Formatters

A Formatter converts features to a different format, such as GeoJSON or Well-Known Text. A Formatter’s output can be customized, then turned into a string or saved to a file.

Properties

These properties customize the Formatter’s output.

Formatter.id

Default: "{T}{id}"

A function or string template used to generate an ID for each feature (only for GeoJSON), or None to omit feature IDs.

By default, the generated ID is a string that starts with N, W or R (for node, way or relation), followed by the feature’s id property (e.g. N54127).
A function must accept a single object (the Feature), and must return a number or string (or an object whose __str__() method returns an ID).
As of Version 0.2.0, only functions are accepted by id. Template support will be added in ~~0.2~~

france("a[leisure=park]").geojson(
    id = lambda f: f.id * 2 + (0 if f.is_way else 1))
    # GeoJSON output with unique IDs, based on the feature's
    # (non-unique) ID, even for ways and odd for relations
    # (since areas can be either)

Formatter.limit

Default: None

If a numeric limit is specified, the Formatter outputs at most n features.

Formatter.linewise

Default: True for geojsonl, otherwise False

For GeoJSON, enables line-by-line output of features (Ignored by other Formatters).

Formatter.mercator

Default: False

If set to True, outputs Mercator-projected coordinates instead of WGS-84 (degrees longitude/latitude).

~~0.2~~

Formatter.precision

Default: 7

The number of digits after the decimal point for coordinate values (A value of 7 equates to a resolution of about 1 cm).

Formatter.pretty

Default: False

If set to True, adds tabs and spacing to make the output easier to read.

Methods

Formatter.save(filename)

Writes the output to a file. If filename has no extension, a default is used.

streets.geojson.save('london-streets')  # Creates london-streets.geojson

GeoJSON

GeoJSON is a widely used format for representing geographic features. For each Feature, the Formatter writes its ID, geometry and properties (its OSM tags).

{
    "type": "FeatureCollection",
    "generator": "geodesk-py/0.1.0",
    "features": [
        {
            "type": "Feature",
            "id": "W6001627",
            "geometry": {
                "type": "LineString",
                "coordinates": [
                    [-117.280372, 32.8393748], [-117.2803909, 32.8396239],
                    [-117.2803957, 32.839872], ... ]
            },
            "properties": {
                "highway": "secondary",
                "name": "Prospect Street",
                ...
            },
            ...
        }
    ]
}

Line-based variant

As an alternative to classic GeoJSON, each Feature is written on a separate line:

{ "type": "Feature", "id": "W6001627", "geometry": { "type": "LineString", ... }}
{ "type": "Feature", "id": "N596184365", "geometry": { "type": "Point", ... }}

Well-Known Text

Well-Know Text (WKT) represents the geometric shapes of features (without IDs or tags).

GEOMETRYCOLLECTION(
    LINESTRING(-117.280372 32.8393748, -117.2803909 32.8396239, ...),
    ...)