How to Safely Create a Nested Directory

How can I safely create a nested directory?

On Python ≥ 3.5, use pathlib.Path.mkdir:

from pathlib import Path
Path("/my/directory").mkdir(parents=True, exist_ok=True)

For older versions of Python, I see two answers with good qualities, each with a small flaw, so I will give my take on it:

Try os.path.exists, and consider os.makedirs for the creation.

import os
if not os.path.exists(directory):
    os.makedirs(directory)

As noted in comments and elsewhere, there's a race condition – if the directory is created between the os.path.exists and the os.makedirs calls, the os.makedirs will fail with an OSError. Unfortunately, blanket-catching OSError and continuing is not foolproof, as it will ignore a failure to create the directory due to other factors, such as insufficient permissions, full disk, etc.

One option would be to trap the OSError and examine the embedded error code (see Is there a cross-platform way of getting information from Python’s OSError):

import os, errno

try:
    os.makedirs(directory)
except OSError as e:
    if e.errno != errno.EEXIST:
        raise

Alternatively, there could be a second os.path.exists, but suppose another created the directory after the first check, then removed it before the second one – we could still be fooled.

Depending on the application, the danger of concurrent operations may be more or less than the danger posed by other factors such as file permissions. The developer would have to know more about the particular application being developed and its expected environment before choosing an implementation.

Modern versions of Python improve this code quite a bit, both by exposing FileExistsError (in 3.3+)...

try:
    os.makedirs("path/to/directory")
except FileExistsError:
    # directory already exists
    pass

...and by allowing a keyword argument to os.makedirs called exist_ok (in 3.2+).

os.makedirs("path/to/directory", exist_ok=True)  # succeeds even if directory exists.

How can create a nested directory?

Try this one for directory:

os.path.isdir(file_path)

To check if a file exist, try this:

os.path.isfile(file_path)

create nested folders in current directory in R?

This should do it:

cidr <- getwd()
mkfldr <- "test1/project/code/example"
dir.create(file.path(cidr, mkfldr), recursive = TRUE)

Create file along with nested directory in single command line

If I understand correctly and you simply want to be able to issue command foo/bar/baz/myfile.txt (or something similar) and have the directories foo/bar/baz created and a new file myfile.txt created and opened in nano all by that one command, then a short script is all you need, e.g.

Make it executable e.g. mv nanoopen.sh scriptname; chmod 0755 scriptname, then just call ./scriptname foo/bar/baz/file.txt. If you put it in your path, you can skip the ./ too.

The easy way to put it in your path is to create a symlink to it in /usr/local/bin which is generally in the default path.
So you could (sometime supersure is needed) ln -s /path/to/nanoopen.sh /usr/local/bin/scriptname. Echo $PATH to confirm /usr/local/bin is in your path, then just use it like any program, scriptname arguments.
Or in some distros you can simply add it to /bin folder with root access.

#!/bin/bash

[ -z "$1" ] && {  ## validate one argument given
    printf "error: insufficient input\nusage: %s filename\n" "${0##*/}"
    exit 1    
}

[ "$1" != "${1##*/}" ] && mkdir -p "${1%/*}"  ## if it has directories, create
touch "$1"                                    ## create the file

exec nano "$1"     ## open in nano

Example Use/Output

$ bash nanoopen.sh foo/bar/baz/main.c

$ tree foo/
foo/
└── bar
    └── baz
        └── main.c

$ cat foo/bar/baz/main.c
My new source!

Create nested dictionary from directory

instead of using the assignment operator here:

dict[key] = {x[:-4]: {'path': f'database/{x}'}}

call the update method on the dictionary:

dict[key].update({x[:-4]:{'path': f'database/{x}'}})

Check if Directory Exists, create nested directory

@Barmar Thank you for your help and patience!

I found were the problem lies.

def gen_subregion(srcimg, seg_image, trainimagefile, trainMaskfile, expandslice=5):
    # 5 get the roi range of mask,and expand number slices before and after,and get expand range roi image
    # for kinery
    startpostion, endpostion = getRangImageDepth(seg_image)
    if startpostion == endpostion:
        return
    imagez = np.shape(seg_image)[0]
    startpostion = startpostion - expandslice
    endpostion = endpostion + expandslice
    if startpostion < 0:
        startpostion = 0
    if endpostion > imagez:
        endpostion = imagez

    src_kineryimg = srcimg[startpostion:endpostion, :, :]
    seg_kineryimage = seg_image[startpostion:endpostion, :, :]
    # 6 write src, liver mask and tumor mask image
    for z in range(seg_kineryimage.shape[0]):
        src_kineryimg = np.clip(src_kineryimg, 0, 255).astype('uint8')
        cv2.imwrite(trainimagefile + "//" + str(z) + ".bmp", src_kineryimg[z])
        cv2.imwrite(trainMaskfile + "//" + str(z) + ".bmp", seg_kineryimage[z])

I had to change \\ to //.

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