Can't write decimal data into shape (shp) attribute table with Python

Question

I am trying to create a shapefile with Python GDAL/OGR library. I add to it a real number field, but when I write into it doesn't appear as it should but rounded. I will explain better with the code:

theDriver = driver = ogr.GetDriverByName("ESRI Shapefile")
theShp = driver.CreateDataSource(theFileName)
layer = theShp.CreateLayer(theFileName, geom_type=ogr.wkbPoint)

#create the field
fldN = ogr.FieldDefn('Num', ogr.OFTReal)
layer.CreateField(fldN)

#add a point
pt = ogr.Geometry(ogr.wkbPoint)
pt.AddPoint(lng, lat)
featureDefn = layer.GetLayerDefn()
feature = ogr.Feature(featureDefn)
feature.SetGeometry(pt)

#write the field
feature.SetField('Num', 5.123456)

When I open the shapefile, the field "Num" is set to 5.00000. The extrange thing is that if I change the Driver to "GeoJSON" it works perfect. I tryed to set the precision of the field, but it didn't work.

What happens if you set the field width at 24 (normal default for Esri Shapefile OFTReal) — blord-castillo, Feb 08 '16 at 18:40
what are you using to open the shapefile? With some additions to your posted code I could get the 'num' field to show up as 5.1234500000 opening this in QGIS. The field shows up as length=23, precision=15. — Steven Kay, Feb 08 '16 at 19:23

score 5 · Answer 1 · edited Apr 13 '17 at 12:34

I don't understand your problem

import osgeo.ogr as ogr
import osgeo.osr as osr
driver = ogr.GetDriverByName("ESRI Shapefile")
srs = osr.SpatialReference()
srs.ImportFromEPSG(4326)
# create the data source
data_source = driver.CreateDataSource("test_ogr.shp")
# create the layer
layer = data_source.CreateLayer("test_ogr", srs, ogr.wkbPoint)

# Add the field
layer.CreateField(ogr.FieldDefn("Num", ogr.OFTReal))
feature = ogr.Feature(layer.GetLayerDefn())
feature.SetField("Num", 5.123456)
pt = ogr.Geometry(ogr.wkbPoint)
pt.AddPoint(5,50)
feature.SetGeometry(pt)
layer.CreateFeature(feature)
feature.Destroy()
data_source.Destroy()

Control with Fiona (another GDAL/OGR Python binding)

import fiona
shape = fiona.open("test_ogr.shp")
first = shape.next()
print first
{'geometry': {'type': 'Point', 'coordinates': (5.0, 50.0)}, 'type': 'Feature', 'id': '0', 'properties': OrderedDict([(u'Num', 5.123456)])}
print first['properties']['Num']
5.123456

Control with ogr

from osgeo import ogr
data_source = ogr.Open("test_ogr.shp")
layer = data_source.GetLayer(0)
feature = layer.GetFeature(0)
print feature.ExportToJson()
{"geometry": {"type": "Point", "coordinates": [5.0, 50.0]}, "type": "Feature", "properties": {"Num": 5.123456}, "id": 0}

And it is easier to create a shapefile with Fiona (look at Problem intersecting shapefiles with OGR in Python)

import fiona
from fiona.crs import from_epsg
# schema of the shapefile
schema = {'geometry': 'Point', 'properties': {'Num' : 'float:9.6'}}
crs = from_epsg(4326)
with fiona.open('test_fiona.shp','w',driver='ESRI Shapefile', crs=crs,schema= schema) as output:
    geom = {'type': 'Point', 'coordinates': (5.0, 50.0)}
    prop = {'Num': 5.123456}
    output.write({'geometry':geom, 'properties': prop})

Schema in QGIS

+1 for proposing an alternate library. OGR/GDAL is not well suited for the novice — Frank, Feb 09 '16 at 07:30
thank you @gene to take the time to answer, you are right, that code works. I tried to simplify the code and made a mistake, sorry. My real problem is http://gis.stackexchange.com/questions/180753/problem-using-pyqt4-and-gdal-ogr-together-to-create-a-shapefile. Hope you got the solution too. Thanks again! — Rodrigo E. Principe, Feb 15 '16 at 03:00
FYI, Certain objects contain a Destroy() method, but you should never use it; use something like data_source = None instead — Mike T, Feb 15 '16 at 22:42

Can't write decimal data into shape (shp) attribute table with Python

1 Answers1