4.2.1 Vector data processing¶

Basic information about data sources provides Describe. In the case below Feature Class and Table properties are accessed.

In [19]:

nuts_path = r"S:\K155\Public\155ISDP\01\NUTS_RG_20M_2021_3035.shp"
nuts = arcpy.Describe(nuts_path)
nuts.shapeType

nuts_path = r"S:\K155\Public\155ISDP\01\NUTS_RG_20M_2021_3035.shp" nuts = arcpy.Describe(nuts_path) nuts.shapeType

Out[19]:

'Polygon'

Fields and their properties can be accessed via fields property (see Table).

In [20]:

len(nuts.fields)

len(nuts.fields)

Out[20]:

11

In [21]:

for field in nuts.fields:
    print(field.name, field.type)

for field in nuts.fields: print(field.name, field.type)

FID OID
Shape Geometry
NUTS_ID String
LEVL_CODE SmallInteger
CNTR_CODE String
NAME_LATN String
NUTS_NAME String
MOUNT_TYPE SmallInteger
URBN_TYPE SmallInteger
COAST_TYPE SmallInteger
FID_1 String

Data records (rows in attribute table) may be provided by SearchCursor.

In [22]:

rows = arcpy.SearchCursor(nuts_path)
for row in rows:
    print(row.CNTR_CODE)
    break

rows = arcpy.SearchCursor(nuts_path) for row in rows: print(row.CNTR_CODE) break

FR

In [23]:

code = 'CZ'
count = 0
rows = arcpy.SearchCursor(nuts_path)
for row in rows:
    if row.CNTR_CODE == code:
        count += 1
print(f'Number of features with code {code}: {count}')

code = 'CZ' count = 0 rows = arcpy.SearchCursor(nuts_path) for row in rows: if row.CNTR_CODE == code: count += 1 print(f'Number of features with code {code}: {count}')

Number of features with code CZ: 24

Geometry may be accessed via SHAPE attribute.

In [24]:

area = 0
rows = arcpy.SearchCursor(nuts_path, f"CNTR_CODE = '{code}' AND LEVL_CODE=2")
for row in rows:
    area += row.SHAPE.area
print(f"{code} area in km2: {area/1e6}")

area = 0 rows = arcpy.SearchCursor(nuts_path, f"CNTR_CODE = '{code}' AND LEVL_CODE=2") for row in rows: area += row.SHAPE.area print(f"{code} area in km2: {area/1e6}")

CZ area in km2: 78896.87190870794

Let's collect all country codes.

In [25]:

codes = []
rows = arcpy.SearchCursor(nuts_path)
count = 0
for row in rows:
    if row.CNTR_CODE not in codes:
        codes.append(row.CNTR_CODE)
print(sorted(codes))

codes = [] rows = arcpy.SearchCursor(nuts_path) count = 0 for row in rows: if row.CNTR_CODE not in codes: codes.append(row.CNTR_CODE) print(sorted(codes))

['AL', 'AT', 'BE', 'BG', 'CH', 'CY', 'CZ', 'DE', 'DK', 'EE', 'EL', 'ES', 'FI', 'FR', 'HR', 'HU', 'IE', 'IS', 'IT', 'LI', 'LT', 'LU', 'LV', 'ME', 'MK', 'MT', 'NL', 'NO', 'PL', 'PT', 'RO', 'RS', 'SE', 'SI', 'SK', 'TR', 'UK']

Tip: Use set instead of list.

Perform ArcGIS tools¶

ArcPy allows to run any tool which is possible to run through graphical user interface. In the example bellow Select tool is demonstrated. Tip: Check the tool manual page for example of Python usage.

In [26]:

import os
arcpy.env.overwriteOutput = True
arcpy.env.workspace = r"C:\Users\martin\Documents\isdp_04" # change path here
if not os.path.exists(arcpy.env.workspace):
    os.makedirs(arcpy.env.workspace)
    
for code in sorted(codes)[:3]:
    print("{}...".format(code))
    arcpy.analysis.Select(nuts_path, f"nuts_{code}.shp", f"CNTR_CODE = '{code}' AND LEVL_CODE = 2")

import os arcpy.env.overwriteOutput = True arcpy.env.workspace = r"C:\Users\martin\Documents\isdp_04" # change path here if not os.path.exists(arcpy.env.workspace): os.makedirs(arcpy.env.workspace) for code in sorted(codes)[:3]: print("{}...".format(code)) arcpy.analysis.Select(nuts_path, f"nuts_{code}.shp", f"CNTR_CODE = '{code}' AND LEVL_CODE = 2")

AL...
AT...
BE...

The code above creates for each country separated Shapefile. Now let's dissolve NUTS regions to level 0 (one region for each country).

In [27]:

for code in sorted(codes)[:3]:
    print("{}...".format(code))
    arcpy.management.Dissolve(f"nuts_{code}.shp", f"nuts0_{code}.shp", "CNTR_CODE")

for code in sorted(codes)[:3]: print("{}...".format(code)) arcpy.management.Dissolve(f"nuts_{code}.shp", f"nuts0_{code}.shp", "CNTR_CODE")

AL...
AT...
BE...