python - 返回两个文件之间不同的行（Python）

Question

我有两个文件，每个文件都有数万行，output1.txt 和 output2.txt。我想遍历这两个文件并返回两者之间不同的行（和内容）。它们大多相同，这就是我找不到差异的原因（filecmp.cmp 返回 false）。

Answer 1

7.4. difflib — 计算增量的助手

2.1 版中的新功能。

该模块提供用于比较序列的类和函数。例如，它可以用于比较文件，并且可以生成各种格式的差异信息，包括 HTML 和上下文以及统一差异。要比较目录和文件，另请参阅 filecmp 模块。

Answer 2

只要您不关心订单，您就可以使用：

with open('file1') as f:
    t1 = f.read().splitlines()
    t1s = set(t1)

with open('file2') as f:
    t2 = f.read().splitlines()
    t2s = set(t2)

#in file1 but not file2
print "Only in file1"
for diff in t1s-t2s:
    print t1.index(diff), diff

#in file2 but not file1
print "Only in file2"
for diff in t2s-t1s:
    print t2.index(diff), diff

编辑：如果您确实关心订单并且它们几乎相同，那么为什么不使用命令diff呢？

Answer 3

你可以这样做：

import difflib, sys

tl=100000    # large number of lines

# create two test files (Unix directories...)

with open('/tmp/f1.txt','w') as f:
    for x in range(tl):
        f.write('line {}\n'.format(x))

with open('/tmp/f2.txt','w') as f:
    for x in range(tl+10):   # add 10 lines
        if x in (500,505,1000,tl-2):
            continue         # skip these lines
        f.write('line {}\n'.format(x))        

with open('/tmp/f1.txt','r') as f1, open('/tmp/f2.txt','r') as f2:
    diff = difflib.ndiff(f1.readlines(),f2.readlines())    
    for line in diff:
        if line.startswith('-'):
            sys.stdout.write(line)
        elif line.startswith('+'):
            sys.stdout.write('\t\t'+line)   

打印（400 毫秒）：

- line 500
- line 505
- line 1000
- line 99998
        + line 100000
        + line 100001
        + line 100002
        + line 100003
        + line 100004
        + line 100005
        + line 100006
        + line 100007
        + line 100008
        + line 100009

如果您想要行号，请使用枚举：

with open('/tmp/f1.txt','r') as f1, open('/tmp/f2.txt','r') as f2:
    diff = difflib.ndiff(f1.readlines(),f2.readlines())    
    for i,line in enumerate(diff):
        if line.startswith(' '):
            continue
        sys.stdout.write('My count: {}, text: {}'.format(i,line))