, reader2) if i != j]

如果订单不重要，请使用set(reader1) - set(reader2)。

myfile = open(..., 'wb')
wr = csv.writer(myfile, quoting=csv.QUOTE_ALL)
wr.writerow(results)