Flask-Leaflet

Flask-Leaflet provides a simple interface to use LeafletJS API with Flask.

🚧 This package is under heavy development..

Installation

Install the extension with pip:

pip install flask-leaflet

Install with uv:

uv add flask-leaflet

Configuration

This are some of the settings available

Usage

Once installed Flask-Leaflet is easy to use. Let's walk through setting up a basic application. Also please note that this is a very basic guide: we will be taking shortcuts here that you should never take in a real application.

To begin we'll set up a Flask app:

from flask import Flask
from flask_leaflet import Leaflet

app = Flask(__name__)

leaflet = Leaflet()
leaflet.init_app(app)

Load resources

Once the extension is set up, this will make available the leaflet object into the templates context so you could load the javascript and css package easily, like this.

<head>
  {{ leaflet.load() }}
</head>

Constructing a Map

Once the resources are loaded into the head, then we need to constructo our first map.

from flask import render_template
from flask_leaflet import Map

@app.get('/my-map')
def my_map():
    # You got every option available in the original LeafletJS
    # Using snake_case for the options.
    my_map = Map('my-map', center=[-41.139416, -73.025431], zoom=16)
    return render('my_map.html', my_map=my_map)

Rendering the map

Now that we have a Map instance we can render it in a template. IMPORTANT: The map container Must have a Height given the special class_ argument. Also you got access to nonce_ in case you need to add a nonce token to the script tag. in the next example we use tailwindcss class for a 200px height

<body>
  <!-- You can add custom options at this instance that will overwrite any defaults coming from the view. Note that using class_='h-200px' we stablish a minimum height otherwise the map wouldnt be visible. -->
  {{ leaflet.render_map(my_map, class_='h-[200px]', zoom=10) }}
</body>

What about RasterLayers

If you need to use a RasterTile style for every map you could stablish in your configuration the url_template and options for the default raster. Doing this will automatically be seted up for every map rendered.

You can also do it programatically in python as follows.

# ...
my_map = Map('my-map', center=[-41.139416, -73.025431], zoom=16)
my_map.new_tile_layer(r"https://server.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer/tile/{z}/{y}/{x}", max_zoom=15, min_zoom=10)

or

from flask_leaflet.layers.raster import TileLayer
# ...
my_map = Map('my-map', center=[-41.139416, -73.025431], zoom=16)
tile_layer = TileLayer(r"https://server.arcgisonline.com/ArcGIS/rest/services/World_Imagery/MapServer/tile/{z}/{y}/{x}", max_zoom=15, min_zoom=10)
my_map.layers.append(tile_layer)

What about Markers and Polys

If you want to add a marker to your map, you could do it like so.

# ...
my_map = Map('my-map', center=[-41.139416, -73.025431], zoom=16)
my_marker = my_map.new_marker([-41.139416, -73.025431], opacity=0.8)

# if you want to add a tooltip to your marker
my_marker.new_tooltip('My Marker Tooltip')

# To add a popup associated with the marker
my_marker.new_popup('<b>This is the popup content</b>')

# Adding Polys
circle = my_map.new_circle([-41.139416, -73.025431], radius=15)
# You can add popups and tooltips as well
circle.new_tooltip('This is a circle tooltip')

rectangle = my_map.new_rectangle([[-41.139416, -73.025431],[-41.139446, -73.025451]])
rectangle.new_popup('This is a rectangle popup')

I will be adding more functionallity in the future to extend the capabilities and customization options. Help is always welcomed.