Summary
Returns a list of valid transformation methods for converting data from one spatial reference to another. An extent can be used to narrow the list of valid transformation methods for a specific geographic area.
Syntax
ListTransformations (from_sr, to_sr, {extent})| Parameter | Explanation | Data Type | 
from_sr  | The starting geographic coordinate system. Can be specified with a SpatialReference object, the name of the spatial reference, or a path to a projection file (.prj).  | SpatialReference | 
to_sr  | The final geographic coordinate system. Can be specified with a SpatialReference object, the name of the spatial reference, or a path to a projection file (.prj).  | SpatialReference | 
extent  | Only transformations that span the entire extent will be returned. The extent needs to be specified in coordinates from the in_sr. When working with data, the extent on a Describe object can be used.  | Extent | 
| Data Type | Explanation | 
| String | A list of valid transformation methods.  | 
Code sample
Use ListTransformations to identify valid transformations for projecting from one coordinate system to another.
import arcpy
from_sr = arcpy.SpatialReference('WGS 1984')
to_sr = arcpy.SpatialReference('NAD 1927 StatePlane California VI FIPS 0406')
extent = arcpy.Extent(-178.217598182, 18.9217863640001,
                      -66.969270909, 71.4062354550001)
transformations = arcpy.ListTransformations(from_sr, to_sr, extent)