I'm using Python to parse a WordPress site downloaded via wget. All the HTML files are nested inside a complicated folder structure (thanks to WordPress and its long URLs), like site_dump/2010/03/11/post-title/index.html.
However, within the post-title directory there are other directories for the feed and for Google News-esque number-based indexes:
site_dump/2010/03/11/post-title/index.html # I want this
site_dump/2010/03/11/post-title/feed/index.html # Not these
site_dump/2010/03/11/post-title/115232/site.com/2010/03/11/post-title/index.html
I only want to access the index.html files that are at the 5th nested level (site_dump/2010/03/11/post-title/index.html), and not beyond. Right now I split the root variable by a slash (/) in the os.walk loop and only deal with the file if it is inside 5 levels of folders:
import os
for root, dirs, files in os.walk('site_dump'):
nested_levels = root.split('/')
if len(nested_levels) == 5:
print(nested_levels) # Eventually do stuff with the file here
However, this seems kind of inefficient, since os.walk is still traversing those really deep folders. Is there a way to limit how deep os.walk goes when traversing a directory tree?
You can modify dirs in place to prevent further traversal into the directory structure.
for root, dirs, files in os.walk('site_dump'):
nested_levels = root.split('/')
if len(nested_levels) == 5:
del dirs[:]
# Eventually do stuff with the file here
del dirs[:] will remove the contents of the list, rather than replace dirs with a reference to a new list. When doing this it is important to modify the list in-place.
From the docs, with topdown referring to an optional parameter for os.walk that you omitted and defaults to True:
When topdown is True, the caller can modify the dirnames list in-place
(perhaps using del or slice assignment), and walk() will only recurse
into the subdirectories whose names remain in dirnames; this can be
used to prune the search, impose a specific order of visiting, or even
to inform walk() about directories the caller creates or renames
before it resumes walk() again. Modifying dirnames when topdown is
False is ineffective, because in bottom-up mode the directories in
dirnames are generated before dirpath itself is generated.
Related
I’m looking (in Python 3) for a cross-platform way to get a list of all the file and folder paths within a folder, similar to what I would get with pexpect.run(“find /media/elon/SuperDrive/*”).splitlines() on Linux. Is there already a function to do this, say, somewhere in shutil or glob? I could write my own function, but I figured there might be something pre-built that could possibly do it quicker than my code could.
The walk function in the native module os does this nicely.
Help on function walk in module os:
walk(top, topdown=True, onerror=None, followlinks=False)
Directory tree generator.
For each directory in the directory tree rooted at top (including top
itself, but excluding '.' and '..'), yields a 3-tuple
dirpath, dirnames, filenames
dirpath is a string, the path to the directory. dirnames is a list of
the names of the subdirectories in dirpath (excluding '.' and '..').
filenames is a list of the names of the non-directory files in dirpath.
Note that the names in the lists are just names, with no path components.
To get a full path (which begins with top) to a file or directory in
dirpath, do os.path.join(dirpath, name).
If optional arg 'topdown' is true or not specified, the triple for a
directory is generated before the triples for any of its subdirectories
(directories are generated top down). If topdown is false, the triple
for a directory is generated after the triples for all of its
subdirectories (directories are generated bottom up).
When topdown is true, the caller can modify the dirnames list in-place
(e.g., via del or slice assignment), and walk will only recurse into the
subdirectories whose names remain in dirnames; this can be used to prune the
search, or to impose a specific order of visiting. Modifying dirnames when
topdown is false has no effect on the behavior of os.walk(), since the
directories in dirnames have already been generated by the time dirnames
itself is generated. No matter the value of topdown, the list of
subdirectories is retrieved before the tuples for the directory and its
subdirectories are generated.
By default errors from the os.scandir() call are ignored. If
optional arg 'onerror' is specified, it should be a function; it
will be called with one argument, an OSError instance. It can
report the error to continue with the walk, or raise the exception
to abort the walk. Note that the filename is available as the
filename attribute of the exception object.
By default, os.walk does not follow symbolic links to subdirectories on
systems that support them. In order to get this functionality, set the
optional argument 'followlinks' to true.
Caution: if you pass a relative pathname for top, don't change the
current working directory between resumptions of walk. walk never
changes the current directory, and assumes that the client doesn't
either.
Example:
import os
from os.path import join, getsize
for root, dirs, files in os.walk('python/Lib/email'):
print(root, "consumes", end="")
print(sum(getsize(join(root, name)) for name in files), end="")
print("bytes in", len(files), "non-directory files")
if 'CVS' in dirs:
dirs.remove('CVS') # don't visit CVS directories
I need to stop os.walk from going down further if the path contains both "release" and "arm-linux". I have a bunch of these at different levels of directories. So I can't simply dictate the level. So far I have the following and it unnecessarily dive past directories in 'arm-linux'.
def main(argv):
for root, dirs, files in os.walk("."):
path = root.split(os.sep)
if "release" and "arm-linux" in path:
print(os.path.abspath(root))
getSharedLib(argv)
[update] This is my solution
def main(argv):
for root, dirs, files in os.walk("."):
path = root.split(os.sep)
if "release" in path and "arm-linux" in path:
print(os.path.abspath(root))
getSharedLib(argv)
del dirs[:]
From the documentation
When topdown is True, the caller can modify the dirnames list in-place (perhaps using del or slice assignment), and walk() will only recurse into the subdirectories whose names remain in dirnames;
Note that topdown is True by default.
Edit
To delete all the elements of dirs, you will need something like del dirs[:]. That will delete all the elements of the list object that is referred to as dirs in your code, but is referred to by another name in the os.walk code.
Just using del dirs will stop dirs in your code from referring to the list, but won't do anything to the os.walk reference. Similarly dirs = [] will replace what dirs in your code refers to, but won't affect os.walk code.
I need to list all files with the containing directory path inside a folder. I tried to use os.walk, which obviously would be the perfect solution.
However, it also lists hidden folders and files. I'd like my application not to list any hidden folders or files. Is there any flag you can use to make it not yield any hidden files?
Cross-platform is not really important to me, it's ok if it only works for linux (.* pattern)
No, there is no option to os.walk() that'll skip those. You'll need to do so yourself (which is easy enough):
for root, dirs, files in os.walk(path):
files = [f for f in files if not f[0] == '.']
dirs[:] = [d for d in dirs if not d[0] == '.']
# use files and dirs
Note the dirs[:] = slice assignment; os.walk recursively traverses the subdirectories listed in dirs. By replacing the elements of dirs with those that satisfy a criteria (e.g., directories whose names don't begin with .), os.walk() will not visit directories that fail to meet the criteria.
This only works if you keep the topdown keyword argument to True, from the documentation of os.walk():
When topdown is True, the caller can modify the dirnames list in-place (perhaps using del or slice assignment), and walk() will only recurse into the subdirectories whose names remain in dirnames; this can be used to prune the search, impose a specific order of visiting, or even to inform walk() about directories the caller creates or renames before it resumes walk() again.
I realize it wasn't asked in the question, but I had a similar problem where I wanted to exclude both hidden files and files beginning with __, specifically __pycache__ directories. I landed on this question because I was trying to figure out why my list comprehension was not doing what I expected. I was not modifying the list in place with dirnames[:].
I created a list of prefixes I wanted to exclude and modified the dirnames in place like so:
exclude_prefixes = ('__', '.') # exclusion prefixes
for dirpath, dirnames, filenames in os.walk(node):
# exclude all dirs starting with exclude_prefixes
dirnames[:] = [dirname
for dirname in dirnames
if not dirname.startswith(exclude_prefixes)]
My use-case was similar to that of OP, except I wanted to return a count of the total number of sub-directories inside a certain folder. In my case I wanted to omit any sub-directories named .git (as well as any folders that may be nested inside these .git folders).
In Python 3.6.7, I found that the accepted answer's approach didn't work -- it counted all .git folder and their sub-folders. Here's what did work for me:
num_local_subdir = 0
for root, dirs, files in os.walk(local_folder_path):
if '.git' in dirs:
dirs.remove('.git')
num_local_subdir += (len(dirs))
Another solution that can allow you to skip those hidden folders using any and map functions.
for root, dirs, files in os.walk(path):
if any(map(lambda p: p[0] == '.', dirs)):
continue
I need to list all files with the containing directory path inside a folder. I tried to use os.walk, which obviously would be the perfect solution.
However, it also lists hidden folders and files. I'd like my application not to list any hidden folders or files. Is there any flag you can use to make it not yield any hidden files?
Cross-platform is not really important to me, it's ok if it only works for linux (.* pattern)
No, there is no option to os.walk() that'll skip those. You'll need to do so yourself (which is easy enough):
for root, dirs, files in os.walk(path):
files = [f for f in files if not f[0] == '.']
dirs[:] = [d for d in dirs if not d[0] == '.']
# use files and dirs
Note the dirs[:] = slice assignment; os.walk recursively traverses the subdirectories listed in dirs. By replacing the elements of dirs with those that satisfy a criteria (e.g., directories whose names don't begin with .), os.walk() will not visit directories that fail to meet the criteria.
This only works if you keep the topdown keyword argument to True, from the documentation of os.walk():
When topdown is True, the caller can modify the dirnames list in-place (perhaps using del or slice assignment), and walk() will only recurse into the subdirectories whose names remain in dirnames; this can be used to prune the search, impose a specific order of visiting, or even to inform walk() about directories the caller creates or renames before it resumes walk() again.
I realize it wasn't asked in the question, but I had a similar problem where I wanted to exclude both hidden files and files beginning with __, specifically __pycache__ directories. I landed on this question because I was trying to figure out why my list comprehension was not doing what I expected. I was not modifying the list in place with dirnames[:].
I created a list of prefixes I wanted to exclude and modified the dirnames in place like so:
exclude_prefixes = ('__', '.') # exclusion prefixes
for dirpath, dirnames, filenames in os.walk(node):
# exclude all dirs starting with exclude_prefixes
dirnames[:] = [dirname
for dirname in dirnames
if not dirname.startswith(exclude_prefixes)]
My use-case was similar to that of OP, except I wanted to return a count of the total number of sub-directories inside a certain folder. In my case I wanted to omit any sub-directories named .git (as well as any folders that may be nested inside these .git folders).
In Python 3.6.7, I found that the accepted answer's approach didn't work -- it counted all .git folder and their sub-folders. Here's what did work for me:
num_local_subdir = 0
for root, dirs, files in os.walk(local_folder_path):
if '.git' in dirs:
dirs.remove('.git')
num_local_subdir += (len(dirs))
Another solution that can allow you to skip those hidden folders using any and map functions.
for root, dirs, files in os.walk(path):
if any(map(lambda p: p[0] == '.', dirs)):
continue
I am working on a backup script in Python, and would like it to be able to ignore folders. I therefore have a list of folders to be ignored, ie ['Folder 1', 'Folder3']. I am using os.walk, and am trying to get it to skip any folder in the ignored folders list or that has any of the ignored folders as a parent directory. Has anyone done this before, as examples I've seen don't seem to work and often end up creating an empty folder?
From the docs:
When topdown is True, the caller can modify the dirnames list in-place (perhaps using del or slice assignment), and walk() will only recurse into the subdirectories whose names remain in dirnames; this can be used to prune the search, impose a specific order of visiting, or even to inform walk() about directories the caller creates or renames before it resumes walk() again.
So, iterate through your list and remove entries that match.
After the following statement
folders = [path+'/'+dir for (path,dirs,files) in os.walk(base)
for dir in dirs
if dir not in ['Folder 1', 'Folder3', ...]]
the variable folders should contain the folders you are interested in.
Edit1: ... + '/' + ... works just in Unix-like OS. I think there is a os.path.join which does the same job platform indepentently
Edit2: If you want to exclude all Subdirectories of the directories to be excluded, you can try the following:
exclusions = ['Folder 1', 'Folder3', ...]
folders = [path+'/'+dir for (path,dirs,files) in os.walk(base)
if not any([f in path for f in exclusions])
for dir in dirs
if dir not in exclusions
]