graphtage.sequences

Abstract base classes for representing sequences in Graphtage’s intermediate representation.

sequences classes

FixedLengthSequenceEdit

class graphtage.sequences.FixedLengthSequenceEdit(from_node: SequenceNode, to_node: SequenceNode)

Bases: SequenceEdit

An edit for sequences that does not consider interleaving.

__init__(from_node: SequenceNode, to_node: SequenceNode)

Initializes a sequence edit.

Parameters:

from_node – The node being edited.
*args – The remainder of the arguments to be passed to AbstractCompoundEdit.__init__().
**kwargs – The remainder of the keyword arguments to be passed to AbstractCompoundEdit.__init__().

Raises:

ValueError – If from_node is not an instance of SequenceNode.

__iter__() → Iterator[Edit]

Returns an iterator over this edit’s sub-edits.

Returns:: The result of AbstractCompoundEdit.edits()
Return type:: Iterator[Edit]

__lt__(other): Tests whether the bounds of this edit are less than the bounds of other.

_debug_tighten_bounds() → bool: Adds debugging assertions when tightening bounds; for debugging only

bounds() → Range

Returns the bounds of this edit.

This defaults to the bounds provided when this AbstractEdit was constructed. If an upper bound was not provided to the constructor, the upper bound defaults to:

self.from_node.total_size + self.to_node.total_size + 1

Returns:: A range bounding the cost of this edit.
Return type:: Range

edits() → Iterator[Edit]: Returns an iterator over this edit’s sub-edits

from_node: TreeNode

has_non_zero_cost() → bool

Returns whether this edit has a non-zero cost.

This will tighten the edit’s bounds until either its lower bound is greater than zero or its bounds are definitive.

initial_bounds: Range

is_complete() → bool

An edit is complete when no further calls to Edit.tighten_bounds() will change the nature of the edit.

This implementation considers an edit complete if it is valid and its bounds are definitive:

return not self.valid or self.bounds().definitive()

If an edit is able to discern that it has a unique solution even if its final bounds are unknown, it should reimplement this method to define that check.

For example, in the case of a CompoundEdit, this method should only return True if no future calls to Edit.tighten_bounds() will affect the result of CompoundEdit.edits().

Returns:: True if subsequent calls to Edit.tighten_bounds() will only serve to tighten the bounds of this edit and will not affect the semantics of the edit.
Return type:: bool

on_diff(from_node: EditedTreeNode)

A callback for when an edit is assigned to an EditedTreeNode in TreeNode.diff().

This default implementation adds the edit to the node, and recursively calls Edit.on_diff() on all of the sub-edits:

from_node.edit = self
from_node.edit_list.append(self)
for edit in self.edits():
    edit.on_diff(edit.from_node)

Parameters:: from_node – The edited node that was added to the diff

print(formatter: GraphtageFormatter, printer: Printer)

Prints this edit.

This is equivalent to:

formatter.get_formatter(self.sequence)(printer, self.sequence)

property sequence: SequenceNode

Returns the sequence being edited.

This is a convenience function solely to aid in automated type checking. It is equivalent to:

typing.cast(SequenceNode, self.from_node)

tighten_bounds() → bool

Tightens the Edit.bounds() on the cost of this edit, if possible.

Returns:: True if the bounds have been tightened.
Return type:: bool

Note

Implementations of this function should return False if and only if self.bounds().definitive().

property valid: bool: Returns whether this edit is valid

SequenceEdit

class graphtage.sequences.SequenceEdit(from_node: SequenceNode, *args, **kwargs)

Bases: AbstractCompoundEdit, ABC

An edit type for sequence nodes.

__init__(from_node: SequenceNode, *args, **kwargs)

Initializes a sequence edit.

Parameters:

from_node – The node being edited.
*args – The remainder of the arguments to be passed to AbstractCompoundEdit.__init__().
**kwargs – The remainder of the keyword arguments to be passed to AbstractCompoundEdit.__init__().

Raises:

ValueError – If from_node is not an instance of SequenceNode.

__iter__() → Iterator[Edit]

Returns an iterator over this edit’s sub-edits.

Returns:: The result of AbstractCompoundEdit.edits()
Return type:: Iterator[Edit]

__lt__(other): Tests whether the bounds of this edit are less than the bounds of other.

_debug_tighten_bounds() → bool: Adds debugging assertions when tightening bounds; for debugging only

bounds() → Range

Returns the bounds of this edit.

This defaults to the bounds provided when this AbstractEdit was constructed. If an upper bound was not provided to the constructor, the upper bound defaults to:

self.from_node.total_size + self.to_node.total_size + 1

Returns:: A range bounding the cost of this edit.
Return type:: Range

abstractmethod edits() → Iterator[Edit]: Returns an iterator over this edit’s sub-edits

from_node: TreeNode

has_non_zero_cost() → bool

Returns whether this edit has a non-zero cost.

This will tighten the edit’s bounds until either its lower bound is greater than zero or its bounds are definitive.

initial_bounds: Range

is_complete() → bool

An edit is complete when no further calls to Edit.tighten_bounds() will change the nature of the edit.

This implementation considers an edit complete if it is valid and its bounds are definitive:

return not self.valid or self.bounds().definitive()

If an edit is able to discern that it has a unique solution even if its final bounds are unknown, it should reimplement this method to define that check.

For example, in the case of a CompoundEdit, this method should only return True if no future calls to Edit.tighten_bounds() will affect the result of CompoundEdit.edits().

Returns:: True if subsequent calls to Edit.tighten_bounds() will only serve to tighten the bounds of this edit and will not affect the semantics of the edit.
Return type:: bool

on_diff(from_node: EditedTreeNode)

A callback for when an edit is assigned to an EditedTreeNode in TreeNode.diff().

This default implementation adds the edit to the node, and recursively calls Edit.on_diff() on all of the sub-edits:

from_node.edit = self
from_node.edit_list.append(self)
for edit in self.edits():
    edit.on_diff(edit.from_node)

Parameters:: from_node – The edited node that was added to the diff

print(formatter: GraphtageFormatter, printer: Printer)

Prints this edit.

This is equivalent to:

formatter.get_formatter(self.sequence)(printer, self.sequence)

property sequence: SequenceNode

Returns the sequence being edited.

This is a convenience function solely to aid in automated type checking. It is equivalent to:

typing.cast(SequenceNode, self.from_node)

abstractmethod tighten_bounds() → bool

Tightens the Edit.bounds() on the cost of this edit, if possible.

Returns:: True if the bounds have been tightened.
Return type:: bool

Note

Implementations of this function should return False if and only if self.bounds().definitive().

property valid: bool: Returns whether this edit is valid

SequenceFormatter

class graphtage.sequences.SequenceFormatter(*args, **kwargs)

Bases: GraphtageFormatter

A formatter for sequence nodes and edits.

This class will typically be subclassed so that its methods can be overridden to match the style of its parent formatter. For an example, see the implementation of graphtage.json.JSONListFormatter and graphtage.json.JSONDictFormatter.

DEFAULT_INSTANCE: Formatter[T] = <graphtage.GraphtageFormatter object>: A default instance of this formatter, automatically instantiated by the FormatterChecker metaclass.

__init__(start_symbol: str, end_symbol: str, delimiter: str, delimiter_callback: Callable[[Printer], Any] | None = None)

Initializes a sequence formatter.

Parameters:

start_symbol – The symbol to print at the start of the sequence.
end_symbol – The symbol to print at the end of the sequence.
delimiter – A delimiter to print between items.
delimiter_callback –
A callback for when a delimiter is to be printed. If omitted, this defaults to:
```
lambda p: p.write(delimiter)
```

static __new__(cls, *args, **kwargs) → Formatter[T]

Instantiates a new formatter.

This automatically instantiates and populates Formatter.sub_formatters and sets their parent to this new formatter.

edit_print(printer: Printer, edit: Edit)

Called when the edit for an item is to be printed.

If the SequenceNode being printed either is not edited or has no edits, then the edit passed to this function will be a Match(child, child, 0).

This implementation simply delegates the print to the Formatting Protocol:

self.print(printer, edit)

get_formatter(item: T) → Callable[[Printer, T], Any] | None

Looks up a formatter for the given item using this formatter as a base.

Equivalent to:

get_formatter(item.__class__, base_formatter=self)

is_partial: bool = True: This is a partial formatter; it will not be automatically used in the Formatting Protocol.

item_newline(printer: Printer, is_first: bool = False, is_last: bool = False)

Called before each node is printed.

This is also called one extra time after the last node, if there is at least one node printed.

The default implementation is simply:

printer.newline()

items_indent(printer: Printer) → Printer

Returns a Printer context with an indentation.

This is called as:

with self.items_indent(printer) as p:

immediately after the self.start_symbol is printed, but before any of the items have been printed.

This default implementation is equivalent to:

return printer.indent()

parent: Formatter[T] | None = None

The parent formatter for this formatter instance.

This is automatically populated by Formatter.__new__() and should never be manually modified.

print(printer: Printer, node_or_edit: TreeNode | Edit, with_edits: bool = True)

Prints the given node or edit.

Parameters:

printer – The printer to which to write.
node_or_edit – The node or edit to print.
with_edits – If :keyword:True, print any edits associated with the node.

Note

The protocol for determining how a node or edit should be printed is very complex due to its extensibility. See the Printing Protocol for a detailed description.

print_SequenceNode(printer: Printer, node: SequenceNode)

Formats a sequence node.

The protocol for this function is as follows:

Print self.start_symbol
With the printer returned by self.items_indent:
- For each edit in the sequence (or just a sequence of graphtage.Match for each child, if the node is not edited):
  
  Call self.item_newline(printer, is_first=index == 0)
  
  Call self.edit_print(printer, edit)
If at least one edit was printed, then call self.item_newline(printer, is_last=True)
Print self.start_symbol

property root: Formatter[T]: Returns the root formatter.

sub_format_types: Sequence[Type[Formatter[T]]] = (): A list of formatter types that should be used as sub-formatters in the Formatting Protocol.

sub_formatters: List[Formatter[T]] = []

The list of instantiated formatters corresponding to Formatter.sub_format_types.

This list is automatically populated by Formatter.__new__() and should never be manually modified.

SequenceNode

class graphtage.sequences.SequenceNode(children: T)

Bases: ContainerNode, Generic[T], ABC

A node representing a sequence, like a list, set, or dict.

__init__(children: T)

Initializes a sequence node.

Parameters:: children – A sequence of TreeNodes. This is assigned to the protected member SequenceNode._children.

__iter__() → Iterator[TreeNode]

Iterates over this sequence’s child nodes.

This is equivalent to:

return iter(self._children)

__len__() → int

The number of children of this sequence.

This is equivalent to:

return len(self._children)

add_edit_modifier(modifier: Callable[[TreeNode, TreeNode], Edit | None])

all_children_are_leaves() → bool

Tests whether all of the children of this container are leaves.

Equivalent to:

all(c.is_leaf for c in self)

Returns:: True if all children are leaves.
Return type:: bool

calculate_total_size()

Calculates the total size of this sequence.

This is equivalent to:

return sum(c.total_size for c in self)

children() → Sequence[TreeNode]

The children of this node.

Equivalent to:

list(self)

abstract property container_type: Type[T]

Returns the container type used to store SequenceNode._children.

This is used for performing a deep copy of this node in the SequenceNode.editable_dict() function.

copy() → T: Creates a deep copy of this node

copy_from(children: Iterable[TreeNode]) → T: Constructs a new instance of this tree node from a list of its children

dfs() → Iterator[TreeNode]

Performs a depth-first traversal over all of this node’s descendants.

self is always included and yielded first.

This implementation is equivalent to:

stack = [self]
while stack:
    node = stack.pop()
    yield node
    stack.extend(reversed(node.children()))

diff(node: TreeNode) → EditedTreeNode | T

Performs a diff against the provided node.

Parameters:: node – The node against which to perform the diff.
Returns:: An edited version of this node with all edits being completed.
Return type:: Union[EditedTreeNode, T]

editable_dict() → Dict[str, Any]

Copies self.__dict__, calling TreeNode.editable_dict() on all children.

This is equivalent to:

ret = dict(self.__dict__)
ret['_children'] = self.container_type(n.make_edited() for n in self)
return ret

This is used by SequenceNode.make_edited().

property edited: bool

Returns whether this node has been edited.

The default implementation returns False, whereas EditedTreeNode.edited() returns True.

abstractmethod edits(node: TreeNode) → Edit

Calculates the best edit to transform this node into the provided node.

Parameters:: node – The node to which to transform.
Returns:: The best possible edit.
Return type:: Edit

get_all_edit_contexts(node: TreeNode) → Iterator[Tuple[Tuple[TreeNode, ...], Edit]]

Returns an iterator over all edit contexts that will transform this node into the provided node.

Parameters:: node – The node to which to transform this one.
Returns:: An iterator over pairs of paths from node to the edited node, as well as its edit. Note that this iterator will automatically explode any CompoundEdit in the sequence.
Return type:: Iterator[Tuple[Tuple[“TreeNode”, …], Edit]

get_all_edits(node: TreeNode) → Iterator[Edit]

Returns an iterator over all edits that will transform this node into the provided node.

Parameters:: node – The node to which to transform this one.
Returns:: An iterator over edits. Note that this iterator will automatically explode any CompoundEdit in the sequence.
Return type:: Iterator[Edit]

property is_leaf: bool

Container nodes are never leaves, even if they have no children.

Returns:: False
Return type:: bool

make_edited() → EditedTreeNode | T

Returns a new, copied instance of this node that is also an instance of EditedTreeNode.

This is equivalent to:

return self.__class__.edited_type()(self)

Returns:: A copied version of this node that is also an instance of EditedTreeNode and thereby mutable.
Return type:: Union[EditedTreeNode, T]

property parent: TreeNode | None

The parent node of this node, or None if it has no parent.

The setter for this property should only be called by the parent node setting itself as the parent of its child.

ContainerNode subclasses automatically set this property for all of their children. However, if you define a subclass of TreeNode does not extend off of ContainerNode and for which len(self.children()) > 0, then each child’s parent must be set.

print(printer: Printer)

Prints a sequence node.

By default, sequence nodes are printed like lists:

SequenceFormatter('[', ']', ',').print(printer, self)

print_parent_context(printer: Printer, for_child: TreeNode)

Prints the context for the given child node.

For example, if this node represents a list and the child is the element at index 3, then “[3]” might be printed.

The child is expected to be one of this node’s children, but this is not validated.

The default implementation prints nothing.

abstractmethod to_obj()

Returns a pure Python representation of this node.

For example, a node representing a list, like graphtage.ListNode, should return a Python list. A node representing a mapping, like graphtage.MappingNode, should return a Python dict. Container nodes should recursively call TreeNode.to_obj() on all of their children.

This is used solely for the providing objects to operate on in the commandline expressions evaluation, for options like –match-if and –match-unless.

property total_size: int

The size of this node.

This is an arbitrary, immutable value that is used to calculate the bounded costs of edits on this node.

The first time this property is called, its value will be set and memoized by calling TreeNode.calculate_total_size().

Returns:: An arbitrary integer representing the size of this node.
Return type:: int