九溪

本页面只读。您可以查看源文件，但不能更改它。如果您觉得这是系统错误，请联系管理员。
====== 使用ArcPy获得矢量数据字段唯一值 ======

按照字段属性筛选，通常要先获取字段唯一值： Unique Values

下面提供两种方法。

===== Example 1: Arcpy Data Access Module using SearchCursor and Set Comprehension =====
<code python getuvalue.py>
import arcpy
import timeit

def unique_values(table, field):  ##uses list comprehension
    with arcpy.da.SearchCursor(table, [field]) as cursor:
        return sorted({row[0] for row in cursor})

try:
    arcpy.env.workspace = r"C:\MTBS_Wildfire\mtbs_perimeter_data"

    start = timeit.default_timer()
    vals = unique_values("mtbs_perims_1984-2015_DD_20170501.shp","Fir_eType")

    stop = timeit.default_timer()
    total_time = stop - start
    print(total_time)
    print(vals)

except Exception as e:
    print("Error: " + e.args[0])
</code>

===== Example 2: Using Numpy with Arcpy =====

<code python getuvalue2.py>
import arcpy
import numpy
import timeit

def unique_values(table, field):  ##uses numpy
    data = arcpy.da.TableToNumPyArray(table, [field])
    return numpy.unique(data[field])

try:
    # mtbs_perims_1984-2015_DD_20170501.shp  - 25,388 recs
    arcpy.env.workspace = r"C:\MTBS_Wildfire\mtbs_perimeter_data"

    start = timeit.default_timer()
    vals = unique_values("mtbs_perims_1984-2015_DD_20170501.shp", "Fi_reType")

    stop = timeit.default_timer()
    total_time = stop - start
    print(total_time)
    print(vals)

except Exception as e:
    print("Error: " + e.args[0])
</code>


参考: 
  - [[http://geospatialtraining.com/get-a-list-of-unique-attribute-values-using-arcpy/|Get a List of Unique Attribute Values using Arcpy]]