Joining field works in ArcMap but not in ArcPy?

Question

I am trying to join a field of values found within a DBF to a multi-polyline shapefile. They share a common field name (filename) and the values found within each are identical. I was able to run Join Field without a hitch in ArcMap, but I'm receiving two errors when I try to run it in Python with identical parameters. Here's the block of code:

merge_features = r"C:/Users/kellyj/Desktop/Projects/CostAnalysis/merge_features"
import arcpy
from arcpy import env

arcpy.env.workspace = merge_features
arcpy.AddJoin_management("merged_lines.shp", "filename", "merged_table.dbf", "filename")

These are the errors I receive:

ExecuteError: Failed to execute. Parameters are not valid.
The value cannot be a feature class
ERROR 000840: The value is not a Raster Layer.
ERROR 000840: The value is not a Raster Catalog Layer.
ERROR 000840: The value is not a Mosaic Layer.
WARNING 000970: The join field filename in the join table merged_lines is not indexed. To improve performance, we recommend that an index be created for the join field in the join table.

Any thoughts as to what's happening here?

Answer 1

The input for AddJoin_management needs to be a feature layer, not a shapefile or feature class.

You can get around this by making a feature layer, and then joining that layer to your table. (You'll still get the "not indexed" warning, but that shouldn't prevent the script from executing.)

arcpy.MakeFeatureLayer_management("merged_lines.shp", "tempLayer")
arcpy.AddJoin_management("tempLayer", "filename", "merged_table.dbf", "filename")

Answer 2

You don't specify a version, so I'll just answer based on 10.1 which I 'm using.

First, check the Add Join help file for the function you've used. In particular this part:

The input must be a feature layer, a table view, or a raster layer that has an attribute table; it cannot be a feature class or table.

Then take a look at Join Field.

You appear to be confusing two similar functions.