How can I safely create a nested directory in Python?

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What is the most elegant way to check if the directory a file is going to be written to exists, and if not, create the directory using Python? Here is what I tried:

import os

file_path = "/my/directory/filename.txt"
directory = os.path.dirname(file_path)

try:
    os.stat(directory)
except:
    os.mkdir(directory)

f = file(filename)

Somehow, I missed os.path.exists (thanks kanja, Blair, and Douglas). This is what I have now:

def ensure_dir(file_path):
    directory = os.path.dirname(file_path)
    if not os.path.exists(directory):
        os.makedirs(directory)

Is there a flag for "open", that makes this happen automatically?

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How can I safely create a nested directory in Python? dirname: Questions

os.path.dirname(__file__) returns empty

2 answers

I want to get the path of the current directory under which a .py file is executed.

For example a simple file D: est.py with code:

import os

print os.getcwd()
print os.path.basename(__file__)
print os.path.abspath(__file__)
print os.path.dirname(__file__)

It is weird that the output is:

D:
test.py
D:	est.py
EMPTY

I am expecting the same results from the getcwd() and path.dirname().

Given os.path.abspath = os.path.dirname + os.path.basename, why

os.path.dirname(__file__)

returns empty?

174

Answer #1

Because os.path.abspath = os.path.dirname + os.path.basename does not hold. we rather have

os.path.dirname(filename) + os.path.basename(filename) == filename

Both dirname() and basename() only split the passed filename into components without taking into account the current directory. If you want to also consider the current directory, you have to do so explicitly.

To get the dirname of the absolute path, use

os.path.dirname(os.path.abspath(__file__))

How can I safely create a nested directory in Python? dirname: Questions

What is the difference between os.path.basename() and os.path.dirname()?

2 answers

What is the difference between os.path.basename() and os.path.dirname()?

I already searched for answers and read some links, but didn"t understand. Can anyone give a simple explanation?

158

Answer #1

Both functions use the os.path.split(path) function to split the pathname path into a pair; (head, tail).

The os.path.dirname(path) function returns the head of the path.

E.g.: The dirname of "/foo/bar/item" is "/foo/bar".

The os.path.basename(path) function returns the tail of the path.

E.g.: The basename of "/foo/bar/item" returns "item"

From: http://docs.python.org/3/library/os.path.html#os.path.basename

Python"s os.makedirs doesn"t understand "~" in my path

1 answers

I have a little problem with ~ in my paths.

This code example creates some directories called "~/some_dir" and do not understand that I wanted to create some_dir in my home directory.

my_dir = "~/some_dir"
if not os.path.exists(my_dir):
    os.makedirs(my_dir)

Note this is on a Linux-based system.

179

Answer #1

You need to expand the tilde manually:

my_dir = os.path.expanduser("~/some_dir")

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