graph_png.py — langchain Source File

Source Code

"""Helper class to draw a state graph into a PNG file."""

from itertools import groupby
from typing import Any, cast

from langchain_core.runnables.graph import Graph, LabelsDict

try:
    import pygraphviz as pgv  # type: ignore[import-not-found]

    _HAS_PYGRAPHVIZ = True
except ImportError:
    _HAS_PYGRAPHVIZ = False


class PngDrawer:
    """Helper class to draw a state graph into a PNG file.

    It requires `graphviz` and `pygraphviz` to be installed.

    Example:
        ```python
        drawer = PngDrawer()
        drawer.draw(state_graph, "graph.png")
        ```
    """

    def __init__(
        self, fontname: str | None = None, labels: LabelsDict | None = None
    ) -> None:
        """Initializes the PNG drawer.

        Args:
            fontname: The font to use for the labels. Defaults to "arial".
            labels: A dictionary of label overrides. The dictionary
                should have the following format:
                {
                    "nodes": {
                        "node1": "CustomLabel1",
                        "node2": "CustomLabel2",
                        "__end__": "End Node"
                    },
                    "edges": {
                        "continue": "ContinueLabel",
                        "end": "EndLabel"
                    }
                }
                The keys are the original labels, and the values are the new labels.

        """
        self.fontname = fontname or "arial"
        self.labels = labels or LabelsDict(nodes={}, edges={})

    def get_node_label(self, label: str) -> str:
        """Returns the label to use for a node.

        Args:
            label: The original label.

        Returns:
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