Python file and directory operation code summary

Foreword

In python, a file object is built-in, and file operations can be realized through some built-in methods, such as the open() method to create a file object, and the write() method to write content to the file.

1. Basic file operation

1. Create and open files

To manipulate a file, you must first create or open the specified file and create a file object, which can be achieved through the built-in function open().

file =open(file_name[,mode[,buffering]])'''
file_name :File name to be created or opened
mode: Used to specify how the file is opened
'''

Parameter value table of mode parameter

note

When opening a file with the open() function, GBK encoding is used by default. If you want to use other encoding methods, you need to add the encoding parameter

file = open(‘./text.txt’,’a+’,encoding=’utf-8′)

Need to use the original file encoding method to open, otherwise an error will be reported

2. Close file

After opening the file, it needs to be closed in time to avoid unnecessary damage to the file. You can use the built-in function close().

file = open(‘./text.txt’,’a+’)
file.close()

Note

The close() function first refreshes the information that has not been written in the buffer, writes it to the file, and then closes the file to protect the file.

3. Write to file

grammar

file = write(string)

demo

# open a file
file =open('./text.txt','a+')
# Write file
file =write('Live up to code, live up to Qing')
# Close file
file.close()

Note:

When writing the file again, inject the mode in which the file was opened, otherwise the original data will be overwritten.

4. Read file

The prerequisite for reading the file is that when the file is opened, the specified open mode is r (read-only) or r+ (read-write). Otherwise, an exception will be thrown.

(1) Read the specified characters

file.read([size])

size: Used to specify the number of characters to be read, if omitted, all content will be read at once.

(2) Read one line

file.readline()

This method is used to read a line of text

(3) Read all rows

file.readlins()

2. Directory operations

Python has a built-in os module and submodule os.path for manipulating directories or files.

Directory-related functions provided by the os module

The os.path module provides functions related to directories

demo —— Get the current working directory

import os
print(os.getcwd())

demo —— Determine whether the directory exists

import os
print(os.path.exists(“c:\demo”))

Note

Because exists() is provided by the submodule of os, you need to add a prefix, os.path

demo —— Create a first-level directory

import os
path ="c://demo"
# If the directory to be created already exists, an exception will be thrown, first determine whether the directory to be created exists
if not os.path.exists(path):
	os.mkdir(path)else:print('The directory already exists')

Note

The directory created by mkdir(path) is a first-level directory. If the last-level parent directory in the passed path does not exist, an exception will be thrown.

demo —— Create a multi-level directory

import os
os.makedirs(“C:\demo1\demo2\…”)

demo —— delete directory

import os
path ="C:\demo1\demo2"
# Determine the directory to be deleted, if it does not exist, it will throw a problem
if os.path.exists(path):
	os.rmdir("C:\demo1\demo2") #Deleted the demo2 file
	print("Directory deleted successfully!")else:print("The directory does not exist")

Note:

The rmdir() function can only delete empty directories. If they are not empty, they cannot be deleted. You can delete non-empty directories with the following code.

import shutil
shutil.rmtree("C:\demo\text")

demo-traverse directories

The return value of os.walk() is a tuple generator object containing three elements (dirpath, dirnams, filenames).

dirpath: is a string representing the path currently traversed

dirnames: is a list representing the subdirectories contained in the current path

filenames: is also a list of files in the current directory

os.walk(top,[topdown][,onerror][,followlinks])'''
top:Used to specify the directory to be traversed
topdown:Optional parameter, used to specify the order to be traversed, if True (default), it means traversal from top to bottom, if False,Means from childhood to top.
'''

import os
path ="C:\demo"
# root is the current root path, dirs contains the subdirectories under the path, files contains the two to five years under the subdirectories
for root,dirs,fles in os.walk(path,topdown=True):for name in dirs:print(os.path.join(root,name))for name in files:print(os.path.join(root.name))

demo-find whether a file exists in the current directory

import os
path ="C:\demo"
filename ="love.txt"for root,dirs,files in os.walk(path):for name in files:if filename== name:print(os.path.join(root,name))

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