Automatically creating directories with file output

Question

Say I want to make a file:

filename = "/foo/bar/baz.txt"

with open(filename, "w") as f:
    f.write("FOOBAR")

This gives an IOError, since /foo/bar does not exist.

What is the most pythonic way to generate those directories automatically? Is it necessary for me explicitly call os.path.exists and os.mkdir on every single one (i.e., /foo, then /foo/bar)?

score 865 · Accepted Answer · edited Jun 02 '22 at 17:56

865

COMMUNITY EDIT:
As question is closed, @David258's answer is written as a comment.

from pathlib import Path
output_file = Path("/foo/bar/baz.txt")
output_file.parent.mkdir(exist_ok=True, parents=True)
output_file.write_text("FOOBAR")

I leave it to the author of this answer to fold this in or remove it as they see fit.

Original answer starts here:

In Python 3.2+, you can elegantly do the following:


import os

filename = "/foo/bar/baz.txt"
os.makedirs(os.path.dirname(filename), exist_ok=True)
with open(filename, "w") as f:
    f.write("FOOBAR")

In older python, there is a less elegant way:

The os.makedirs function does this. Try the following:

import os
import errno

filename = "/foo/bar/baz.txt"
if not os.path.exists(os.path.dirname(filename)):
    try:
        os.makedirs(os.path.dirname(filename))
    except OSError as exc: # Guard against race condition
        if exc.errno != errno.EEXIST:
            raise

with open(filename, "w") as f:
    f.write("FOOBAR")

The reason to add the try-except block is to handle the case when the directory was created between the os.path.exists and the os.makedirs calls, so that to protect us from race conditions.

edited Jun 02 '22 at 17:56

P i

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answered Sep 20 '12 at 17:08

Krumelur

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2

Just had to look past `os.mkdir` and read the documentation on one more function :) – mgilson Sep 20 '12 at 17:09
8

There is a slightly different approach here: http://stackoverflow.com/a/14364249/1317713 Thoughts? – Leonid Apr 11 '16 at 06:02
2

Is the inital `if not os.path.exists` needed since the `os.makedirs` uses [EAFP](https://docs.python.org/2/glossary.html#term-eafp)? – Marcel Wilson Aug 16 '17 at 16:37
2

nice. but be aware you may need to check that the filename contains a path or attempting to create a path with an empty name (eg derived from `baz.txt`) will error `FileNotFoundError: [Errno 2] No such file or directory: ''` Obviously, this will only happen if you are writing into the present working directory. – ErichBSchulz Aug 06 '18 at 00:52
3

PermissionError: [Errno 13] Permission denied: '/foo' – Ka-Wa Yip Aug 17 '18 at 11:05
1

@Ka-WaYip `/foo/bar/baz.txt` is just an example. Replace it with the path you wish your file to be created. In linux, the command `pwd` gives you the path to the current working directory. – LoMaPh Sep 16 '19 at 16:55
9

with Pathlib: `from pathlib import Path; output_file = Path("/foo/bar/baz.txt"); output_file.parent.mkdir(exist_ok=True, parents=True); output_file.write_text("FOOBAR")` – David258 Jan 12 '21 at 12:46
@David258 Sorry they closed this question so you don't get any karma for your comment that's more useful now than the actual answer. But thanks. – Noumenon Sep 05 '21 at 16:26

Automatically creating directories with file output

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