Unsplit Line (Data Management)


Merges lines that have coincident endpoints and, optionally, common attribute values.


UnsplitLine illustration


  • The attributes of the features that become aggregated by this tool can be summarized or described using a variety of statistics. The statistic used to summarize attributes is added to the output feature class as a single field with the naming standard of statistic type + underscore + input field name. For example, if the SUM statistic is used on a field named POP, the output will have a field named SUM_POP.

  • The availability of physical memory may limit the amount (and complexity) of input features that can be processed and unsplit into a single output line feature. This limitation could cause an error to occur, as the unsplit process may require more memory than is available. To prevent this, Unsplit Line may divide and process the input features using an adaptive tiling algorithm. To determine the features that have been tiled, run the Frequency tool on the result of this tool, specifying the same fields used in the Dissolve Field(s) parameter for the Frequency Field(s) parameter. Any record with a frequency value of 2 has been tiled. Tile boundaries are preserved in the output features to prevent the creation of features that are too large to be used by ArcGIS.


    Running Unsplit Line on the output of a previous unsplit run will rarely reduce the number of features in the output when the original processing divided and processed the inputs using adaptive tiling. The maximum size of any output feature is determined by the amount of available memory at run time; therefore, output containing tiles is an indicator that unsplitting any further with the available resources would cause an out-of-memory situation or result in a feature that is unusable. Additionally, running the Unsplit Line tool a second time on output that was created this way may result in very slow performance for little to no gain and may cause an unexpected failure.

  • Null values are excluded from all statistical calculations. For example, the average of 10, 5, and a null is 7.5 ((10 + 5) / 2). The count returns the number of values included in the statistical calculation, which in this case is 2.


arcpy.management.UnsplitLine(in_features, out_feature_class, {dissolve_field}, {statistics_fields})
ParameterExplanationData Type

The line features to be aggregated.

Feature Layer

The feature class to be created that will contain the aggregated features.

Feature Class

The field or fields on which to aggregate features.

[[field, {statistic_type}],...]

Specifies the numeric field containing attribute values used to calculate the specified statistic. Multiple statistic and field combinations may be specified. Null values are excluded from all statistical calculations.

Text attribute fields can be summarized using first and last statistics. Numeric attribute fields can be summarized using any statistic.

Available statistics types are as follows:

  • SUM—Adds the total value for the specified field.
  • MEAN—Calculates the average for the specified field.
  • MIN—Finds the smallest value for all records of the specified field.
  • MAX—Finds the largest value for all records of the specified field.
  • RANGE—Finds the range of values (maximum minus minimum) for the specified field.
  • STD—Finds the standard deviation on values in the specified field.
  • COUNT—Finds the number of values included in statistical calculations. This counts each value except null values. To determine the number of null values in a field, create a count on the field in question, create a count on a different field that does not contain null values (for example, the OID if present), and subtract the two values.
  • FIRST—Finds the first record in the input and uses its specified field value.
  • LAST—Finds the last record in the input and uses its specified field value.
  • MEDIAN—Calculates the median for all records of the specified field.
  • VARIANCE—Calculates the variance for all records of the specified field.
  • UNIQUE—Counts the number of unique values of the specified field.
Value Table

Code sample

UnsplitLine example (Python window)

The following Python window script demonstrates how to use the UnsplitLine tool in immediate mode.

import arcpy
arcpy.env.workspace = "C:/data/Portland.gdb/Streets"
arcpy.UnsplitLine_management("streets", "C:/output/output.gdb/streets_unsplit",
                             ["STREETNAME", "PREFIX"])
UnsplitLine example 2 (stand-alone script)

The following stand-alone script demonstrates how to use the UnsplitLine tool.

# Name: UnsplitLine_Example2.py
# Description: Unsplit line features based on common attributes
# Import system modules
import arcpy

# Set environment settings
arcpy.env.workspace = "C:/data/Portland.gdb/Streets"
# Set local variables
inFeatures = "streets"
outFeatureClass = "C:/output/output.gdb/streets_unsplit"
dissolveFields = ["STREETNAME", "PREFIX"]
# Execute UnsplitLine using STREETNAME and PREFIX as Dissolve Fields
arcpy.UnsplitLine_management(inFeatures, outFeatureClass, dissolveFields)

Licensing information

  • Basic: No
  • Standard: No
  • Advanced: Yes

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