FieldMappings—ArcGIS Pro

Zusammenfassung

The FieldMappings object is a collection of FieldMap objects and it is used as the parameter value for tools that perform field mapping, such as Merge.

Diskussion

Die Eigenschaften des FieldMap-Objekts enthalten die Anfangs- und die Endposition eines Eingabetextwertes, sodass ein Ausgabewert mit einem Teil eines Eingabewertes erstellt werden kann. Wenn ein FieldMap-Objekt mehrere Eingabefelder aus derselben Tabelle oder Feature-Class enthält, werden die Werte aller Datensätze unter Verwendung der Eigenschaft mergeRule zusammengeführt. Dies ist eine benutzerfreundliche Möglichkeit zum Verbinden von Werten, beispielsweise eines Straßennamens in einem Feld und einer Straßenart, die in einem anderen Feld enthalten ist (z. B. "Eureka" und "Street"). Die Eigenschaft joinDelimiter von FieldMap wird verwendet, wenn für mergeRule der Wert Join angegeben wird. Als Trennzeichen können beliebige Zeichen verwendet werden, beispielsweise Leerzeichen. Im obigen Beispiel würde damit der Wert "Eureka Street" erstellt.

Das FieldMappings-Objekt ist eine Sammlung von FieldMap-Objekten und wird als Parameterwert für Werkzeuge für die Feldzuordnung verwendet, beispielsweise Zusammenführen (Merge). Sie können am einfachsten mit diesen Objekten arbeiten, indem Sie zuerst ein FieldMappings-Objekt erstellen und dann die zugehörigen FieldMap-Objekte initialisieren, indem Sie die zu kombinierenden Eingabe-Feature-Classes oder Tabellen hinzufügen. Wenn alle Eingaben bereitgestellt wurden, enthält das FieldMappings-Objekt ein FieldMap-Objekt (bzw. ein Ausgabefeld) für jeden eindeutigen Feldnamen aus allen Eingaben. Sie können diese Liste ändern, indem Sie neue Felder hinzufügen, die Eigenschaften oder den Inhalt von Ausgabefeldern ändern oder unerwünschte Ausgabefelder entfernen.

Syntax

 FieldMappings  ()

Eigenschaften

Eigenschaft	Erläuterung	Datentyp
fieldCount (Schreibgeschützt)	The number of output fields.	Integer
fieldMappings (Lesen und schreiben)	A list of FieldMap objects that make up the FieldMappings object.	FieldMap
fieldValidationWorkspace (Lesen und schreiben)	The workspace type that defines the rules for attribute field naming. These rules are used when determining the output field names, which are based on the names of the input fields. For example, setting the fieldValidationWorkspace property to the path of a folder on disk containing the input shapefiles will result in the output field names being truncated to 10 characters. Setting the fieldValidationWorkspace property to the path of a file geodatabase will allow for much longer field names. The fieldValidationWorkspace property should be set with a consideration for the output format.	String
fields (Schreibgeschützt)	A list of Field objects. Each field object represents the properties of each output field.	Field

Methodenübersicht

Methode	Erläuterung
addFieldMap (field_map)	Add a field map to the field mappings.
addTable (table_dataset)	Adds a table to the field mappings object.
exportToString ()	Exports the object to its string representation.
findFieldMapIndex (field_map_name)	Find a field map within the field mappings by name.
getFieldMap (index)	Returns a FieldMap object from the FieldMappings object by index position.
loadFromString (string)	Defines a FieldMappings object from a formatted string.
removeAll ()	Removes all values and creates an empty object.
removeFieldMap (index)	Removes a FieldMap object from the FieldMappings object.
replaceFieldMap (index, value)	Replace a FieldMap object within the FieldMappings object.

Methoden

addFieldMap (field_map)

Parameter	Erläuterung	Datentyp
field_map	The field map to add to the field mappings	FieldMap

addTable (table_dataset)

Parameter	Erläuterung	Datentyp
table_dataset	The table to add to the field mappings object.	String

exportToString ()

Rückgabewert

Datentyp	Erläuterung
String	The string representation of the object.

findFieldMapIndex (field_map_name)

Parameter	Erläuterung	Datentyp
field_map_name	Find the field map by name.	String

Rückgabewert

Datentyp	Erläuterung
Integer	The index position of the field map.

getFieldMap (index)

Parameter	Erläuterung	Datentyp
index	The index position of the FieldMap object.	Integer

Rückgabewert

Datentyp	Erläuterung
FieldMap	The FieldMap object from the FieldMappings object.

loadFromString (string)

Parameter Erläuterung Datentyp

Parameter	Erläuterung	Datentyp
string	The string representation of the object. In addition to FieldMappings and FieldMap methods and properties, you can also construct a FieldMappings object from a formatted string. The following example shows the creation of a FieldMappings object that could be used with the Merge tool. `import arcpy fieldmappings_string = 'REGION "Region" true true false 21 Text -1 -1,First,#,c:\\data\\fgdb.gdb\\north_america,REGION,-1,-1,c:\\data\\fgdb.gdb\\south_america,REGION2,-1,-1' fieldmappings = arcpy.FieldMappings() fieldmappings.loadFromString(fieldmappings_string)` The first nine values in the string define an output field and are space delimited. The name of the output field. The alias of the output field. Whether the output field is editable (true or false). Whether the output field supports nulls (true or false). Whether the output field is required (true or false). The length of the output field (text fields only). The field type of the output field. The precision of the output field (float and double fields only). The scale of the output field (float and double fields only). The remaining values define the field map characteristics and are comma delimited. The field map merge rule. The concatenator to join values. The path to the input table. The field name from the input table. The start position of an input text value. The end position of an input text value. Any number of input fields can be mapped to the output field, not only two, as implied in the example. Include the merge rule and concatenator once, and include the dataset path, field name, and start position and end position for each input field. Enclose any values with spaces, such as the field alias or concatenator, in quotation marks. To skip a value, use a # for string values, and -1 for numeric values. As shown in the following example, use a semicolon delimiter to separate multiple output fields. `import arcpy fieldmappings_string = 'REGION "Region" true true false 21 Text -1 -1,First,#,c:\\data\\fgdb.gdb\\north_america,REGION,-1,-1,c:\\data\\fgdb.gdb\\south_america,REGION2,-1,-1;CAPITAL "Capital" true true false 21 Text -1 -1,First,#,c:\\data\\fgdb.gdb\\north_america,CAPITAL,-1,-1,c:\\data\\fgdb.gdb\\south_america,CAPITAL2,-1,-1' fieldmappings = arcpy.FieldMappings() fieldmappings.loadFromString(fieldmappings_string)`	String

string

The string representation of the object.

In addition to FieldMappings and FieldMap methods and properties, you can also construct a FieldMappings object from a formatted string.

The following example shows the creation of a FieldMappings object that could be used with the Merge tool.

import arcpy

fieldmappings_string = 'REGION "Region" true true false 21 Text -1 -1,First,#,c:\\data\\fgdb.gdb\\north_america,REGION,-1,-1,c:\\data\\fgdb.gdb\\south_america,REGION2,-1,-1'

fieldmappings = arcpy.FieldMappings()
fieldmappings.loadFromString(fieldmappings_string)

The first nine values in the string define an output field and are space delimited.

The name of the output field.
The alias of the output field.
Whether the output field is editable (true or false).
Whether the output field supports nulls (true or false).
Whether the output field is required (true or false).
The length of the output field (text fields only).
The field type of the output field.
The precision of the output field (float and double fields only).
The scale of the output field (float and double fields only).

The remaining values define the field map characteristics and are comma delimited.

The field map merge rule.
The concatenator to join values.
The path to the input table.
The field name from the input table.
The start position of an input text value.
The end position of an input text value.

Any number of input fields can be mapped to the output field, not only two, as implied in the example. Include the merge rule and concatenator once, and include the dataset path, field name, and start position and end position for each input field.

Enclose any values with spaces, such as the field alias or concatenator, in quotation marks.

To skip a value, use a # for string values, and -1 for numeric values.

As shown in the following example, use a semicolon delimiter to separate multiple output fields.

import arcpy

fieldmappings_string = 'REGION "Region" true true false 21 Text -1 -1,First,#,c:\\data\\fgdb.gdb\\north_america,REGION,-1,-1,c:\\data\\fgdb.gdb\\south_america,REGION2,-1,-1;CAPITAL "Capital" true true false 21 Text -1 -1,First,#,c:\\data\\fgdb.gdb\\north_america,CAPITAL,-1,-1,c:\\data\\fgdb.gdb\\south_america,CAPITAL2,-1,-1'

fieldmappings = arcpy.FieldMappings()
fieldmappings.loadFromString(fieldmappings_string)

String

removeAll ()

removeFieldMap (index)

Parameter	Erläuterung	Datentyp
index	The index position of the FieldMap.	Integer

replaceFieldMap (index, value)

Parameter	Erläuterung	Datentyp
index	The index position of the FieldMap object to be replaced.	Integer
value	The replacement FieldMap object.	FieldMap

Codebeispiel

FieldMappings example

FieldMap-Objekte werden oft dazu verwendet, um ähnliche Datasets in ein einzelnes umfassendes Dataset zusammenzuführen. In diesem Beispiel werden die Feature-Class Trees und das Shapefile Plants.shp in eine Feature-Class namens Vegetation zusammengeführt. Die ursprünglichen Feature-Classes verfügen jeweils über zwei Attribute: Type und Diameter. Diese beiden Attribute müssen bei der Zusammenführung beibehalten werden.

import arcpy
# Set the workspace
arcpy.env.workspace = 'c:/base'
in_file1 = 'data.gdb/Trees'
in_file2 = 'Plants.shp'
output_file = 'data.gdb/Vegetation'
# Create the required FieldMap and FieldMappings objects
fm_type = arcpy.FieldMap()
fm_diam = arcpy.FieldMap()
fms = arcpy.FieldMappings()
# Get the field names of vegetation type and diameter for both original
# files
tree_type = "Tree_Type"
plant_type = "Plant_Type"
tree_diam = "Tree_Diameter"
plant_diam = "Diameter"
# Add fields to their corresponding FieldMap objects
fm_type.addInputField(in_file1, tree_type)
fm_type.addInputField(in_file2, plant_type)
fm_diam.addInputField(in_file1, tree_diam)
fm_diam.addInputField(in_file2, plant_diam)
# Set the output field properties for both FieldMap objects
type_name = fm_type.outputField
type_name.name = 'Veg_Type'
fm_type.outputField = type_name
diam_name = fm_diam.outputField
diam_name.name = 'Veg_Diam'
fm_diam.outputField = diam_name
# Add the FieldMap objects to the FieldMappings object
fms.addFieldMap(fm_type)
fms.addFieldMap(fm_diam)
# Merge the two feature classes
arcpy.Merge_management([in_file1, in_file2], output_file, fms)

FieldMappings example 2

In diesem Beispiel wird eine Möglichkeit gezeigt: Mithilfe von FieldMap-Objekten und dem Werkzeug FeatureClassToFeatureClass können Felder zusammengeführt werden. In diesem Beispiel enthält eine Feature-Class Informationen zur Anzahl von Unfällen pro Kreuzung in einer Stadt. Ein Feld enthält dabei die Daten für ein Jahr. Der Benutzer möchte nun für jede Kreuzung die durchschnittliche Anzahl an Unfällen bestimmen, ohne die vorhandene Tabelle zu ändern.

import arcpy
# Set the workspace arcpy.env.workspace = 'c:/base/data.gdb'
in_file = 'AccidentData' out_file = 'AverageAccidents'
# Create the necessary FieldMap and FieldMappings objects fm = arcpy.FieldMap() fm1 = arcpy.FieldMap() fms = arcpy.FieldMappings()
# Each field with accident data begins with 'Yr' (from Yr2007 to Yr2012). # The next step loops through each of the fields beginning with 'Yr', # and adds them to the FieldMap Object for field in arcpy.ListFields(in_file, 'Yr*'):
    fm.addInputField(in_file, field.name)
# Set the merge rule to find the mean value of all fields in the
# FieldMap object fm.mergeRule = 'Mean'
# Set properties of the output name. f_name = fm.outputField f_name.name = 'AvgAccidents' f_name.aliasName = 'AvgAccidents' fm.outputField = f_name
# Add the intersection field to the second FieldMap object fm1.addInputField(in_file, "Intersection")
# Add both FieldMaps to the FieldMappings Object fms.addFieldMap(fm) fms.addFieldMap(fm1)
# Create the output feature class, using the FieldMappings object arcpy.FeatureClassToFeatureClass_conversion(    in_file, arcpy.env.workspace, out_file, field_mapping=fms)

Zusammenfassung

Diskussion

Syntax

Eigenschaften

Methodenübersicht

Methoden

Codebeispiel

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