[
    {
        "role": "user",
        "content": "in%20osmnx%2C%20the%20edges%20do%20not%20include%20a%20length%20attribute%20by%20default%20it%20seems.%20any%20way%20to%20fix%3F"
    },
    {
        "role": "assistant",
        "content": "In OSMnx (v2.0+), edges *do* have a `length` attribute by default *if* you're using its built\u2010in graph creation functions (e.g. `graph_from_place`, `graph_from_bbox`, etc.). The `length` attribute represents the edge length in **meters**. ([osmnx.readthedocs.io](https://osmnx.readthedocs.io/en/stable/getting-started.html?utm_source=openai))\n\nIf you're finding that your edges **don\u2019t** include a `length` attribute, this is often because:\n\n1. Edges were added *manually* (after graph construction), so they lack the automatically populated attributes.  \n2. You created or modified the graph (or edges) in a way that bypassed the usual OSMnx processes that add those attributes.  \n3. You loaded or saved the graph in a format that dropped `data` attributes (e.g. certain exports/imports).  \n\nTo fix that, here are a few methods:\n\n---\n\n## \u2705 Solutions to restore/add the `length` attribute\n\n### 1. Use `add_edge_lengths(G)`\n\nOSMnx includes a function in `osmnx.distance` called `add_edge_lengths(G)` which computes and adds `length` in meters for every edge in a graph. Use this when edges are missing the `length` attribute. ([osmnx.readthedocs.io](https://osmnx.readthedocs.io/_/downloads/en/stable/pdf/?utm_source=openai))\n\n```python\nimport osmnx as ox\n\nG = ox.graph_from_place(\"City, Country\", network_type=\"drive\")\n\n# Suppose edges are missing 'length'\nG = ox.distance.add_edge_lengths(G)\n```\n\n- Note: OSMnx automatically runs `add_edge_lengths()` when you do the initial graph construction (before simplification) in most graph-from-XXX functions. ([osmnx.readthedocs.io](https://osmnx.readthedocs.io/_/downloads/en/stable/pdf/?utm_source=openai))  \n- After simplification (which merges and simplifies geometry), edge geometries may be curved or non-straight. If you run `add_edge_lengths()` after simplification, it will compute great-circle (straight-line) node-to-node distances, which may understate actual curvy geometry. ([osmnx.readthedocs.io](https://osmnx.readthedocs.io/_/downloads/en/stable/pdf/?utm_source=openai))\n\n### 2. When you plot routes and face `KeyError: 'length'`\n\nSome OSMnx plotting/routing functions expect `length` to be present. For example, `plot_graph_route` will error out if edges lack `length`. In that case, as others on StackOverflow have pointed out, you can either:\n\n- Add `length` via `add_edge_lengths(G)` before routing and plotting; or  \n- Add it manually to each edge using node position/geometry if you have access to node coordinates. ([stackoverflow.com](https://stackoverflow.com/questions/72642476/how-can-i-solve-the-problem-occur-in-osmnx-plot-graph-route-keyerror-length?utm_source=openai))\n\n### 3. Inspect the edge attribute keys\n\nSometimes your graph already *has* a length attribute under a different schema (perhaps named differently), or the attribute is missing because of how you converted GeoDataFrames or loaded the graph. To inspect:\n\n```python\nedges = ox.graph_to_gdfs(G, nodes=False, edges=True)\nprint(edges.columns)  # see if 'length' is among them\n```\n\nIf it\u2019s missing, go with method (1) or (2).\n\n---\n\n## \u26a0\ufe0f Best practices and caveats\n\n- Work with **unprojected graphs** (`crs=4326`, latitude/longitude) when using `add_edge_lengths()`, so that the great-circle distance between the nodes is correctly computed in meters. ([osmnx.readthedocs.io](https://osmnx.readthedocs.io/_/downloads/en/stable/pdf/?utm_source=openai))  \n- Avoid running `add_edge_lengths()` after simplifying the geometry if you want realistic edge lengths (because simplification merges straight segments into curved geometry, but lengths are still computed straight). ([osmnx.readthedocs.io](https://osmnx.readthedocs.io/_/downloads/en/stable/pdf/?utm_source=openai))  \n- Always verify that edges have the length attribute before using functions that expect it (routing, plotting, stats). If needed, reuse `add_edge_lengths()` on your modified graph object.\n\n---\n\nIf you like, I can walk you through *exactly* when your graph is missing `length` (you can show me the code you used), and help you plug it in so everything downstream works."
    }
]