Creating, renaming and deleting

Setup and cleanup code (output folders, temp files, rotations) depends on getting these calls and their errors right.

Directories:

os.mkdir(p) creates one directory and fails if the parent is missing or p exists.
os.makedirs(p, exist_ok=True) creates all missing parents and does nothing if p already exists. This is the idiom for "ensure the output folder exists".
os.rmdir(p) removes an empty directory; os.removedirs also removes empty parents.
For a non-empty tree, use shutil.rmtree(p). It deletes without asking, so double-check the path.

Files:

os.remove(p) (alias os.unlink) deletes a file. It raises IsADirectoryError or PermissionError for a directory, depending on the platform.
os.rename(src, dst) renames or moves within one file system. On Windows it fails if dst exists.
os.replace(src, dst) does the same but overwrites dst on every platform, and on POSIX the swap is atomic.
To move across file systems or copy, use shutil.move and shutil.copy2.

Errors are specific OSError subclasses: FileExistsError, FileNotFoundError, PermissionError, IsADirectoryError, NotADirectoryError. Catch the one you expect rather than a bare OSError, and prefer "try it and handle the error" over checking exists first, which races with other processes.

Example

import os
import shutil

os.makedirs("out/2024/q1", exist_ok=True)
os.makedirs("out/2024/q1", exist_ok=True)   # no error the second time
with open("out/draft.txt", "w") as f:
    f.write("v1")

os.replace("out/draft.txt", "out/final.txt")  # overwrite-safe rename
print(sorted(os.listdir("out")))  # ['2024', 'final.txt']

try:
    os.rmdir("out")               # not empty
except OSError as e:
    print(type(e).__name__)       # OSError

os.remove("out/final.txt")
shutil.rmtree("out")              # whole tree
print(os.path.exists("out"))      # False

Remember

os.makedirs(p, exist_ok=True) is the safe way to ensure a folder
os.replace overwrites and is atomic on POSIX; os.rename may fail on Windows
Use shutil.rmtree/shutil.move for whole trees and cross-device moves

Watch out for

Checking os.path.exists and then creating; another process can win the race, so use exist_ok=True or catch FileExistsError.

Check yourself

You need to save a file to out/reports/2024/ and none of these folders exist yet. Which call prepares them?

Official docs: docs.python.org/3/library/os.html#os.makedirs

Example

Remember

Watch out for

Check yourself

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