Little knowledge , Great challenge ！ This article is participating in “ A programmer must have a little knowledge ” Creative activities .

1. Get all files in the current directory

have access to os.listdir(path) function , It can return to path The specified folder contains file or Folder A list of names .

How to use it is as follows ：

import os

#  Open file 
path = "D://data/"
dirs = os.listdir( path )

#  Output all files and folders 
for file in dirs:
   print (file)
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2. Traverse folders, including subfolders

have access to os.walk(path) function , It can traverse all the files in the directory by swimming through the directory tree .

It returns a triple (root, dirs, files) The generator ,

• root It refers to the address of the folder being traversed
• dirs It's a list , The contents are the names of all the directories in the folder （ Exclude subdirectories ）
• files It's a list , The content is all the files in the folder （ Exclude subdirectories ）

How to use it is as follows ：

import os

path = "D://data/"
for root, dirs, files in os.walk(path):
    for name in files:
        print(os.path.join(root, name))
    for name in dirs:
        print(os.path.join(root, name))
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3. Other commonly used OS operation

In addition, there are some commonly used os operation , Such as os.path.exists(path) and os.makedirs(path).

• os.path.exists(path) Used to determine path Does the path exist , return true or false .
• os.makedirs(path) Used to create path route .

For example, when downloading files , Hope you can Breakpoint continuation , That is, when downloading a file , First judge whether the file exists in the local path .

if not os.path.exists(path):
    #todo: download file
    downloadFile(path)
else:
    pass
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Sometimes when saving files , If the path does not exist, it may fail to save and report an error , So you can first judge whether the path exists , If it does not exist , First create .

if not os.path.exists(path):
    # create path
    os.makedirs(path)
    
# todo: save file
saveFiles()
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