7.1. File Path¶

7.1.1. Rationale¶

Python works with both relative and absolute path
Path separator \ (backslash) is used on Windows
Path separator / (slash) is used on *nix operating systems: Linux, macOS, BSD and other POSIX compliant OSes (excluding Windows)
In newer Windows versions both \ and / works the same

Absolute path on Windows:

>>> FILE = r'C:\Users\Watney\myfile.txt'

Absolute path on *nix (Linux, macOS, BSD, etc.):

>>> FILE = '/tmp/myfile.txt'

Relative paths works the same on Windows and *nix (Linux, macOS, BSD, etc.):

>>> FILE = 'myfile.txt'
>>> FILE = 'tmp/myfile.txt'
>>> FILE = '../myfile.txt'

7.1.2. Good Engineering Practices¶

Never hardcode paths, use constant as a file name or file path
Convention (singular form): FILE, FILENAME, FILEPATH, PATH
Convention (plural form): FILES, FILENAMES, FILEPATHS, PATHS

Note, that PATH is usually used for other purposes (sys.path or os.getenv('PATH'))

>>> FILE = 'myfile.txt'

>>> FILES = [
...     'myfile.txt',
...     'myfile.csv']

7.1.3. Raw Strings¶

Always use raw-strings (r"...") for paths

Escapes does not matters

>>> print(r'C:\Users\Admin\file.txt')
C:\Users\Admin\file.txt

>>> print('C:\\Users\\Admin\\file.txt')
C:\Users\Admin\file.txt

>>> print('C:\Users\Admin\file.txt')
Traceback (most recent call last):
SyntaxError: (unicode error) 'unicodeescape' codec can't decode bytes in position 2-3: truncated \UXXXXXXXX escape

Problem: \Users
after \U... python expects Unicode codepoint in hex i.e. 'U0001F680' which is 🚀 emoticon
s is invalid hexadecimal character

Only valid characters are 0123456789abcdefABCDEF

>>> import string
>>>
>>>
>>> print(string.hexdigits)
0123456789abcdefABCDEF

7.1.4. Absolute Path¶

Absolute path on Windows starts with drive letter
Absolute path on *nix starts with root / dir

Absolute path include all entries in the directories hierarchy

>>> FILE = r'C:\Users\Watney\myfile.txt'

>>> FILE = r'/tmp/myfile.txt'

7.1.5. Relative Path¶

Path is relative to currently running script
. - Current directory
.. - Parent directory

>>> FILE = r'myfile.txt'
>>> FILE = r'./myfile.txt'

>>> FILE = r'tmp/myfile.txt'
>>> FILE = r'./tmp/myfile.txt'

>>> FILE = r'../myfile.txt'
>>> FILE = r'../tmp/myfile.txt'

>>> FILE = r'../../myfile.txt'
>>> FILE = r'../../tmp/myfile.txt'

7.1.6. Escaping Characters in Path¶

"\ " (backslash space) - escapes space

Note that in Python escapes in paths are not required

>>> FILE = '/tmp/my file.txt'

>>> FILE = r'/tmp/my file.txt'

>>> FILE = r'C:\Users\Admin\myfile.txt'
>>>
>>>
>>> repr(FILE)
"'C:\\\\Users\\\\Admin\\\\myfile.txt'"
>>>
>>> str(FILE)
'C:\\Users\\Admin\\myfile.txt'
>>>
>>> print(repr(FILE))
'C:\\Users\\Admin\\myfile.txt'
>>>
>>> print(FILE)
C:\Users\Admin\myfile.txt

7.1.7. Exception Handling¶

>>> try:
...     file = open('/tmp/myfile.txt')
... except FileNotFoundError:
...     print('Sorry, file not found')
... except PermissionError:
...     print('Sorry, not permitted')
Sorry, file not found

7.1.8. Create Directories¶

>>> from pathlib import Path
>>>
>>> Path('/tmp/a').mkdir()

>>> from pathlib import Path
>>>
>>> Path('/tmp/a').mkdir()
Traceback (most recent call last):
FileExistsError: [Errno 17] File exists: '/tmp/a'

>>> from pathlib import Path
>>>
>>> Path('/tmp/a').mkdir(exist_ok=True)

>>> from pathlib import Path
>>>
>>> Path('/tmp/a/b/c').mkdir(parents=True, exist_ok=True)

7.1.9. Touch File¶

>>> from pathlib import Path
>>>
>>> Path('/tmp/myfile.txt').touch()

7.1.10. Exists and is Directory or File¶

>>> from pathlib import Path
>>>
>>> Path('/tmp/myfile.txt').exists()
True

>>> from pathlib import Path
>>>
>>> Path('/tmp/myfile.txt').is_dir()
False

>>> from pathlib import Path
>>>
>>> Path('/tmp/myfile.txt').is_file()
True

7.1.11. Delete directory¶

Works only with empty directories:

>>> from pathlib import Path
>>>
>>> Path('/tmp/a').rmdir()
Traceback (most recent call last):
OSError: [Errno 66] Directory not empty: '/tmp/a'

Remove directories with files:

>>> from shutil import rmtree
>>>
>>> rmtree('/tmp/a', ignore_errors=True)

7.1.12. Current Working Directory¶

Returns an absolute path to current working directory

>>> from pathlib import Path
>>>
>>> # doctest: +SKIP
... Path.cwd()
PosixPath('/home/python/')

7.1.13. Convert Relative Path to Absolute¶

>>> from pathlib import Path
>>>
>>> # doctest: +SKIP
... Path(Path.cwd(), 'myfile.txt')
PosixPath('/home/python/myfile.txt')

7.1.14. Script Path¶

Returns an absolute path to currently running script

>>> print(__file__)  # doctest: +SKIP
/home/python/myscript.py

7.1.15. Assignments¶

Code 7.1. Solution¶

"""
* Assignment: File Path Exception
* Filename: file_path_exception.py
* Complexity: easy
* Lines of code: 6 lines
* Time: 3 min

English:
    1. Using `input()` ask user for a file path
    3. Handle exception for not existing file
    4. Handle exception for not having sufficient permissions

Polish:
    1. Używając `input()` zapytaj użytkownika o ścieżkę do pliku
    3. Obsłuż wyjątek dla nieistniejącego pliku
    4. Obsłuż wyjątek dla braku wystarczających uprawnień

Tests:
    TODO: Doctests
    TODO: Input Stub
"""


# Given
filename = input('Type filename: ')

Code 7.2. Solution¶

"""
* Assignment: File Path Abspath
* Filename: file_path_abspath.py
* Complexity: easy
* Lines of code: 3 lines
* Time: 5 min

English:
    1. Define `path` with converted `filename` to absolute path
    2. Print if path exists and leads to file or directory
    3. Compare result with "Tests" section (see below)

Polish:
    1. Zdefiniuj `path` z przekonwertowym `filename` do ścieżki bezwzględnej
    2. Wypisz czy ścieżka istnieje i czy prowadzi do pliku czy katalogu
    3. Porównaj wyniki z sekcją "Tests" (patrz poniżej)

Tests:
    TODO: Input Stub
    >>> isinstance(result, Path)
    True
    >>> current_directory = Path.cwd()
    >>> str(current_directory) in str(result)
    True
"""


# Given
from pathlib import Path


filename = 'myfile.txt'
path = ...
result = ...