【文件处理】文件（夹）的一些常用处理总结

文件（夹）的一些常用处理总结。

文件的一般读入写入总结

• with open 比 open 多一个 自动 close 操作。

基本操作

函数名	操作
.read()	读取文件所有内容
.readlines()	将每行文件内容存入列表读取
.write()	写入文件

参数的问题

• reference

	r	r+	w	w+	a	a+
read	O	O		O		O
write		O	O	O	O	O
create			O	O	O	O
truncate			O	O
position at start	O	O	O	O
position at end					O	O

• truncate means delete the content of the file.

• Some differences
  • The r throws an error if the file does not exist or opens an existing file without truncating it for reading; the file pointer position at the beginning of the file.
  • The r+ throws an error if the file does not exist or opens an existing file without truncating it for reading and writing; the file pointer position at the beginning of the file.
  • The w creates a new file or truncates an existing file, then opens it for writing; the file pointer position at the beginning of the file.
  • The w+ creates a new file or truncates an existing file, then opens it for reading and writing; the file pointer position at the beginning of the file.
  • The a creates a new file or opens an existing file for writing; the file pointer position at the end of the file.
  • The a+ creates a new file or opens an existing file for reading and writing, and the file pointer position at the end of the file.

文件（夹）不存在，则创建

• 文件夹不存在，则创建的问题。
• 文件（如test.txt）不存在，创建（写入）的问题。
• 文件夹及文件都不存在，创建（写入）的问题。
  • 先创建文件夹，再创建（写入）文件。

若文件夹不存在，则创建

import os

def if_folder_exists(folder_path):
    if not os.path.exists(folder_path):
        os.makedirs(folder_path)

若文件不存在，则创建（写入）

• 参考上文-参数的问题-w或者w+

分离路径和文件名 以及 分离文件名和后缀

import os
 
file_path = "D:/pzlu/test.py"
(filepath, tempfilename) = os.path.split(file_path) # 分离路径和文件名
(filename, extension) = os.path.splitext(tempfilename) # 分离文件名和后缀

遍历文件夹下所有文件及目录

显示目录下所有文件

import os 

g = os.walk(r"e:\test")  

for path,dir_list,file_list in g:
    # 文件夹路径, 文件夹名字, 文件名
    for file_name in file_list:  
        print(os.path.join(path, file_name) )

显示所有子目录

import os 

g = os.walk("e:\test")  

for path,dir_list,file_list in g:  
    for dir_name in dir_list:
        print(os.path.join(path, dir_name) )