blender modified asc reader importer handles garbage values (-9999 -> 100 )

modified_asc_reader_handles_garbage.py

import bpy  
import time
import csv

A = time.time()


# dfile = r"C:\Users\dealga\Desktop\Archive\SU8606_DSM_1M.asc"
dfile = r"C:\Users\zeffi\Downloads\rubber\LIDAR-DTM-2M-NZ24\nz2146_DTM_2m.asc"

getval = lambda i: int(next(i).split()[1])

with open(dfile) as ofile:
    ncols = getval(ofile)
    nrows = getval(ofile)
    xllcorner = getval(ofile)
    yllcorner = getval(ofile)
    cellsize = getval(ofile)
    NODATA_value = getval(ofile)
    
    print(ncols, nrows, xllcorner, yllcorner, cellsize, NODATA_value)

    # this will read the rest
    verts = []
    add_vert = verts.append
    # asc_reader = csv.reader(ofile, delimiter=' ')
    
    ni = nrows #? +1 -1
    nj = ncols #? +1 -1
    # ni = 500
    # nj = 500
        
    for i, row in enumerate(ofile):
        row_data = row.strip().split(' ')
        row_data = [float(d) for d in row_data]
        if i >= ni:
            break
        for j in range(int(ncols)):
            if j >= nj:
                break

            # uk survey has a lot of garbage data in some .asc files
            datum = 100 if (row_data[j] == -9999) else row_data[j]
                
            z = float(datum) / 60
            x = j * 0.01   #   cell x width
            y = i * 0.01   #   cell y width
            add_vert((x,y,z))
            
    print('done')
    print('last vertex:', verts[-1])

B = time.time()

total_time = B-A
print('total_time:', total_time)

faces = []
add_face = faces.append

# generate_edges, i = verts y, j = verts x
total_range = ((ni-1) * (nj))
indices = []
for i in range(total_range):
    if not ((i+1) % nj == 0):
        add_face([i, i+nj, i+nj+1, i+1])

# do your own error handling
mesh_data = bpy.data.meshes.new("LIDAR_mesh_data3")  
mesh_data.from_pydata(verts, [], faces)  
mesh_data.update()
  
LIDAR_object = bpy.data.objects.new("LIDAR_Object3", mesh_data)  
  
scene = bpy.context.scene    
scene.objects.link(LIDAR_object)    
LIDAR_object.select = True        

modified_original_with_skipping_whitespace.py

import bpy  
import time
import csv

A = time.time()


# dfile = r"C:\Users\dealga\Desktop\Archive\SU8606_DSM_1M.asc"
dfile = r"C:\Users\zeffi\Downloads\rubber\LIDAR-DTM-2M-NZ24\nz2141_DTM_2m.asc"

getval = lambda i: int(next(i).split()[1])

with open(dfile) as ofile:
    ncols = getval(ofile)
    nrows = getval(ofile)
    xllcorner = getval(ofile)
    yllcorner = getval(ofile)
    cellsize = getval(ofile)
    NODATA_value = getval(ofile)
    
    print(ncols, nrows, xllcorner, yllcorner, cellsize, NODATA_value)

    # this will read the rest
    verts = []
    add_vert = verts.append
    asc_reader = csv.reader(ofile, skipinitialspace=True, delimiter=' ')
    
    ni = nrows #? +1 -1
    nj = ncols #? +1 -1
        
    for i, row in enumerate(asc_reader):
        if i >= ni:
            break
        for j in range(int(ncols)):
            if j >= nj:
                break
            datum = 100 if (row[j] == str(NODATA_value)) else row[j]
            z = float(datum) / 60
            x = j * 0.01   #   cell x width
            y = i * 0.01   #   cell y width
            add_vert((x,y,z))
            
    print('done')
    print('last vertex:', verts[-1])

B = time.time()

total_time = B-A
print('total_time:', total_time)

faces = []
add_face = faces.append

# generate_edges, i = verts y, j = verts x
total_range = ((ni-1) * (nj))
indices = []
for i in range(total_range):
    if not ((i+1) % nj == 0):
        add_face([i, i+nj, i+nj+1, i+1])

# do your own error handling
mesh_data = bpy.data.meshes.new("LIDAR_mesh_data3")  
mesh_data.from_pydata(verts, [], faces)  
mesh_data.update()
  
LIDAR_object = bpy.data.objects.new("LIDAR_Object3", mesh_data)  
  
scene = bpy.context.scene    
scene.objects.link(LIDAR_object)    
LIDAR_object.select = True