draversal 0.1.5

A package for depth-first traversal of Python dictionaries with uniform child fields, supporting both forward and backward navigation.

draversal

A package for depth-first traversal of Python dictionaries with uniform child fields, supporting both forward and backward navigation.

---

DOCUMENTATION WITH EXAMPLES

Class: DictSearchQuery

Description

Provides utilities for querying nested dictionaries based on various conditions.

Attributes

• OPERATOR_MAP (dict): A mapping of query operators to Python's operator functions.
• query (dict): The query to execute against the data.
• support_wildcards (bool): Flag to enable wildcard support in queries.
• support_regex (bool): Flag to enable regular expression support in queries.

Behavior

• Initializes with a query and optional flags for supporting wildcards and regular expressions.
• Provides methods to match keys based on different conditions like wildcards, regular expressions, and exact matches.
• Executes the query on a nested dictionary and returns the matched fields.

Example

query = {'a.b.c': 1}
dsq = DictSearchQuery(query)
data = {'a': {'b': {'c': 1}}, 'd': [ {'e': 2}, {'f': 3, 'g': 4} ]}
result = dsq.execute(data)
print(result)  # Outputs: {'c': 1}

---

Class: DictTraversal

Description

Depth-first traverse Python dictionary with a uniform children (and label) field structure.

Class initialization takes a dictionary data argument and a mandatory children field which must correspond to the dictionary children list field. Optionally data can be provided as keyword arguments.

Except from child field, all other fields are optional and the rest of the dictionary can be formed freely.

Example

children_field = 'sections'
data = {
    'title': 'root',
    children_field: [
        {'title': 'Child 1'},
        {'title': 'Child 2', children_field: [
            {'title': 'Grandchild 1'},
            {'title': 'Grandchild 2', children_field: [
                {'title': 'Grandgrandchild'}
            ]}
        ]},
        {'title': 'Child 3'}
    ]
}
traversal = DictTraversal(data, children_field=children_field)
# If you want to validate that data has expected and required fields
# with a correct nested structure, you can use validate_data function:
try:
    validate_data(data, children_field, 'title')
    print('Given data is valid.')
except ValueError as e:
    print(f'Given data is invalid. {e}')

After initialization, a certain methods are available for traversing and modifying the nested tree structure.

(
    # Iter function brings to the root, from which the traversal starts,
    # but actually the first items has not been reached yet
    print(iter(traversal)),  # Outputs: {'title': 'root'}
    # Next function forwards iterator to the first/next item. In this case it is the root.
    # It yields StopIteration error when the end of the tree has been reached.
    print(next(traversal)),  # Outputs: {'title': 'root'}
    # Prev function works similar way and it yields StopIteration error,
    # when the beginning of the tree has been reached.
    print(prev(next(next(traversal)))),  # Outputs: {'title': 'Child 1'}
    # First function brings to the first item in the list (after root).
    print(first(traversal)),  # Outputs: {'title': 'Child 1'}
    # Root function brings to the root, from which the traversal starts.
    # Next item will be first item contra to iter which will give root as
    # the first item only after calling next.
    print(root(traversal))  # Outputs: {'title': 'root'}
    # Last function brings to the last item in the list.
    print(last(traversal)),  # Outputs: {'title': 'Child 3'}
)

Root is a special place in a tree. When `DictTraversal` has been initialized, or `iter`/`root` functions are called,
root is a starting point of the tree, which contains the first siblings. To traverse to the first sibling,
either next, first, or move_to_next_item methods must be called.

__Other operations__

```python
# Count the number of all children for the current node
print(traversal.count_children())  # Outputs: 6

# Get the last item in the tree
print(traversal.get_last_item())  # Outputs: {'title': 'Child 3'}

# Search for nodes with a specific title
result = traversal.search('Child 1', label_field='title')
print(result)  # Outputs: [({'title': 'Child 1'}, [0]), ({'title': 'Grandchild 1'}, [1, 0])]

# Add a new child to the current node
traversal.add_child(title='New Child')

# Visualize the tree structure
print(traversal.visualize(label_field='title'))  # Outputs:
# root*
# ├── Child 1
# ├── Child 2
# │   ├── Grandchild 1
# │   └── Grandchild 2
# │└── Grandgrandchild
# ├── Child 3
# └── New Child
```

There are a plenty of methods that can be used to further navigate, search, add/modify/remove items and visualize the tree.
This is a short list to them. Please refer to the method docs for further information.

```
demo() -> DictTraversal
first(traversal) -> self
last(traversal) -> self
prev(traversal) -> self/StopIteration
root(traversal) -> self
validate_data(data, children_field, label_field=None) -> None/ValueError
__delitem__(idx) -> self/IndexError/ValueError
__getitem__(idx) -> any/IndexError/ValueError
__init__(*args, children_field=None, **kwargs) -> DictTraversal
__invert__() -> self
__iter__() -> self
__len__() -> int
__neg__() -> self
__next__() -> self/StopIteration
__pos__() -> self
__repr__() -> str
add_child(*idx, **kwargs) -> self
children(sibling_only=False) -> list
count_children(sibling_only=False) -> int
find_paths(label_field, titles) -> list(tuple(dict, list),...)
get_item_by_path(path) -> dict
get_last_item(sibling_only=False) -> dict
get_last_item_and_path(sibling_only=False) -> tuple(dict, list)
get_last_path(sibling_only=False) -> list
get_next_item_and_path(sibling_only=False) -> tuple(dict, list)
get_parent_item() -> dict
get_parent_item_and_path(with_children=False) -> tuple(dict, list)
get_parent_path() -> list
get_previous_item_and_path(sibling_only=False) -> tuple(dict, list)
insert_child(idx, **kwargs) -> self
@contextmanager inverted() -> DictTraversal
max_depth() -> int
modify(key=None, value=None, **kwargs) -> self
move_to_next_item(sibling_only=False) -> self
move_to_prev_item(sibling_only=False) -> self
@contextmanager new_root(merge=False) -> DictTraversal
peek_next(steps=1) -> dict
peek_prev(steps=1) -> dict
pretty_print(label_field=None) -> None
replace_child(idx, **kwargs) -> self
search(query, label_field=None) -> list(tuple(dict, list),...)
set_last_item_as_current(sibling_only=False) -> self
set_parent_item_as_current() -> self
set_path_as_current(path) -> self
visualize(label_field=None, from_root=False) -> str
```

---

Method: demo

Description

Initializes and returns a DictTraversal object with sample data.

Behavior

• Creates a nested dictionary structure with title and sections fields.
• Initializes a DictTraversal object with the sample data.

Example

traversal = demo()
traversal.pretty_print()  # Outputs:
# root
#   Child 1
#   Child 2
#     Grandchild 1
#     Grandchild 2
#       Grandgrandchild
#   Child 3

---

Method: first

Description

Moves the traversal to the first item relative to the root.

Parameters

• traversal (DictTraversal): The DictTraversal object to operate on.

Behavior

• Moves the traversal to the first item in the tree, updating the current attribute.

Example

first(traversal)  # Returns: {'title': 'Child 1'}

---

Method: flatten_dict

Description

Flattens a nested dictionary into a single-level dictionary.

Parameters

• data (dict): The nested dictionary to flatten.
• field_separator (str, optional): The separator for nested keys. Defaults to '.'.
• list_index_indicator (str, optional): The format string for list indices. Defaults to '#%s'.

Behavior

• Recursively traverses the nested dictionary and flattens it.
• Handles nested dictionaries and lists of dictionaries.

Example

nested_dict = {'a': {'b': {'c': 1}}, 'd': [ {'e': 2}, {'f': 3, 'g': 4} ]}
flat_dict = flatten_dict(nested_dict)
print(flat_dict)  # Outputs: {'a.b.c': 1, 'd#0.e': 2, 'd#1.f': 3, 'd#1.g': 4}

flat_dict = flatten_dict(nested_dict, list_index_indicator='[%s]')
print(flat_dict)  # Outputs: {'a.b.c': 1, 'd[0].e': 2, 'd[1].f': 3, 'd[1].g': 4}

---

Method: last

Description

Moves the traversal to the last item from the current item perspective.

Parameters

• traversal (DictTraversal): The DictTraversal object to operate on.

Behavior

• Moves the traversal to the last item in the tree, updating the current attribute.

Example

last(traversal)  # Returns: {'title': 'Child 3'}
# Calling the end item, same will be returned
last(traversal)  # Returns: {'title': 'Child 3'}

---

Method: prev

Description

Moves the traversal to the previous item relative to the current item.

Parameters

• traversal (DictTraversal): The DictTraversal object to operate on.

Raises

• StopIteration: If there are no more items to traverse in the backward direction.

Behavior

• Updates the current attribute to point to the previous item in the tree.
• Influenced by the inverted context manager.

Note

• Serves as a counterpart to Python's built-in next function.
• Does not support a siblings_only argument; use move_to_next_item or move_to_prev_item directly for that.
• Unlike move_to_next_item and move_to_prev_item, which cycle through the tree, prev raises StopIteration when reaching the end.

Example

# With default context
last(traversal)
try:
    print(traversal['title'])  # Output: Grandgrandchild
    prev(traversal)
    print(traversal['title'])  # Output: Grandchild 2
except StopIteration:
    print('No more items to traverse.')

# With inverted context
last(traversal)
with traversal.inverted():
    try:
        print(traversal['title'])  # Output: Grandgrandchild
        prev(traversal)
        print(traversal['title'])  # Output: Child 3
    except StopIteration:
        print('No more items to traverse.')

---

Method: reconstruct_item

Description

Reconstructs an item from a nested dictionary based on a flattened query key.

Parameters

• query_key (str): The query key to use for reconstruction.
• item (dict): The nested dictionary.
• field_separator (str, optional): The separator for nested keys. Defaults to '.'.
• list_index_indicator (str, optional): The indicator for list indices. Defaults to '#%s'.

Behavior

• Splits the query key using field_separator and list_index_indicator.

• Traverses the flattened dictionary to reconstruct the original nested structure.

• If the query key ends with a list index indicator (e.g., '#0'), the function returns the item at that index in the list.

• If the query key ends with a regular key, the function returns a dictionary containing that key and its corresponding value.

  List Index Indicator:

• The list_index_indicator is used to specify indices in lists within the nested dictionary.

• The default indicator is '#%s', where '%s' is a placeholder for the index number.

• The indicator can be customized. For example, using '[%s]' would allow list indices to be specified like 'd[0].e'.

Example

data = {'a': {'b': {'c': 1}}, 'd': [{'e': 2}, {'f': 3, 'g': 4}]}
print(reconstruct_item('a.b.c', data))  # Outputs: {'c': 1}
print(reconstruct_item('a.b', data))  # Outputs: {'b': {'c': 1}}
print(reconstruct_item('a', data))  # Outputs: {'a': {'b': {'c': 1}}}

print(reconstruct_item('d#0.e', data))  # Outputs: {'e': 2}
print(reconstruct_item('d#1', data))  # Outputs: {'f': 3, 'g': 4}

print(reconstruct_item('d[0].e', data, list_index_indicator='[%s]'))  # Outputs: {'e': 2}
print(reconstruct_item('d[1]', data, list_index_indicator='[%s]'))  # Outputs: {'f': 3, 'g': 4}

---

Method: root

Description

Resets the traversal to the root item.

Parameters

• traversal (DictTraversal): The DictTraversal object to operate on.

Behavior

• Resets the traversal to the root item, updating the current attribute.

Example

root(traversal)  # Returns: {'title': 'root'}

---

Method: translate

Description

Translate a shell PATTERN to a regular expression.

There is no way to quote meta-characters.

---

Method: validate_data

Description

Validates a nested dictionary structure for specific field requirements.

Parameters

• data (dict): The nested dictionary to validate.
• children_field (str): The field name that contains child dictionaries.
• label_field (str, optional): The field name that should exist in each dictionary, including the root.

Raises

• ValueError: If any of the validation conditions are not met.

Behavior

• Validates that the root is a non-empty dictionary.
• Validates that the children_field exists in the root if label_field is not provided.
• Validates that label_field exists in each nested dictionary, if specified.
• Validates that each children_field is a list.
• Validates that each child in children_field is a non-empty dictionary.

Example

try:
    validate_data({'title': 'root', 'sections': [{'title': 'Child'}]}, 'sections', 'title')
    print('Given data is valid.')
except ValueError as e:
    print(f'Given data is invalid. {e}')

---

Method: DictTraversal.__delitem__

Description

Deletes an item based on the given index.

Parameters

• idx (int, slice, tuple, list, str): The index to delete the item.

Attributes

• current (dict): The current item in the traversal, updated after deletion.

Raises

• IndexError: If children are not found at the given index.
• ValueError: If index type is not supported.

Behavior

• If index is an int or slice, deletes child items from the current item.
• If index is a tuple or list, traverses the nested children to delete the item.
• If index is a string, deletes the corresponding attribute in the current item.

Example

del obj[0]  # Deletes the first child of the current item
del traversal[(0, 0)]  # Deleted the first child of the first child of the current item
del traversal[1:2]  # Deleted the second and third children of the current item
del obj['name']  # Deletes the name attribute of the current item

---

Method: DictTraversal.__getitem__

Description

Retrieves an item based on the given index.

Parameters

• idx (int, slice, tuple, list, str): The index to retrieve the item.

Attributes

• current (dict): The current item in the traversal.
• children_field (str): The key used to identify children in the dictionary.

Raises

• IndexError: If children are not found at the given index.
• ValueError: If index type is not supported.

Behavior

• If index is an int or slice, retrieves child items from the current item.
• If index is a tuple or list, traverses the nested children to retrieve the item.
• If index is a string, retrieves the value of the corresponding attribute in the current item.

Example

item = traversal[0]  # Retrieves the first child of the current item
item = traversal[(0, 0)]  # Retrieves the first child of the first child of the current item
items = traversal[1:2]  # Retrieves the second and third children of the current item
item = traversal['name']  # Retrieves the name attribute of the current item

---

Method: DictTraversal.__init__

Description

Initializes the DictTraversal object.

Parameters

• *args (list): Variable-length argument list to initialize the dictionary.
• children_field (str): The key used to identify children in the dictionary.
• **kwargs (dict): Arbitrary keyword arguments to initialize the dictionary.

Attributes

• children_field (str): The key used to identify children in the dictionary.
• path (list): Keeps track of the traversal path.
• current (dict): Points to the current item in the traversal.
• iter_method (func): Function used for moving to the next/previous item during iteration.
• next_iteration_start (bool): Flag used to control the behavior of __iter__()/__next__().
• prev_iteration_stop (bool): Flag used to control the behavior of __iter__()/prev().
• inverted_context (bool): Flag to indicate whether the iteration context ie. direction manipulated by with is inverted or not.

Raises

• ValueError: If children_field is not provided or is not a string.

Behavior

• Initializes the underlying dictionary with the given *args and **kwargs.
• Sets the children_field attribute for identifying child items in the dictionary.
• Initializes path as an empty list to keep track of the traversal path.
• Sets current to point to the root item (self).
• Sets iter_method to use move_to_next_item by default for iteration.
• Initializes inverted_context as False.

Note

• Keyword arguments will override arguments in *args if overlapping keys are found.

Example

traversal = DictTraversal(data, children_field='children')

---

Method: DictTraversal.__iter__

Description

Initializes the iterator for the DictTraversal object.

Attributes

• path (list): Reset to an empty list.
• current (dict): Reset to point to the root item.

Behavior

• Initializes the iterator for the DictTraversal object.
• Resets the traversal to the root item.
• Returns the DictTraversal object itself to make it an iterator.

Note

• This method resets the traversal to the root item.

Example

# Using __iter__ to reset traversal to root, but next-function is actually required to move to the root!
iter(traversal)  # Represents: {'title': 'root'}

---

Method: DictTraversal.__neg__

Description

Moves the traversal to the previous item.

Behavior

• Can be invoked using the - unary operator.
• Updates the path and current attributes to reflect the new traversal path.

Example

print(last(traversal)['title'])  # Outputs: 'Child 3'
print((-traversal)['title'])  # Outputs: 'Grandgrandchild'

---

Method: DictTraversal.__next__

Description

Advances the iterator to the next item in the traversal.

Attributes

• path (list): Updated to reflect the new traversal path.
• current (dict): Updated to point to the next item in the traversal.

Raises

• StopIteration: If there are no more items to traverse.

Behavior

• Advances the iterator to the next item in the traversal.
• Updates the path and current attributes to reflect the new traversal path.

Note

• This method moves the traversal to the next item relative to the current item.
• Unlike move_to_next_item and move_to_prev_item, which jump over the root and continue from start/end, prev will raise a StopIteration error when it reaches the end of the traversal.

Example

# Using __next__ to move to the next item
try:
    iter(traversal)
    next(traversal)  # Represents: {'title': 'root'}
    next(traversal)  # Represents: {'title': 'Child 1'}
except StopIteration:
    print('No more items to traverse.')

---

Method: DictTraversal.__pos__

Description

Moves the traversal to the next item.

Behavior

• Can be invoked using the + unary operator.
• Updates the path and current attributes to reflect the new traversal path.

Example

print(root(traversal)['title'])  # Outputs: 'root'
print((+traversal)['title'])  # Outputs: 'Child 1'

---

Method: DictTraversal.add_child

Description

Adds a new child item to the current item's children.

Parameters

• *idx: Integer arguments to define the path to the subitems/children, in which to add the item.
• **kwargs: Arbitrary keyword arguments to define the new child item.

Attributes

• current (dict): The current item in the traversal, updated with the new child.

Behavior

• Adds a new child item with the given keyword arguments to the current item's children list.
• Initializes the children list if it doesn't exist.

Example

traversal.add_child(title='Child X')
print(last(traversal))  # Outputs: {'title': 'Child X'}

---

Method: DictTraversal.children

Description

Retrieves the children of the current item.

Parameters

• sibling_only (bool, optional): If True, returns only the siblings of the current item.

Behavior

• If sibling_only is True, returns a list of siblings without their children.
• Otherwise, returns a list of children including their own children.

Example

next(next(root(traversal)))  # Move to Child 2
print(traversal.children())  # Output: [{'title': 'Grandchild 1'}, {'title': 'Grandchild 2', 'sections': [{'title': 'Grandgrandchild'}]}]
print(traversal.children(sibling_only=True))  # Output: [{'title': 'Grandchild 1'}, {'title': 'Grandchild 2'}]

---

Method: DictTraversal.count_children

Description

Counts the number of child items in the current traversal context.

Parameters

• sibling_only (bool): Whether to count only immediate children. Default is False.

Attributes

• current (dict): The current item in the traversal.
• children_field (str): The key used to identify children in the dictionary.

Behavior

• If sibling_only is True, counts only the immediate children of the current item.
• If sibling_only is False, counts all descendants of the current item recursively.
• Utilizes a private recursive function _ for counting when sibling_only is False.

Note

• traversal.count_children() is same as len(traversal)
• traversal.count_children(sibling_only=True) is same as len(traversal[:])

Example

count = traversal.count_children(sibling_only=True)  # Counts only immediate children
print(count)  # Outputs: 3
count = traversal.count_children()  # Counts all descendants
print(count)  # Outputs: 6

---

Method: DictTraversal.find_paths

Description

Locate items by matching their titles to a list of specified field values.

Parameters

• label_field (str): Field name to be used as label of each item. Default is None.
• titles (list or str): Field values to match against item titles. Can be a single string or a list of strings.

Behavior

• Converts titles to a list if it's a single string.
• Initializes an empty list results to store matching items and their paths.
• Defines a recursive function _ to search for items with matching titles.
• Calls _ starting from the current item's subitems, passing the list of remaining titles to match.
• Appends matching items and their paths to results. Items in the result list do not contain childrens.

Example

traversal.find_paths('title', ['Child 2', 'Grandchild 1'])  # Returns: [({'title': 'Grandchild 1'}, [1, 0])

---

Method: DictTraversal.get

Description

Retrieves the value at the specified index key at the current item.

Parameters

• idx (int, slice, tuple, list, str): The index key to retrieve the value from.
• default (any, optional): The default value to return if the index key is not found.

Behavior

• Retrieves the value at the given index key from the object.
• If the index key is not found or the value is None, returns the default value.

Example

value = traversal.get('new_field', default='Not Found')
print(value)  # Output will be the value of the key 'new_field' or 'Not Found'

---

Method: DictTraversal.get_item_by_path

Description

Retrieves the item located at the specified path in the traversal.

Parameters

• path (list): The path to the item in the traversal, represented as a list of integers.

Note

• The method uses the traversal's __getitem__ method to fetch the item.
• Returns None if the path does not exist.

Example

traversal.get_item_by_path([1, 0])  # Returns: {'title': 'Grandchild 1'}

---

Method: DictTraversal.get_last_item

Description

Retrieves the last item in the current traversal tree from the current item perspective.

Parameters

• sibling_only (bool, optional): If True, considers only the siblings.

Example

# Under root
print(traversal.get_last_item())  # Output: {'title': 'Child 3'}
 # Under Child 2
next(next(traversal))
print(traversal.get_last_item())  # Output: {'title': 'Grandgrandchild'}

---

Method: DictTraversal.get_last_item_and_path

Description

Retrieves the last item and its path in the traversal tree from the current item perspective.

Parameters

• sibling_only (bool, optional): If True, considers only the siblings.

Behavior

• If sibling_only is True, returns the last sibling and its path.
• Otherwise, returns the last item in the deepest nested list and its path.

Example

item, path = traversal.get_last_item_and_path()
print(item)  # Output: {'title': 'Child 3'}
print(path)  # Output: [2]

---

Method: DictTraversal.get_last_path

Description

Retrieves the path to the last item in the traversal from the current item perspective.

Parameters

• sibling_only (bool, optional): If True, considers only the siblings.

Example

# Under root
print(traversal.get_last_path())  # Output: [2]
# Under Child 2
next(next(traversal))
print(traversal.get_last_path())  # Output: [1, 1, 0]

---

Method: DictTraversal.get_next_item_and_path

Description

Retrieves the next item and its path without altering the state of the object.

Parameters

• sibling_only (bool, optional): If True, considers only the siblings.

Behavior

• Retrieves the next item and its path relative to the current item.
• If sibling_only is True, returns the next sibling and its path.

Example

root(traversal)
item, path = traversal.get_next_item_and_path()
print(item)  # Output: {'title': 'Child 1'}
print(path)  # Output: [0]

---

Method: DictTraversal.get_parent_item

Description

Retrieves the parent item of the current item in the traversal.

Behavior

• Returns the parent item without its children.
• Returns None if the current item is the root.

Example

root(traversal)
# Move to Grandchild 1
(+++traversal).get_parent_item()  # Returns: {'title': 'Child 2'}

---

Method: DictTraversal.get_parent_item_and_path

Description

Retrieves both the parent item and the path to the parent of the current item in the traversal.

Parameters

• with_children (bool, optional): If True, return the whole traversal tree, not only siblings without children.

Note

• Returns (None, []) if the current item is the root.
• Beware to set self.current to None since it is expected always to be a dictionary - either a root or subitem.

Example

root(traversal)
(+++traversal).get_parent_item_and_path()  # Returns: ({'title': 'Child 2'}, [1])

---

Method: DictTraversal.get_parent_path

Description

Retrieves the path to the parent of the current item in the traversal.

Behavior

• Returns an empty list if the current item is the root.

Example

root(traversal)
# Move to Grandchild 1
(+++traversal).get_parent_path()  # Returns: [1]

---



# Method: `DictTraversal.get_previous_item_and_path`

## Description
Retrieves the previous item and its path without altering the state of the object.

## Parameters
- __sibling_only__ (bool, optional): If True, considers only the siblings.
## Behavior
- Retrieves the previous item and its path relative to the current item.
- If sibling_only is True, returns the previous sibling and its path.

## Example
```python
root(traversal)
item, path = traversal.get_previous_item_and_path()
print(item)  # Output: {'title': 'Child 3'}
print(path)  # Output: [2]

---

Method: DictTraversal.insert_child

Description

Inserts a new child item at a specific index in the current item's children.

Parameters

• idx (int, list, tuple): The index at which to insert the new child. Can be a list or tuple of indices, which points to the deeper hierarchy of children.
• **kwargs: Arbitrary keyword arguments to define the new child item.

Attributes

• current (dict): The current item in the traversal, updated with the new child.

Behavior

• Inserts a new child item with the given keyword arguments at the specified index.
• Initializes the children list if it doesn't exist.

Example

traversal.insert_child(0, title='Child X')
print(first(traversal))  # Outputs: {'title': 'Child X'}

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Method: DictTraversal.inverted

Description

Context manager for backward traversal.

Behavior

• Temporarily sets iter_method to move_to_prev_item.
• Restores the original iter_method after exiting the context.
• Affects the behavior of the following methods:
  • next, prev
  • peek_next, peek_prev
  • for loop iteration
  • first, last
  • root, move_to_next_item, and move_to_prev_item are NOT affected

Note

• This context manager can be nested.
• The state of inverted_context will be restored after exiting each with-block.

Example

# Forward traversal (default behavior)
for item in traversal:
    print(item)

# Backward traversal using the inverted context manager
with traversal.inverted():
    for item in traversal:
        print(item)

---

Method: DictTraversal.max_depth

Description

Returns the maximum depth of the traversal tree of the current item.

Behavior

• Calculates the maximum depth of the traversal tree.
• Depth starts from 0 at the root.

Example

print(traversal.max_depth())  # Output: 3

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Method: DictTraversal.modify

Description

Modifies the current item's attributes.

Parameters

• key (str, optional): The key of the attribute to modify.
• value: The new value for the specified key.
• **kwargs: Arbitrary keyword arguments to update multiple attributes.

Attributes

• current (dict): The current item in the traversal, updated with the new attributes.

Behavior

• Updates the current item's attributes based on the provided key-value pairs.
• If key and value are provided, updates that specific attribute.
• If kwargs are provided, updates multiple attributes.

Example

traversal.modify(title='ROOT')
print(traversal)  # Outputs: {'title': 'ROOT'}

---

Method: DictTraversal.move_to_next_item

Description

Moves the traversal to the next item.

Parameters

• sibling_only (bool, optional): If True, moves only among siblings.

Attributes

• current (dict): Updated to point to the next item in the traversal.
• path (list): Updated to reflect the new traversal path.

Behavior

• Moves the traversal to the next item relative to the current item.
• If sibling_only is True, moves only among siblings.
• Will start over beginning after reaching the end.

Example

root(traversal)
traversal.move_to_next_item()
print(traversal)  # Output: {'title': 'Child 1'}

---

Method: DictTraversal.move_to_prev_item

Description

Retrieves the previous item and its path without altering the state of the object.

Parameters

• sibling_only (bool, optional): If True, considers only the siblings.

Behavior

• Retrieves the previous item and its path relative to the current item.
• If sibling_only is True, returns the previous sibling and its path.
• Will start over the the end after reaching the beginning.

Example

root(traversal)
traversal.move_to_prev_item()
print(traversal)  # Output: {'title': 'Child 3'}

---

Method: DictTraversal.new_root

Description

Context manager for temporarily setting a new root for traversal.

Parameters

• merge (bool): Whether to merge the changes back to the original object. Default is False.

Attributes

• current (dict): Points to the new root item in the traversal if merge is True.
• path (list): Restored to its original state if merge is True.
• inverted_context (bool): Inherits the value from the original object.

Behavior

• If merge is True, creates a new DictTraversal object with the current item as root.
• If merge is False, creates a deep copy of the current DictTraversal object.
• Yields the new DictTraversal object for use within the context.
• If merge is True, updates the root fields and restores the original path after exiting the context.

Example

with traversal.new_root(merge=True) as new_obj:
    # Perform operations on new_obj from the relative traversal path perspective
    # Modifications will affect to the original traversal traversal after with block

with traversal.new_root(merge=False) as new_obj:
    # Perform operations on new_obj from the relative traversal path perspective
    # Modifications will not affect to the original traversal object after with block

---

Method: DictTraversal.peek_next

Description

Peeks at the next item(s) in the traversal without altering the current pointer.

Parameters

• steps (int, optional): Number of steps to peek ahead. Defaults to 1.

Behavior

• Cycles back to the root if the end is reached.
• Temporarily alters the current item and path, restoring them before returning.

Note

• steps must be a positive integer.
• Influenced by the inverted context manager.

Example

print(traversal.peek_next(2))  # Output: {'title': 'Child 2'}

# With inverted context
with traversal.inverted():
    print(traversal.peek_next(2))  # Output: {'title': 'Grandgrandchild'}

---

Method: DictTraversal.peek_prev

Description

Peeks at the previous item(s) in the traversal without altering the current pointer.

Parameters

• steps (int, optional): Number of steps to peek back. Defaults to 1.

Behavior

• Cycles back to the end if the start is reached.
• Temporarily alters the current item and path, restoring them before returning.

Note

• steps must be a positive integer.
• Influenced by the inverted context manager.

Example

print(traversal.peek_prev(2))  # Output: {'title': 'Grandgrandchild'}

# With inverted context
with traversal.inverted():
    traversal.peek_prev(2)  # Output: {'title': 'Child 2'}

---

Method: DictTraversal.pretty_print

Description

Recursively print the tree from the relative current item in a formatted manner.

Parameters

• label_field (str): Field name to be used as label of each item. Default is None.

Behavior

• Prints the string representation of the traversal tree, indented by the specified amount.
• If label_field is not given, repr is used to show the item excluding its children.
• Recursively traverses (inner function _) and prints all children, incrementing the indentation level by 1 for each level.

Example

traversal.pretty_print(label_field='title')  # Output:
# root
#   Child 1
#   Child 2
#      Grandchild 1
#      Grandchild 2
#          Grandchildchild
#   Child 3

---

Method: DictTraversal.replace_child

Description

Replaces an existing child item at a specific index in the current item's children.

Parameters

• idx (int, list, tuple): The index of the child to replace. Can be a list or tuple of indices, which points to the deeper hierarchy of children.
• **kwargs: Arbitrary keyword arguments to define the new child item.

Attributes

• current (dict): The current item in the traversal, updated with the new child.

Behavior

• Replaces the child item at the specified index with a new item defined by the keyword arguments.
• Initializes the children list if it doesn't exist.

Example

traversal.replace_child(0, title='CHILD 1')
print(first(traversal))  # Outputs: {'title': 'CHILD 1'}

---

Method: DictTraversal.search

Description

Search for items whose label match a given query.

Parameters

• query (str, DictSearchQuery or re.Pattern): The search query, either a string, DictSearchQuery or a regular expression pattern.
• label_field (str): Field name to be used as a target of search for each item, if query is str or re.Pattern. Default is None.

Behavior

• Initializes an empty list results to store matching items and their paths.
• Defines a nested function _ to recursively search for items with matching titles.
• Calls _ starting from the current item's subitems.
• Appends matching items and their paths to results.
• Returns results.

Example

result1 = traversal.search('Grandgrandchild', 'title')  # Returns: [({'title': 'Grandgrandchild'}, [1, 1, 0])]
result2 = traversal.search(re.compile(r'Grandchild [0-9]+'), 'title')  # Returns: [({'title': 'Grandchild 1'}, [1, 0]), ({'title': 'Grandchild 2'}, [1, 1])]

---

Method: DictTraversal.set_last_item_as_current

Description

Sets the last item in the traversal as the current item from the current item perspective.

Parameters

• sibling_only (bool, optional): If True, considers only the siblings.

Attributes

• current (dict): Updated to point to the last item in the traversal.
• path (list): Updated to reflect the new traversal path.

Example

traversal.set_last_item_as_current()
print(traversal)  # Output: {'title': 'Child 3'}

---

Method: DictTraversal.set_parent_item_as_current

Description

Sets the parent item in the traversal as the current item from the current item perspective.

Attributes

• current (dict): Updated to point to the parent item in the traversal.
• path (list): Updated to reflect the new traversal path.

Example

+++traversal  # Grandchild 1
traversal.set_parent_item_as_current()
print(traversal)  # Output: {'title': 'Child 2'}

---

Method: DictTraversal.set_path_as_current

Description

Sets the item located at the specified path as the current item in the traversal.

Parameters

• path (list): The path to the item in the traversal, represented as a list of integers.

Note

• Updates both self.current and self.path attributes.
• If the item does not exist at the specified path, self.current and self.path are not updated.

Example

traversal.set_path_as_current([1, 0])  # Sets the current item to the one located at path [1, 0]

---

Method: DictTraversal.visualize

Description

Generates a string representation of the traversal tree.

Parameters

• label_field (str, optional): Field name to be used as the label for each item. Default is None.
• from_root (bool): Whether to start the visualization from the root item. Default is False.

Attributes

• current (dict): The current item in the traversal.
• children_field (str): The key used to identify children in the dictionary.

Behavior

• If from_root is True, starts the visualization from the root item.
• If label_field is provided, uses it as the label for each item.
• Marks the current item with an asterisk (*).

Example

print(next(root(traversal)).visualize('title', from_root=True))  # Output:
# root
# ├── Child 1*
# ├── Child 2
# │   ├── Grandchild 1
# │   └── Grandchild 2
# │       └── Grandgrandchild
# └── Child 3

print(next(next(root(traversal))).visualize('title'))  # Output:
# Child 2*
# ├── Grandchild 1
# └── Grandchild 2
#     └── Grandgrandchild

---

Method: DictSearchQuery.__init__

Description

Initializes a DictSearchQuery object.

Parameters

• query (dict): The query to execute.
• support_wildcards (bool, optional): Flag to enable wildcard support. Defaults to True.
• support_regex (bool, optional): Flag to enable regex support. Defaults to True.
• field_separator (str, optional): The separator for nested keys. Defaults to '.'.
• list_index_indicator (str, optional): The indicator for list indices. Defaults to '#%s'.
• operator_separator (str, optional): The separator between field and operator. Defaults to '$'.

Behavior

• Initializes the query, and sets flags for wildcard and regex support.

Example

query = {'a.b.c': 1}
dsq = DictSearchQuery(query)
data = {'a': {'b': {'c': 1}}, 'd': [ {'e': 2}, {'f': 3, 'g': 4} ]}
result = dsq.execute(data)
print(result)  # Outputs: {'c': 1}

---

Method: DictSearchQuery.execute

Description

Executes the query on the data.

Parameters

• data (dict): The data to query.
• field_separator (str, optional): The separator for nested keys. Defaults to self.field_separator = '.'.
• list_index_indicator (str, optional): The format string for list indices. Defaults to self.list_index_indicator = '#%s'.

Behavior

• Flattens the data using flatten_dict.
• Matches fields based on the query and returns them.

Example

query = {'*': 1}
dsq = DictSearchQuery(query)
data = {'a': {'b': {'c': 1}}, 'd': [ {'e': 2}, {'f': 3, 'g': 4} ]}
dsq.execute(data)  # Results: {'c': 1}

---

Method: DictSearchQuery.reconstruct_item

Description

Reconstructs an item from a nested dictionary based on a flattened query key, using the instance's field separator and list index indicator.

Parameters

• query_key (str): The query key to use for reconstruction.
• item (dict): The nested dictionary.

Note

• Utilizes the standalone reconstruct_item function.
• Uses self.field_separator and self.list_index_indicator for the reconstruction.

Example

data = {'a': {'b': {'c': 1}}, 'd': [ {'e': 2}, {'f': 3, 'g': 4} ]}
DictSearchQuery().reconstruct_item('a.b.c', data)  # Returns: {'c': 1}