Path Strings

Note

Source: Adapted from the C# edition (files/paths.rst). Python uses plain strings or pathlib.Path objects instead of C#’s System.IO.Path class. Cross-platform separator differences are the same, but Python’s pathlib handles them transparently.

When a program runs there is always a current working directory. Files in that directory can be opened by their plain name, like "data.txt". Files elsewhere require a path string — a chain of directory names leading to the target file.

Absolute and Relative Paths

An absolute path starts from the root of the file system:

/Users/alice/Documents/data.txt       (macOS / Linux)
C:\Users\alice\Documents\data.txt     (Windows)

A relative path starts from the current working directory and does not begin with a separator:

data.txt                  (file in the current directory)
reports/summary.txt       (subdirectory of the current directory)
../other_project/run.py   (one level up, then into another folder)

.. means “the parent directory”; . means “the current directory.”

Cross-Platform Path Separators

Windows uses \ and macOS/Linux use /. Hard-coding either character makes scripts fragile. Python’s pathlib module handles this automatically using the / operator to join path components:

from pathlib import Path

p = Path("reports") / "2024" / "summary.txt"
print(p)

Output (macOS/Linux):

reports/2024/summary.txt

The / operator always uses the correct separator for the current OS.

Finding the Current Directory

from pathlib import Path

print(Path.cwd())    # current working directory
print(Path.home())   # user's home directory

Output (example):

/Users/alice/projects/myapp
/Users/alice

Full details on working with Path objects — reading attributes, checking existence, and listing directories — are in Working with pathlib.