在Python中逐行比较两个文件

在Python中，有许多方法可用于这种比较。在本文中，我们将了解如何 逐行比较两个不同的文件。 Python支持许多模块来这样做，在这里我们将讨论使用其各种模块的方法。

本文使用两个示例文件进行实现。

使用中的文件：

• 文件.txt

• 文件1.txt

方法一：使用unified_diff()

Python有一个模块，专门用于比较文件之间的差异。要使用difflib库获取差异，我们必须调用统一的_diff()函数进行此比较。

Syntax:

unified_diff(file1, file2, fromfile, tofile, lineterm)

Parameter:

• file1: List of String such as file_1_text
• file2: List of String such as file_2_text
• fromfile: first file name with extension
• tofile: second file name with extension
• lineterm: argument to “” so that the output will be automcally uniformly newline free

方法

• 导入模块
• 打开文件
• 使用 Unified_diff() 与适当的属性进行比较

例子：

Python3

# Importing difflib
import difflib
  
with open('file1.txt') as file_1:
    file_1_text = file_1.readlines()
  
with open('file2.txt') as file_2:
    file_2_text = file_2.readlines()
  
# Find and print the diff:
for line in difflib.unified_diff(
        file_1_text, file_2_text, fromfile='file1.txt', 
        tofile='file2.txt', lineterm=''):
    print(line)

输出：

— file1.txt

+++ file2.txt

@@ -1,5 +1,5 @@

 Learning

 Python

 is

-too

-simple.

+so

+easy.

方法 2：使用不同

有一个类可用于比较difflib库中名为Differ的文件之间的差异。此类用于比较文本行的序列，并生成人类可读的差异或增量。

Code	Meaning
‘-‘	line unique to sequence 1
‘+’	line unique to sequence 2
‘ ‘	line common to both sequences
‘?’	line not present in either input sequence

方法

• 导入模块
• 打开文件
• 读取内容行 bt 行
• 使用不同的类对象调用比较函数

例子：

蟒蛇3

from difflib import Differ
  
with open('file1.txt') as file_1, open('file2.txt') as file_2:
    differ = Differ()
  
    for line in differ.compare(file_1.readlines(), file_2.readlines()):
        print(line)

输出：

Learning

Python

is

– too

– simple.

+ so

+ easy.

方法三：使用while循环和Intersection方法

方法

• 以读取模式打开两个文件
• 存储字符串列表
• 在常见字符串的intersection() 方法的帮助下开始比较两个文件
• 使用 while 循环比较两个文件的差异
• 关闭两个文件

例子：

蟒蛇3

# Open File in Read Mode
file_1 = open('file1.txt', 'r')
file_2 = open('file2.txt', 'r')
  
print("Comparing files ", " @ " + 'file1.txt', " # " + 'file2.txt', sep='\n')
  
file_1_line = file_1.readline()
file_2_line = file_2.readline()
  
# Use as a COunter
line_no = 1
  
print()
  
with open('file1.txt') as file1:
    with open('file2.txt') as file2:
        same = set(file1).intersection(file2)
  
print("Common Lines in Both Files")
  
for line in same:
    print(line, end='')
  
print('\n')
print("Difference Lines in Both Files")
while file_1_line != '' or file_2_line != '':
  
    # Removing whitespaces
    file_1_line = file_1_line.rstrip()
    file_2_line = file_2_line.rstrip()
  
    # Compare the lines from both file
    if file_1_line != file_2_line:
        
        # otherwise output the line on file1 and use @ sign
        if file_1_line == '':
            print("@", "Line-%d" % line_no, file_1_line)
        else:
            print("@-", "Line-%d" % line_no, file_1_line)
              
        # otherwise output the line on file2 and use # sign
        if file_2_line == '':
            print("#", "Line-%d" % line_no, file_2_line)
        else:
            print("#+", "Line-%d" % line_no, file_2_line)
  
        # Print a empty line
        print()
  
    # Read the next line from the file
    file_1_line = file_1.readline()
    file_2_line = file_2.readline()
  
    line_no += 1
  
file_1.close()
file_2.close()

输出：

Comparing files 

 @ file1.txt

 # file2.txt

Common Lines in Both Files

Learning

Python

is

Difference Lines in Both Files

@- Line-4 too

#+ Line-4 so

@- Line-5 simple.

#+ Line-5 easy.