Reading, writing and organizing files

Navigating through system

Path library

The Path module from the pathlib library allows to manipulate file paths and navigate through the system. These are some functions in the Path module:

>>> from pathlib import Path
>>> Path('folder', 'subfolder', 'file.txt')  # returns path (adapted to os)
PosixPath('folder/subfolder/file.txt')
>>> Path.home()                              # returns home directory
PosixPath('/home/user')
>>> Path.cwd()                               # get current working directory
PosixPath('/home/user/current/working/directory')

# Getting ancestor folder of a path
>>> Path.cwd().parents[0]
PosixPath('/home/user/current/working')
>>> Path.cwd().parents[1]
PosixPath('/home/user/current/')
>>> Path.cwd().parents[5]
PosixPath('/home')

# get the attributes of a path
>>> p = Path('/home/user/current/file.txt')
>>> p.anchor
'/'
>>> p.parent
PosixPath('/home/user/current/file.txt')
>>> p.name
'file.txt'
>>> p.stem
'file'
>>> p.suffix
'.txt'
>>> p.drive  # what's before the anchor ('C:' in Windows)
''
>>> p.exists() # check if file/dir exists
True
>>> p.is_dir() # check if it is a directory
False
>>> p.is_file() # check if it is a file
True

os library

Another library used for navigation and manipulation of files and directories is os. This library is older than pathlib, so it can do most of the things that pathlib does. Here are some useful functions not covered by the latter:

>>> import os
>>> os.makedirs('/home/user/new/folder/paths')  # create one or multiple folders
>>> os.path.abspath('.')  # returns the absolute path
>>> os.path.isabs('.')  # boolean if path is absolute
False
>>> os.sep  # gets the separator for the OS
'/'  # '\\' for Windows
>>> os.path.getsize('./path') # returns path's size
23453
>>> os.listdir('./path')
['list', 'with', 'files.xlsx']

>>> list(Path.cwd().glob('*.txt'))  # get list of txt files in cwd
[PosixPath('./file.txt')], PosixPath('./file2.txt')

Function	Description
`Path.home()`	returns home directory
`Path.cwd()`	returns current working directory
`p.parents[n]`	p being a path object, parents[n] return n up parent folders path
`p.anchor`	returns path anchor
`p.parent`	returns Path object with p path
`p.name`	returns file name with extension
`p.stem`	returns file name without extension
`p.suffix`	returns file extension
`p.drive`	returns what’s before the anchor “C:” for Windows
`list(p.glob('*.txt'))`	returns all the documents that match the pattern (regex-like) in that directory
`p.exists()`	boolean to check if p exists
`p.is_file()`	boolean to check if p is a file
`p.is_dir()`	boolean to check if p is a directory
`os.makedirs(path)`	creates one or more folders
`os.pah.abspath('.')`	returns absolute path of the argument
`os.path.isabs('.')`	boolean, returns if path is absolute
`os.sep`	returns the operating system separator
`os.path.getsize(path)`	returns path’s size in bytes
`os.listdir(path)`	returns list with files and folders in path

Reading/Writing process

The more common way of writing or reading a file is using the open(file, mode) function and file objects. The steps to follow are:

Call the open() function to return a File object.
Call the read() or write() method on the File object.
Close the file by calling the close() method on the File object.

file = open('some_file.txt', 'r') # read, r is default
file.read() # returns string with text
file.readlines() # returns list of strings, where each element is a line

file = open('some_file.txt', 'w') # write
file.write('write this text to a file.\n')

file = open('some_file.txt', 'a') # append
file.write('this text will be appended to the file')

file.close() # closes the file

Organizing files

Shell utilities (shutil)

The built-in module shutilhas functions to copy, move, rename and delete files.

Copy, move and rename

import shutil, os
from pathlib import Path

# Copy
>>> shutil.copy('./test.txt', './src/') # copy to src folder
'./src/test.txt'
>>> shutil.copy('./test.txt', './src/test2.txt') # copy with different name
'./src/test2.txt'

# Move and rename
>>> shutil.move('./test.txt', './src/') # move to src folder
'./src/test.txt'
>>> shutil.move('./test.txt', './src/test2.txt') # move and rename
'./src/test2.txt'

Safely removing files with send2trash

To send a file/folder to trash instead of permanently removing it, the third party library send2trash can be used.

Syntax: send2trash.send2trash('filename.txt')

Walking a directory tree

To iterate over all the folder and files inside a folder the os.walk(path) function can be used. It returns three values on each iteration of the loop:

a string of the curent folder’s name,
a list of strings of folders in the current folder,
a list of strings of files in the current folder

import os

for folderName, subfolders, filenames in os.walk('pathto/foldertowalk/'):
    print('The current folder is ' + folderName)

    for subfolder in subfolders:
        print('SUBFOLDER OF ' + folderName + ': ' + subfolder)

    for filename in filenames:
        print('FILE INSIDE ' + folderName + ': '+ filename)

    print('')

Compressing files

Reading ZIP files

To read a zip file and explore its contents:

>>> import zipfile, os
>>> from pathlib import Path

>>> zip = zipfile.ZipFile('./src.zip')  # create object for compressed file
>>> zip.namelist()  # get contents
['src/', 'src/SUMMARY.md', 'src/homepage.md', 'src/regex.md', 'src/read_write.md']
>>> file = zip.getinfo('src/regex.md')  # select a file to get info
>>> file.file_size  # file size
9078
>>> file.compress_size  # compressed file size
3173
>>> zip.close()  # close zip file

Extracting from zip files

>>> zip = zipfile.ZipFile('./src.zip')
>>> zip.extractall()  # extract all files in zip to cwd
>>> zip.extract('src/regex.md', './some/folder')  # extract only given file to given path
>>> zip.close()

Creating a zip file

Works similar to the read() method. The zip file has to be opened using zip = zipfile.ZipFile(zipfile) but specifying a second argument: w or a for writting and appending respectively.

>>> newZip = zipfile.ZipFile('new.zip', 'w')  # write mode
>>> newZip.write('spam.txt', compress_type=zipfile.ZIP_DEFLATED)  # compress spam.txt
>>> newZip.close()

Organizing functions summary

Function	Description
`shutil.copy(source, destination)`	copy file at source to destination folder
`shutil.copytree(source, destination)`	copy folder along with subfolders/files to destination
`shutil.move(source, destination)`	move file at source to destination folder
`os.unlink(path)`	delete file at path
`os.rmdir(path)`	delete folder at path, it has to be empty
`os.rmtree(path)`	delete folder at path along with all its files and subfolders
`send2trash.send2trash(file)`	send a file to trash instead of permanent deletion
`os.walk(path)`	iterate over all files under path
`zip = zipfile.ZipFile(zipfile)`	read zip file
`zip.namelist()`	get contents from zipfile
`zip.extractall(path)`	extract files from zip to path, defaults to cwd
`zip.extract(file, path)`	extract only selected file from zip to given path; if path isn’t given it defaults to cwd
`newzip = zipfile.ZipFile(newzip, w)`	open zip file in write mode
`newzip.write(file, compress_type)`	writes a file into a zip file, the compress_type defines the compression algorithm