TopolearnScripts constantly need to know whether an input exists and what files a folder holds.
These methods ask the file system:
p.exists()true if anything is there (following symlinks)p.is_file(),p.is_dir(),p.is_symlink()p.stat().st_sizesize in bytes,p.stat().st_mtimemodification time
They return False rather than raising when the path is missing or inaccessible. Since 3.12, exists, is_file and is_dir take follow_symlinks=False to inspect links themselves.
p.iterdir() yields a Path for each entry in the directory, already joined with p, in arbitrary order. Unlike os.listdir, you get usable paths, not bare names:
csvs = sorted(f for f in folder.iterdir() if f.suffix == ".csv")iterdir raises NotADirectoryError if p is a file and FileNotFoundError if it's missing.
Checking before acting is fine for user-facing messages ("input file not found"), but for correctness it can race: the file can vanish between exists() and read_text(). When it matters, just attempt the operation and catch FileNotFoundError.
For recursive listings, use glob/rglob or Path.walk() instead of nesting iterdir calls by hand.
Example
from pathlib import Path
folder = Path("inbox")
folder.mkdir()
for name in ["b.csv", "a.csv", "readme.md"]:
(folder / name).write_text("x", encoding="utf-8")
(folder / "archive").mkdir()
print(folder.exists(), folder.is_dir()) # True True
print(sorted(p.name for p in folder.iterdir())) # ['a.csv', 'archive', 'b.csv', 'readme.md']
csvs = sorted(p for p in folder.iterdir() if p.is_file() and p.suffix == ".csv")
print(csvs) # [PosixPath('inbox/a.csv'), PosixPath('inbox/b.csv')]
print((folder / "nope.txt").exists()) # False
print((folder / "a.csv").stat().st_size) # 1Remember
exists,is_fileandis_dirreturn False instead of raisingiterdir()yields full Path objects in arbitrary order- Prefer try/except over check-then-act when correctness matters
Watch out for
- Sorting by assuming iterdir returns alphabetical order; it doesn't.