---
title: "LayerMapping verktyg för dataimport"
version: 6.0
locale: sv
source: https://docs.djangoproject.com/sv/6.0/ref/contrib/gis/layermapping/
canonical: https://djangodocs.dev/sv/6.0/ref/contrib/gis/layermapping/
---
# `LayerMapping` verktyg för dataimport

Klassen [`LayerMapping`](#django.contrib.gis.utils.LayerMapping) ger ett sätt att mappa innehållet i vektorbaserade rumsliga datafiler (t.ex. shapefiler) till GeoDjango-modeller.

Detta verktyg växte fram ur författarens personliga behov av att eliminera kodupprepningen som gick ut på att dra ut geometrier och fält från ett vektorlager, konvertera till ett annat koordinatsystem (t.ex. WGS84) och sedan infoga i en GeoDjango-modell.

> **Note**
>
> Användning av [`LayerMapping`](#django.contrib.gis.utils.LayerMapping) kräver GDAL.

> **Warning**
>
> GIS data sources, like shapefiles, may be very large. If you find that
> [`LayerMapping`](#django.contrib.gis.utils.LayerMapping) is using too much memory, set [`DEBUG`](/sv/6.0/ref/settings/#std-setting-DEBUG) to
> `False` in your settings. When [`DEBUG`](/sv/6.0/ref/settings/#std-setting-DEBUG) is set to `True`,
> Django [automatically logs](/sv/6.0/faq/models/#faq-see-raw-sql-queries) *every* SQL
> query – and when SQL statements contain geometries, this may consume more
> memory than is typical.

## Exempel

1. Du behöver en GDAL-stödd datakälla, t.ex. en shapefil (här använder vi en enkel polygon-shapefil, `test_poly.shp`, med tre funktioner):

```pycon
>>> from django.contrib.gis.gdal import DataSource
>>> ds = DataSource("test_poly.shp")
>>> layer = ds[0]
>>> print(layer.fields)  # Exploring the fields in the layer, we only want the 'str' field.
['float', 'int', 'str']
>>> print(len(layer))  # getting the number of features in the layer (should be 3)
3
>>> print(layer.geom_type)  # Should be 'Polygon'
Polygon
>>> print(layer.srs)  # WGS84 in WKT
GEOGCS["GCS_WGS_1984",
    DATUM["WGS_1984",
        SPHEROID["WGS_1984",6378137,298.257223563]],
    PRIMEM["Greenwich",0],
    UNIT["Degree",0.017453292519943295]]
```

1. Nu definierar vi vår motsvarande Django-modell (se till att använda [`migrate`](/sv/6.0/ref/django-admin/#django-admin-migrate)):

   ```
   from django.contrib.gis.db import models

   class TestGeo(models.Model):
       name = models.CharField(max_length=25)  # corresponds to the 'str' field
       poly = models.PolygonField(srid=4269)  # we want our model in a different SRID

       def __str__(self):
           return "Name: %s" % self.name
   ```
2. Använd [`LayerMapping`](#django.contrib.gis.utils.LayerMapping) för att extrahera alla funktioner och placera dem i databasen:

```pycon
>>> from django.contrib.gis.utils import LayerMapping
>>> from geoapp.models import TestGeo
>>> mapping = {
...     "name": "str",  # The 'name' model field maps to the 'str' layer field.
...     "poly": "POLYGON",  # For geometry fields use OGC name.
... }  # The mapping is a dictionary
>>> lm = LayerMapping(TestGeo, "test_poly.shp", mapping)
>>> lm.save(verbose=True)  # Save the layermap, imports the data.
Saved: Name: 1
Saved: Name: 2
Saved: Name: 3
```

Here, [`LayerMapping`](#django.contrib.gis.utils.LayerMapping) transformed the three geometries from the shapefile
in their original spatial reference system (WGS84) to the spatial reference
system of the GeoDjango model (NAD83). If no spatial reference system is
defined for the layer, use the `source_srs` keyword with a
[`SpatialReference`](/sv/6.0/ref/contrib/gis/gdal/#django.contrib.gis.gdal.SpatialReference) object to specify one.

## aPI `LayerMapping` API

#### `class LayerMapping(model, data_source, mapping, layer=0, source_srs=None, encoding=None, transaction_mode='commit_on_success', transform=True, unique=True, using='default')`

Följande är de argument och nyckelord som kan användas vid instansiering av `LayerMapping` objekt.

| Argument | Beskrivning |
| --- | --- |
| `modell` | Den geografiska modellen, *inte* en instans. |
| `datakälla` | The path to the OGR-supported data source file<br>(e.g., a shapefile). Also accepts<br>[`django.contrib.gis.gdal.DataSource`](/sv/6.0/ref/contrib/gis/gdal/#django.contrib.gis.gdal.DataSource) instances. |
| `mappning` | En ordbok: nycklarna är strängar som motsvarar modellfältet och värdena motsvarar strängfältsnamn för OGR-objektet, eller om modellfältet är geografiskt bör det motsvara OGR:s geometrityp, t.ex. `'POINT'`, `'LINESTRING'`, `'POLYGON'`. |

| Argument för nyckelord |  |
| --- | --- |
| `lager` | Indexet för det lager som ska användas från datakällan (standardvärde 0) |
| `källa_srs` | Use this to specify the source SRS manually (for<br>example, some shapefiles don’t come with a `'.prj'`<br>file). An integer SRID, WKT or PROJ strings, and<br>[`django.contrib.gis.gdal.SpatialReference`](/sv/6.0/ref/contrib/gis/gdal/#django.contrib.gis.gdal.SpatialReference)<br>objects are accepted. |
| `kodning` | Specifies the character set encoding of the strings<br>in the OGR data source. For example, `'latin-1'`,<br>`'utf-8'`, and `'cp437'` are all valid encoding<br>parameters. |
| `transaktionsläge` | Kan vara `'commit_on_success` (standard) eller `'autocommit`. |
| `transform` | Setting this to False will disable coordinate<br>transformations. In other words, geometries will<br>be inserted into the database unmodified from their<br>original state in the data source. |
| `unique` | Setting this to the name, or a tuple of names,<br>from the given  model will create models unique<br>only to the given name(s). Geometries from<br>each feature will be added into the collection<br>associated with the unique model. Forces<br>the transaction mode to be `'autocommit'`. |
| `använder` | Anger den databas som ska användas vid import av rumsliga data. Standard är `'default'`. |

### `save()` Nyckelord Argument

#### `LayerMapping.save(verbose=False, fid_range=False, step=False, progress=False, silent=False, stream=sys.stdout, strict=False)`

The `save()` method also accepts keywords. These keywords are
used for controlling output logging, error handling, and for importing
specific feature ranges.

| Spara sökordsargument | Beskrivning |
| --- | --- |
| `fid_range` | May be set with a slice or tuple of<br>(begin, end) feature ID’s to map from<br>the data source. In other words, this<br>keyword enables the user to selectively<br>import a subset range of features in the<br>geographic data source. |
| `framsteg` | When this keyword is set, status information<br>will be printed giving the number of features<br>processed and successfully saved. By default,<br>progress information will be printed every 1000<br>features processed, however, this default may<br>be overridden by setting this keyword with an<br>integer for the desired interval. |
| `silent` | Som standard skrivs icke-fatala felmeddelanden ut till `sys.stdout`, men detta nyckelord kan anges för att inaktivera dessa meddelanden. |
| `steg` | Om det anges med ett heltal kommer transaktioner att ske vid varje stegintervall. Om t.ex. `step=1000`, kommer en transaktion att ske efter den 1 000:e funktionen, den 2 000:e funktionen osv. |
| `ström` | Status information will be written to this file<br>handle. Defaults to using `sys.stdout`, but<br>any object with a `write` method is supported. |
| `strikt` | Execution of the model mapping will cease upon<br>the first error encountered. The default value<br>(`False`)<br>behavior is to attempt to continue. |
| `verbose` | Om den är inställd kommer information att skrivas ut efter varje modellsparning som utförs i databasen. |

## Felsökning

### Minnet tar slut

As noted in the warning at the top of this section, Django stores all SQL
queries when `DEBUG=True`. Set `DEBUG=False` in your settings, and this
should stop excessive memory use when running `LayerMapping` scripts.

### MySQL: `max_allowed_packet` fel

Om du stöter på följande fel när du använder `LayerMapping` och MySQL:

```pytb
OperationalError: (1153, "Got a packet bigger than 'max_allowed_packet' bytes")
```

Then the solution is to increase the value of the `max_allowed_packet`
setting in your MySQL configuration. For example, the default value may
be something low like one megabyte – the setting may be modified in MySQL’s
configuration file (`my.cnf`) in the `[mysqld]` section:

```ini
max_allowed_packet = 10M
```