PolyLine

# Coordinates are 15 points on the great circle from Boston to San Francisco.
coordinates = [
    [42.3581, -71.0636],
    [42.82995815, -74.78991444],
    [43.17929819, -78.56603306],
    [43.40320216, -82.37774519],
    [43.49975489, -86.20965845],
    [43.46811941, -90.04569087],
    [43.30857071, -93.86961818],
    [43.02248456, -97.66563267],
    [42.61228259, -101.41886832],
    [42.08133868, -105.11585198],
    [41.4338549, -108.74485069],
    [40.67471747, -112.29609954],
    [39.8093434, -115.76190821],
    [38.84352776, -119.13665678],
    [37.7833, -122.4167],
]

# Create the map and add the line
m = folium.Map(location=[41.9, -97.3], zoom_start=4)

folium.PolyLine(
    locations=coordinates,
    color="#FF0000",
    weight=5,
    tooltip="From Boston to San Francisco",
).add_to(m)

m

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Smoothing

PolyLine objects in Leaflet are smoothed by default. This removes points from the line, putting less load on the browser when drawing. The level of smoothing can be set with the smooth_factor argument.

m = folium.Map(location=[41.9, -97.3], zoom_start=4)

folium.PolyLine(
    smooth_factor=50,
    locations=coordinates,
    color="grey",
    tooltip="Too much smoothing?",
    weight=5,
).add_to(m)

m

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Crossing the date line

Take notice how lines behave when they cross the date line.

lon = lat = 0
zoom_start = 1

m = folium.Map(location=[lat, lon], zoom_start=zoom_start)

kw = {"opacity": 1.0, "weight": 6}
folium.PolyLine(
    locations=[(2, 179), (2, -179)],
    tooltip="Wrong",
    color="red",
    line_cap="round",
    **kw,
).add_to(m)

folium.PolyLine(
    locations=[(-2, 179), (-2, 181)],
    tooltip="Correct",
    line_cap="butt",
    color="blue",
    **kw,
).add_to(m)

folium.PolyLine(
    locations=[(-6, -179), (-6, 179)],
    line_cap="square",
    color="green",
    tooltip="Correct",
    **kw,
).add_to(m)

folium.PolyLine(
    locations=[(12, -179), (12, 190)],
    color="orange",
    tooltip="Artifact?",
    **kw,
).add_to(m)

m

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Multi-PolyLine

You can create multiple polylines by passing multiple sets of coordinates to a single PolyLine object.

lat = +38.89399
lon = -77.03659
zoom_start = 17

m = folium.Map(location=[lat, lon], zoom_start=zoom_start)

kw = {"color": "red", "fill": True, "radius": 20}

folium.CircleMarker([38.89415, -77.03738], **kw).add_to(m)
folium.CircleMarker([38.89415, -77.03578], **kw).add_to(m)


locations = [
    [
        (38.893596444352134, -77.03814983367920),
        (38.893379333722040, -77.03792452812195),
    ],
    [
        (38.893379333722040, -77.03792452812195),
        (38.893162222428310, -77.03761339187622),
    ],
    [
        (38.893162222428310, -77.03761339187622),
        (38.893028615148424, -77.03731298446655),
    ],
    [
        (38.893028615148424, -77.03731298446655),
        (38.892920059048464, -77.03691601753235),
    ],
    [
        (38.892920059048464, -77.03691601753235),
        (38.892903358095296, -77.03637957572937),
    ],
    [
        (38.892903358095296, -77.03637957572937),
        (38.893011914220770, -77.03592896461487),
    ],
    [
        (38.893011914220770, -77.03592896461487),
        (38.893162222428310, -77.03549981117249),
    ],
    [
        (38.893162222428310, -77.03549981117249),
        (38.893404384982480, -77.03514575958252),
    ],
    [
        (38.893404384982480, -77.03514575958252),
        (38.893596444352134, -77.03496336936950),
    ],
]

folium.PolyLine(
    locations=locations,
    color="orange",
    weight=8,
    opacity=1,
    smooth_factor=0,
).add_to(m)

m

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