Tools that honor the Output has M Values environment will control whether the output geodataset will store m-values.
Usage notes
- Feature vertices that do not have an m-value will be assigned a value of NaN (Not a Number).
 - For shapefiles, storage of m- and z-values is closely connected; if the output has z-values, then regardless of this environment setting, the output will also have m-values.
 
Dialog syntax
- Same as Input—If the input has m-values, the output will also have m-values. If the input does not have m-values, the output will not have m-values. This is the default value.
 - Enabled—The output will have m-values.
 - Disabled—The output will not have m-values.
 
Scripting syntax
arcpy.env.outputMFlag = output_m_flag
| output_m_flag | Explanation | 
|---|---|
Same As Input  | If the input has m-values, the output will have m-values. If it does not have m-values, the output will not have m-values. This is the default.  | 
Enabled  | The output will have m-values.  | 
Disabled  | The output will not have m-values.  | 
Script example
import arcpy
# Set the outputMFlag environment to Enabled
arcpy.env.outputMFlag = "Enabled"