Gdal.polygonalization read polygons from shape file obtained

Hi all,
I use gdal library to polygonalize a tif file and using gdal.contour function I can access to polygons geometry with the following command: shape[0].GetGeometryRef().GetPoints()

the code to generate contour is:

dstogr = ogr.GetDriverByName("ESRI Shapefile").CreateDataSource(outputFile)
shape = dstogr.CreateLayer('contour', srs = sr)
fieldContourDefn1 = ogr.FieldDefn("ID", ogr.OFTInteger)
fieldContourDefn2 = ogr.FieldDefn("mdROS", ogr.OFTReal)
gdal.ContourGenerate(srcband, 0, 0 , [1], 0, 0, contourShp, 0, 1)

but with gdal.Polygonize I cannot read points and level of polygons. The code used for tests is:

sourceRaster = gdal.Open(file)
band = sourceRaster.GetRasterBand(1) 
bandArray = band.ReadAsArray()
outShapefile = "POLYGON"
driver = ogr.GetDriverByName("ESRI Shapefile")
outDatasource = driver.CreateDataSource(outShapefile+ ".shp")
outLayer = outDatasource.CreateLayer('polygonized', srs=sr)
newField = ogr.FieldDefn("DN", ogr.OFTInteger)
gdal.Polygonize( band, None, outLayer, -1, [], callback=None )

can someone help me to read shapefile output? if I print outLayer I obtain matrixes of with all elements equal to None

thank you