File and path in python with pathlib api

Publié le 2 mars 2022 par davidhxxx

common functions and variables

Functions to create or retrieve path objects

Create a path pointing to the current working directory (as returned by os.getcwd()) :
cwd: Path = Path.cwd()

Create a path by concatenating a Path with a String object:
– create a path relative to a foo path:
Example: 

cwd: Path = Path.cwd()
print(f'cwd={cwd}')
sub_dir: Path = cwd / '..' / 'foo/'
print(f'sub_dir={sub_dir}')

Output: 

cwd=C:\Users\david\AppData\Roaming\talon\helper_programs_for_talon
sub_dir=C:\Users\david\AppData\Roaming\talon\helper_programs_for_talon\..\foo

Beware: the created path object is in an unresolved state because of ..
As a consequence we cannot apply resolving functions on it such as relative_to()
– create a path child to a foo path:
file_path = foo_path / 'static_resources/file1.txt'

Create a path relative to another path

Here we work with Path objects and not String objects.
The 2 Path objects have to be absolute or relative but not a mix of them.
Example: 

base_dir: Path = Path.cwd() / 'fixtures/existing_images'
image_path = base_dir / 'image.jpg'
print(f'base_dir={base_dir}')
print(f'image_path={image_path}')
image_path_relative_to_base_dir = image_path.relative_to(base_dir)
print(f'image_path_relative_to_base_dir={image_path_relative_to_base_dir}')

output:

base_dir=C:\Users\david\AppData\Roaming\talon\helper_programs_for_talon\fixtures\existing_images
image_path=C:\Users\david\AppData\Roaming\talon\helper_programs_for_talon\fixtures\existing_images\image.jpg
image_path_relative_to_base_dir=image.jpg

Return a string representing the absolute file path of the current executed file:
__file__

create a path for this string:
path = Path(__file__)

Return a string representing the path separator for the current os
os.sep
Example: 

cwd: Path = Path.cwd()
print(f'cwd.parts={cwd.parts}')
joined_parts = os.sep.join(cwd.parts)
print(f'joined_parts={joined_parts}')
cwd.parts=('C:\\', 'Users', 'david', 'AppData', 'Roaming', 'talon', 'helper_programs_for_talon')
joined_parts=C:\\Users\david\AppData\Roaming\talon\helper_programs_for_talon

Functions to query path nature

check if a path exist:
path.exists()

check if a path is a file:
path.is_file()

check if a path is a directory:
path.is_dir()

Convert a Path into a String representing a Path and reversely

Path to String: 

cwd: Path = Path.cwd()
print(f'cwd={cwd}')
#cwd=C:\Users\david\AppData\Roaming\talon\helper_programs_for_talon
path_string: str = str(cwd)
print(f'path_string={path_string}')
#path_string=C:\Users\david\AppData\Roaming\talon\helper_programs_for_talon

String to Path : 

cwd : Path = Path(path_string)
print(f'cwd={cwd}')
#cwd=C:\Users\david\AppData\Roaming\talon\helper_programs_for_talon

Functions to query details of a Path objects

get the logical parent path of a path:
parent_path = foo_path.parent

Return a tuple representing the components in the filesystem path: parts attribute of the Path object.
Example: 

cwd: Path = Path.cwd()
print(f'cwd={cwd}')
print(f'cwd.parts={cwd.parts}')

Output: 

cwd=C:\Users\david\AppData\Roaming\talon\helper_programs_for_talon
cwd.parts=('C:\\', 'Users', 'david', 'AppData', 'Roaming', 'talon', 'helper_programs_for_talon')

Iterating on files and directories

The glob() function

A single instance method: Path.glob(pattern: str).
It returns a Generator of Paths.
We will see that with just that method we can cover most of cases.
Note:In the examples we will see now, we always use a list comprehension to store the result of iterations.
Of course, it is not an obligation. We do it because it is a common use case and besides it makes examples shorter than with classical loop iteration.

Iterating on files and directories (non recursive)from a specific path

foo_directory: Path = Path(r'D:\foo')
files_and_directories_of_foo: List[Path] = [p for p in foo_directory.glob('*')]

Iterating on files and directories recursively from a specific path

foo_directory: Path = Path(r'D:\foo')
deep_files_and_directories_of_foo: List[Path] = [p for p in foo_directory.glob('**/*')]

Filter Paths

Filter on files : 

files: List[Path] = [p for p in foo_directory.glob('**/*') if p.is_file()]

Filter on directories : 

directories: List[Path] = [p for p in foo_directory.glob('**/*') if p.is_dir()]

Filter on files with a specific extension (for example .bin extension): 

files: List[Path] = [p for p in foo_directory.glob('**/*.bin') if p.is_file()]

Filter on files with specific extensions : 

files: List[Path] = [p for p in foo_directory.glob('**/*') if p.is_file()  and p.suffix in {'.bin', '.py'}]

Create path object examples from distinct locations

in the following examples :
– the unit test class is tests/path_examples_test.py
– the existing file which we want to create a path object is static_resources/file1.txt
– sometimes we refer to create the path from another file/function, in this case, the functions called belong to that python file: files/path_examples.py

from pathlib import Path
 
from static_resources import stub as static_resources_stub
 
 
def load_a_file_from_module_path(file: str):
    mod_path = Path(__file__).parent.parent
    print(f'mod_path={mod_path}')
    return mod_path / file
 
 
def load_a_file_from_current_working_directory(file: str):
    return Path.cwd() / file
 
 
def load_a_file_from_specific_path(file: str):
    path = Path(static_resources_stub.__file__).parent / file
    return path

Create a path from current working directory

    def test_create_a_path_from_current_working_directory(self):
        cwd: Path = Path.cwd()
        file_path = cwd / '../static_resources/file1.txt'
        self.assertTrue(file_path.exists())
        self.assertTrue(file_path.is_file())
        # we can do it from another file also
        path = load_a_file_from_current_working_directory('../static_resources/file1.txt')
        self.assertTrue(path.exists())
        self.assertTrue(path.is_file())

Create a path from module path

    def test_create_a_path_from_module_path(self):
        path = Path(__file__).parent.parent / 'static_resources/file1.txt'
        self.assertTrue(path.exists())
        self.assertTrue(path.is_file())
        # we can do it from another file also(not that the parent path  is different according to the location of the file that creates the path)
        path = load_a_file_from_module_path('static_resources/file1.txt')
        self.assertTrue(path.exists())
        self.assertTrue(path.is_file())

Create a path from a specific path

    def test_create_a_path_from_a_specific_path(self):
        path = Path(static_resources_stub.__file__).parent / 'file1.txt'
        self.assertTrue(path.exists())
        self.assertTrue(path.is_file())
        # we can do it from another file also(not that the parent path  is different according to the location of the file that creates the path)
        path = load_a_file_from_specific_path('file1.txt')
        self.assertTrue(path.exists())
        self.assertTrue(path.is_file())
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