如何在Python中逐行比较两个不同的文件？

本教程介绍了使用Python可用模块、读取两个文件并逐行比较它们来执行这种典型工作的各种Python比较技术。

在Python中，可以通过多种方式比较两个文件。

逐行比较两个文本文件

通过使用open()函数从两个文本文件读取数据，我们可以比较它们包含的信息。open()函数将搜索本地目录并可能读取它。

示例

在此示例中，我们对比两个包含Python数据的文件。我们被告知这两个Python文件可能不相同，Python将为我们检查文件。可以使用readlines()方法从Python文件中提取行。

file1 = open('D:\Work TP/moving files.py', 'r')
file2 = open('D:\Work TP/mysql_access.py', 'r')
File3 = open('D:\Work TP/trial.py', 'w')

   for line1 in file1:
      for line2 in file2:
         if line1 == line2:
            File3.write("%s\n" %(line1))

File3.close()
file1.close()
file2.close()

在从文件中提取数据后，使用for循环逐行比较文件。如果行不匹配，用户将收到一条消息，告诉他们发生了不匹配的位置。为了让用户能够简单地找到不同的行，我们将包含数据本身。

输出

以下是上述代码的输出-

Line 1 doesn't match.
------------------------
File1: # importing the modules

File2: import mysql.connector

Line 2 doesn't match.
------------------------
File1: import os

File2: sampleDB=mysql.connector.connect(host='localhost',user='root',password='password',database='textx')

Line 3 doesn't match.
------------------------
File1: import shutil

File2: #print (sampleDB.connection_id)

Line 4 doesn't match.
------------------------
File1: # Providing the folder path

File2: cur=sampleDB.cursor()

Line 5 doesn't match.
------------------------
File1: origin = 'C:\Users\Lenovo\Downloads\Works\'

File2: s="CREATE TABLE novel(novelid integer(4),name varchar(20),price float(5,2))"

Line 6 doesn't match.
------------------------
File1: target = 'C:\Users\Lenovo\Downloads\Work TP\'

File2: cur.execute(s)

使用filecmp模块

通过filecmp模块可以在Python中处理文件。该模块专门设计用于比较两个或多个文件之间的数据。使用filecmp.cmp()方法，我们可以完成此操作。如果文件匹配，则该函数将返回True；否则，返回False。

示例

以下是使用filecmpule的示例−

import difflib

with open("D:\Work TP/moving files.py",'r') as file1:
   file1_info = file1.readlines()
with open("D:\Work TP/trial.py",'r') as file2:
   file2_info = file2.readlines()

diff = difflib.Differ().compare(file1_info, file2_info)

for line in diff:
   print(line)

输出

- # importing the modules
?    ^
+ import filecmp

  import os

- # Providing the folder path
-
- origin = 'C:\Users\Lenovo\Downloads\Works\'
- 
- target = 'C:\Users\Lenovo\Downloads\Work TP\'

- # Fetching the list of all the files
-
- files = os.listdir(origin)

- # Fetching all the files to directory
-
- for file_name in files:
-     shutil.copy2(origin+file_name, target+file_name)
- 
- print("Files are copied succesfully")
+ # notice the two backslashes
+ File1 = "D:\Work TP\moving files.py"
+ File2 = "D:\Work TP\trial.py"

+ def compare_files(File1,File2):
+    compare = filecmp.cmp(File1,File2)
+    
+    if compare == True:
+       print("The two files are the same.")
+    else:
+       print("The two files are different.")
+ 
+ compare_files(File1,File2)

使用difflib模块

为了比较文本并识别它们之间的变化，请使用difflib包。Python 3模块已经预装了此语言。它具有许多有用的比较文本样本的功能。

首先，我们将使用unified diff()函数识别两个数据文件之间的差异。然后，我们将比较这些文件。

示例1-使用unified-diff()

在下面的例子中，使用with语句读取文件数据。Python with语句允许我们安全地打开和读取文件。

import difflib

with open("D:\Work TP/moving files.py",'r') as file1:
   file1_info = file1.readlines()
with open("D:\Work TP/trial.py",'r') as file2:
   file2_info = file2.readlines()

diff = difflib.unified_diff(
   file1_info, file2_info, fromfile="file1.py",
   tofile="file2.py", lineterm='')

for lines in diff:
   print(lines)

输出

下面是上述代码的输出 –

--- file1.py
+++ file2.py
@@ -1,12 +0,0 @@

-# importing the modules

-import os

-import shutil

-# Providing the folder path

-origin = 'C:\Users\Lenovo\Downloads\Works\'

-target = 'C:\Users\Lenovo\Downloads\Work TP\'

-# Fetching the list of all the files

-files = os.listdir(origin)

-# Fetching all the files to directory

-for file_name in files:

- shutil.copy2(origin+file_name, target+file_name)

-print("Files are copied succesfully")

示例2-使用differ()

在difflib库中，有一个名为Differ的类可用于比较文件差异。该类用于比较文本行组并生成增量或差异。

以下是使用differ()方法逐行比较两个不同文件的示例 –

from difflib import Differ

with open('D:\Work TP/moving files.py') as file1, open('D:\Work TP/trial.py') as file2:
   vary = Differ()

for lines in vary.compare(file1.readlines(), file2.readlines()):
   print(lines)

输出

以下是上述代码的输出 –

- # importing the modules

- import os

- import shutil

- # Providing the folder path

- origin = 'C:\Users\Lenovo\Downloads\Works\'

- target = 'C:\Users\Lenovo\Downloads\Work TP\'

- # Fetching the list of all the files

- files = os.listdir(origin)

- # Fetching all the files to directory

- for file_name in files:

- shutil.copy2(origin+file_name, target+file_name)

- print("Files are copied succesfully")