File Operations

os.path module

• to verify if file and or dictionary exist

1. String-Based Operations: The os.path module primarily works with paths represented as strings.

2. Platform Independence: It provides functions for common path-related operations like joining paths, splitting paths, getting the basename, dirname, and more. These functions are designed to work across different operating systems (Windows, Unix, macOS).

3. Legacy: os.path has been around for a long time and is considered part of the legacy file path handling system in Python.

import os
os.path.exists('oops.txt')
# Output
# True
os.path.exists('./oops.txt')
# Output
# True
os.path.exists('.')
# Output
# True
os.path.exists('..')
# Output
# True

# Joining paths
path = os.path.join('folder', 'file.txt')

# Splitting paths
dirname, filename = os.path.split(path)

• single dot stands for current directory
• double dots stand for parent directory

pathlib module

1. Object-Oriented Approach: The pathlib module provides an object-oriented approach for working with paths. It represents paths as objects.

2. Rich API: It offers a rich API for path manipulation, making code more readable and expressive. Path objects have methods for various path operations.

3. Pure Path: Path objects in pathlib can represent both absolute and relative paths. They are platform-independent and provide consistent behavior across different operating systems.

4. Modern: pathlib is a more modern and preferred way of handling paths in Python, especially for new code.

from pathlib import Path

# Creating a path object
path = Path('folder') / 'file.txt'

# Getting parent directory
parent_dir = path.parent

Key Differences: Syntax: os.path uses string-based operations, while pathlib uses object-oriented syntax.

Object-Oriented vs. Functional: pathlib provides an object-oriented interface, making code more readable and allowing for method chaining. os.path uses functional programming style with standalone functions.

Ease of Use: pathlib is often considered more intuitive and easier to use for path manipulation, especially in modern Python code.

In summary, while both os.path and pathlib serve the purpose of working with filesystem paths,

• pathlib offers a more modern, object-oriented approach with a richer API, making it preferred for new development and cleaner code.
• os.path is still widely used, especially in legacy codebases.

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isfile() [to check type]

wether a name refers to a file, directory, or symbolic link

name='oops.txt'
os.path.isfile(name)
# Output
# True

isdir() [to determine directory]

name='oops.txt'
os.path.isdir('.')
# Output
# True

• isabs() determines wether its argument is an absolute pathname

os.path.isabs(name)
# Output
# False
os.path.isabs('/big/fake/name')
# Output
# True

copy() [for Copying]

• copying the file oops.txt to ohno.txt

import shutil
shutil.copy('oops.txt, ohno.txt')

shutil.move()link

• copies a file and then removes the original
• will raise an exception when your destination’s directory already has a file with the same name as the source.

rename() [to change file name]

import os
os.rename('nm.txt','name.txt')

Link with link() or symlink()

• hardlink: a file exists in one place but it can have multiple names, called links
  • link() call creates a hard link

Syntax

os.link('target.txt', 'link.txt')
os.isfile('link.txt')
# Output
# True

os.islink('link.txt')
# Output
# False

• symbolic link stores the new name as its own file, making it possible to get both the original and new names at once
  • symlink() call creates a symbolic link
• islink() checks wehter the dile is symbolic

Syntax

os.symlink(target, link)

import os
os.symlink('/path/to/target', '/path/to/link')

import os
is_symlink = os.path.islink('/path/to/link')

chmod() [to change permission]

• read, write, exucute permissions
• to make a file readable

os.chmod('oops.txt', 0o400)

# OR

import stat
os.chmod('oops.txt', stat.S_IRUSR)

chown() [to change ownership]

• numeric user ID (uid)
• group ID (gid)

uid = 5
gid = 22
os.chown('oops', uid,gid)

remove() [to delete a file]

import os
os.remove("oops.txt")
os.path.exists("oops.txt")
# OUTPUT
# False

Dictionary Operations

• container of all files and directories => filesystem is sometimes called volume

mkdir()

import os
os.mkdir('poems')
os.path.exists("poems")
# OUTPUT
# True

rmdir()

os.rmdir('poems')
os.path.exists("poems")
# OUTPUT
# False

listdir()

import os
os.mkdir('poems')

#get a list of its content
os.listdir('poems')
[]

# create subdirectory
os.mkdir('poems/goethe')
os.listdir('poems')
['goethe']

# create a file in this subdirectory
fout = open('poems/goethe/faust', 'wt')
fout.write(''' Two souls, alas, are housed within my breast,
And each will wrestle for the mastery there.''')
fout.close()

os.listdir('poems/goethe')
# OUTPUT
# ['faust']

chdir()

• going from one directory to another

  import os
  os.chdir('poems')
  os.listdir('.')
  # OUTPUT
  # ['faust']
  

globdir() [for list matching]

• matches file or directory names by using Unix shell rules:
• matches everything
• ? matches single character
• [abc] matches character a,b, or c

• [!abc] matches any character except a,b, or c

• getting all files or directories that beginn with f

import glob
glob.glob('f*')
# OUTPUT
# ['faust']

# any two letter files
import glob
glob.glob('??')
# OUTPUT
# ['']

Pathnames

• Mac uses forward slash

abspath()

os.path.abspath('oops.txt')
# OUTPUT
# [/usr/mike/oops.txt]

realpath() [to get a symlink Pathname]

• expands a relative name to an absolute one

os.path.abspath('oops.txt')
# Output
'/usr/mike/oops.txt'

os.path.join() [to build a pathname]

• combine multipart pathnames pairwise with proper patch seperation character

import os
my_file = os.path.join("eek", "urk")
my_file = os.path.join(my_file, "snort.txt")

> my_file
'eek/urk/snort.txt'

=> need to research this, no idea what this is about

pathlib

• it is an alternative to os.path module

import os

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From the exercises in the book

List the files in current dir

import os
os.listdir('.')
['bears', 'lions', 'tigers']

List the files in parent dir

import os
os.listdir('..')

assign the string to the variabl test1, ane write test1 to a file called test.txt

test1 = 'this is a test string'
outfile = open('test.txt', 'wt')
outfile.write(test1)
outfile.close

# alternitavely
with open('test.txt', 'wt') as outfile:
  outfile.write(test1)

• To avoid getting an error, you might want to check if the file exists before you try to delete it

import os
if os.path.exists("demofile.txt"):
  os.remove("demofile.txt")
else:
  print("The file does not exist")

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back

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