dol.recipes

Recipes using dol

Functions

search_paths(pkv_filt, d, *[, leafs_only, ...])

Walk a dict, yielding paths to values that pass the pkv_filt
dol.recipes.search_paths(pkv_filt, d, *, leafs_only=True, breadth_first=False)[source]

Walk a dict, yielding paths to values that pass the pkv_filt

Parameters:

  • pkv_filt (Callable[[TypeVar(PT), TypeVar(KT), TypeVar(VT)], bool]) – A function that takes a path, key, and value, and returns True if the path should be yielded, and False otherwise

  • d (Mapping) – The Mapping to walk (scan through)

  • leafs_only (bool) – Whether to yield only paths to leafs (default), or to yield paths to all values that pass the pkv_filt.

  • breadth_first (bool) – Whether to perform breadth-first traversal (instead of the default depth-first traversal).

Return type:

Iterator[TypeVar(PT)]

Returns:

An iterator of paths to values that pass the pkv_filt

Example

>>> d = {'a': {'b': {'c': 1, 'd': 2}, 'e': 3}}
>>> list(path_filter(lambda p, k, v: v == 2, d))
[('a', 'b', 'd')]

>>> mm = {
...     'a': {'b': {'c': 42}},
...     'aa': {'bb': {'cc': 'meaning of life'}},
...     'aaa': {'bbb': 314},
... }
>>> return_path_if_int_leaf = lambda p, k, v: (p, v) if isinstance(v, int) else None
>>> paths = list(path_filter(return_path_if_int_leaf, mm))
>>> paths  # only the paths to the int leaves are returned
[('a', 'b', 'c'), ('aaa', 'bbb')]

The pkv_filt argument can use path, key, and/or value to define your search query. For example, let’s extract all the paths that have depth at least 3.

>>> paths = list(path_filter(lambda p, k, v: len(p) >= 3, mm))
>>> paths
[('a', 'b', 'c'), ('aa', 'bb', 'cc')]

The rationale for path_filter yielding matching paths, and not values or keys, is that if you have the paths, you can than get the keys and values with them, using path_get.

>>> from functools import partial, reduce
>>> path_get = lambda m, k: reduce(lambda m, k: m[k], k, m)
>>> extract_paths = lambda m, paths: map(partial(path_get, m), paths)
>>> vals = list(extract_paths(mm, paths))
>>> vals
[42, 'meaning of life']

Note

pkv_filt is first to match the order of the arguments of the builtin filter function.