Walking a filesystem means recursively visiting a directory and any sub-directories. It is a fairly common requirement for copying, searching etc.

To walk a filesystem (or directory) you can construct a Walker object and use its methods to do the walking. Here’s an example that prints the path to every Python file in your projects directory:

>>> from fs import open_fs
>>> from fs.walk import Walker
>>> home_fs = open_fs('~/projects')
>>> walker = Walker(filter=['*.py'])
>>> for path in walker.files(home_fs):
...     print(path)

Generally speaking, however, you will only need to construct a Walker object if you want to customize some behavior of the walking algorithm. This is because you can access the functionality of a Walker object via the walk attribute on FS objects. Here’s an example:

>>> from fs import open_fs
>>> home_fs = open_fs('~/projects')
>>> for path in home_fs.walk.files(filter=['*.py']):
...     print(path)

Note that the files method above doesn’t require a fs parameter. This is because the walk attribute is a property which returns a BoundWalker object, which associates the filesystem with a walker.

Walk Methods

If you call the walk attribute on a BoundWalker it will return an iterable of Step named tuples with three values; a path to the directory, a list of Info objects for directories, and a list of Info objects for the files. Here’s an example:

for step in home_fs.walk(filter=['*.py']):
    print('In dir {}'.format(step.path))
    print('sub-directories: {!r}'.format(step.dirs))
    print('files: {!r}'.format(step.files))


Methods of BoundWalker invoke a corresponding method on a Walker object, with the bound filesystem.

The walk attribute may appear to be a method, but is in fact a callable object. It supports other convenient methods that supply different information from the walk. For instance, files(), which returns an iterable of file paths. Here’s an example:

for path in home_fs.walk.files(filter=['*.py']):
    print('Python file: {}'.format(path))

The compliment to files is dirs() which returns paths to just the directories (and ignoring the files). Here’s an example:

for dir_path in home_fs.walk.dirs():
    print("{!r} contains sub-directory {}".format(home_fs, dir_path))

The info() method returns a generator of tuples containing a path and an Info object. You can use the is_dir attribute to know if the path refers to a directory or file. Here’s an example:

for path, info in home_fs.walk.info():
    if info.is_dir:
        print("[dir] {}".format(path))
        print("[file] {}".format(path))

Finally, here’s a nice example that counts the number of bytes of Python code in your home directory:

bytes_of_python = sum(
    for info in home_fs.walk.info(namespaces=['details'])
    if not info.is_dir

Search Algorithms

There are two general algorithms for searching a directory tree. The first method is “breadth”, which yields resources in the top of the directory tree first, before moving on to sub-directories. The second is “depth” which yields the most deeply nested resources, and works backwards to the top-most directory.

Generally speaking, you will only need the a depth search if you will be deleting resources as you walk through them. The default breadth search is a generally more efficient way of looking through a filesystem. You can specify which method you want with the search parameter on most Walker methods.