Working with directories¶

Importing the os module¶

Here, we will for the first time use a function that is not readily available in Python - it needs to be imported:

import os

os is the name of a module that is automatically installed with Python. It is simply not kept in memory all the time. This is why we need to import it.

Listing files in a directory:¶

The function

y = os.listdir("my_folder")

gives you a list of all files in the directory my_folder and stores it in the variable y.

Changing directories¶

With the os module, you can change the current directory:

import os
os.chdir('../python')

Check whether a file exists¶

print(os.path.exists('my_file.txt'))

Check file modification time¶

import time

t = os.path.getmtime('/home/krother/.bashrc')
gmt = time.gmtime(t)
time.strftime("%Y-%m-%d, %H:%M:%S", gmt)

Overview¶

The table lists some frequently used functions in os:

function	description
`os.listdir(path)`	returns list of file names in `path`
`os.remove(path)`	removes a file
`os.getcwd()`	returns current working directory
`os.path.exists(path)`	checks whether the given file or directory exists
`os.path.isdir(path)`	checks whether the given path is a directory
`os.path.isfile(path)`	checks whether the given path is a file
`os.path.getsize(path)`	returns file size
`os.path.getmtime(path)`	returns modification time
`os.path.split(path)`	cuts off the last dir/file name
`os.path.join(d1, d2, d3, ..)`	connects names by path separator
`os.environ[key]`	dictionary of environment variables
`os.system(cmd)`	executes shell command