2020-06-21 Python

File Systems

Python File Systems

Working with the file system

Files

• Filename
• Filetype - file extensions (.png, .jpg) is extra info for humans, software actually uses the filetype

Directories

Folders

Tracing up directories takes you to the root directory. On Windows that is a drive letter like C:\ On Posix it would be just a /

Official word for slashes / is seperators

On windows: backslashes lean to the left \ On linux: forward slashes lean to the right /

OS

>>> import os
>>> os.getcwd
<built-in function getcwd>
>>> os.getcwd()
'/Users/surfer190/projects/fixes'
>>> os.chdir('..')
>>> os.getcwd()
'/Users/surfer190/projects'

Use os.getcwd() to get current working directory Use os.chdir('..') to go back a directory

Paths

• Absolute path - full path from the root
• Relative path - path from another directory

.. - move up one directory . - means current directory

To check if a path is absolute use os.paths.isabs(<path>)

>>> os.path.isabs('/Users')
True
>>> os.path.isabs('workspaces/')
False

Path does not actually have to exist

Link to os documentation

When joining paths python will know what seperator to use with:

    os.path.join(os.getcwd(), 'backups')

Can also add multiple paths

    os.path.join(os.getcwd(), '..', 'backups')

Pathlib

Library for working with paths

Here are sone docs for pathlib, pure paths and concrete paths

    >>> import pathlib
    >>> path = pathlib.PurePath(os.getcwd())
    >>> path
    PurePosixPath('/Users/surfer190/projects')

You can join paths with the / operator

    >>> path2 = path / 'examples' / 'paths.txt'
    >>> path2
    PurePosixPath('/Users/surfer190/projects/examples/paths.txt')

Check the parts

    >>> path2.parts
    ('/', 'Users', 'stephen', 'projects', 'examples', 'paths.txt')

The root or parent

    >>> path2.root
    '/'
    >>> path2.parents[2]
    PurePosixPath('/Users/surfe190')

Get the filename and suffix

    >>> path2.name
    'paths.txt'
    >>> path2.suffix
    '.txt'

Back to OS

Check the file and folders in working directory

    >>> os.listdir()

You can provide a path

    >>> os.listdir('my/path`)

Another way is using scandir which returns an iterable

    >>> list(os.scandir())

Returns a DirEntry

    >>> file
    <DirEntry 'README.md'>
    >>> file.name
    'README.md'
    >>> file.is_file()
    True

Get stats on a file

    >>> file.stat()
    os.stat_result(st_mode=33188, st_ino=6361471, st_dev=16777220, st_nlink=1, st_uid=501, st_gid=20, st_size=3115, st_atime=1482839524, st_mtime=1452884872, st_ctime=1452884872)

st_size returns the file size in bytes

If you are not using scandir in an iterable or with a context with then you need to close it.

    >>> scanner = os.scandir()
    >>> scanner.close()

Script to show filesize per folder

    import os

    def treewalker(start):
        total_size = 0
        total_files = 0

        for root, dirs, files in os.walk(start):
            subtotal = sum(
            os.path.getsize(os.path.join(root, name)) for name in files
            )
            total_size += subtotal
            file_count = len(files)
            total_files += file_count
            print(root, "consumes", end=" ")
            print(subtotal, end=" ")
            print("bytes in", file_count, "non-directory files")
        print(start, "contains", total_files, "files with a combined size of", total_size, "bytes")

    treewalker('../fixes')

Utilities

Check if a file or directory exists

>>> os.path.exists('bootstrap')
False

Creating a file

open('test_file.txt', 'w').close()
open('test_file.txt', 'a').close()

w - is truncate a - is append

On mac you have to be running python as root to use:

    os.mknod('/mysir/myfile.txt')

By default permissions it creates is 0660

Make a directory:

    os.mkdir('templates')

Can create multiple at once with:

    os.makedirs('layouts/mobile/apple')

Best thing is create even if a directory already exists:

    os.makedirs('layouts/mobile/apple', exist_ok=True)

Rename a single file:

    os.rename('test_file.txt', 'test.txt')

Rename directories:

    os.renames('assets', 'static/raw')

Replace a directory

    >>> os.replace('templates', 'boiling')

Get file extension without pathlib

Source

    >>> import os
    >>> filename, file_extension = os.path.splitext('/path/to/somefile.ext')
    >>> filename
    '/path/to/somefile'
    >>> file_extension
    '.ext'

File Deletions

    >>> import os

Remove a file

    >>> os.remove('bootstrap/bootstrap.js')

Remove an empty directory, an error given if not empty

    >>> os.rmdir('bootstrap/img')

Deleting a directory that is not empty

    for thing in os.scandir('bootstrap/js'):
        if thing.is_file():
            os.remove(thing.path)

    os.rmdir('bootstrap/js')

Make dirs

    os.makedirs('bootstrap/js/packages/stuff')
    os.removedirs('bootstrap/js/packages/stuff')

Will remove everything except directory not empty

Send2Trash

There is a package called send2trash

    from send2trash import send2trash

    send2trash('tree.py')

Working with temporary files, dirctories and friends

    import tempfile

Using the TemporaryDirectory:

    with tempfile.TemporaryDirectory() as tmpdirname:
        print("Printed temporary directory named: {}".format(tmpdirname))
        with open(os.path.join(tmpdirname, 'temp_file.txt'), 'w') as f:
            f.write('hello\n')
        input()

Using TemporaryFile:

    fp = tempfile.TemporaryFile()
    fp.write(b'hello\n')
    fp.close()

To be able to find the file later on:

    fp = tempfile.NamedTemporaryFile()
    fp.name