excel - Errors using arcpy.CalculateField_management

EDIT: What I forgot to mention when I first had this question is that I was trying to do these calculations on a layer which had joins, BUT where the join was on data that was added from an Excel file. ArcGIS does not seem to like data from Excel files.

I am trying to use the arcpy.CalculateField_management function and running into some trouble.

I have a shapefile called district_plans, and to this shapefile I have joined a table of data (the table of data is named kdp). I want to change a field in district_plans to the data in one of the columns of kdp.

Trying the following

arcpy.CalculateField_management("district_plans","district_plans.drawplan", "!kdp$.plan_4!","PYTHON")

yields the following error message

Runtime error  Traceback (most recent call last):   File "", line 1, in
   File "c:\program files x86)\arcgis\desktop10.2\arcpy\arcpy\management.py",

line 3183, in CalculateField     raise e ExecuteError: Failed to execute. Parameters 
are not valid. ERROR 000728: Field district_plans.drawplan does not exist within 
table Failed to execute (CalculateField). 

Trying the following

arcpy.CalculateField_management("district_plans","drawplan", "!kdp$.plan_4!","PYTHON")

yields the following error message

Runtime error  Traceback (most recent call last):   File "", line 1, in 
   File "c:\program files x86)\arcgis\desktop10.2\arcpy\arcpy\management.py", 

line 3183, in CalculateField     raise e ExecuteError: ERROR 999999: Error executing 
function. Failed to execute (CalculateField). 

The following variations all yield errors:

arcpy.CalculateField_management("district_plans","district_plans.drawplan", "!plan_4!","PYTHON")

arcpy.CalculateField_management("district_plans","drawplan", "!plan_4!","PYTHON")

I am able to manually perform the field calculation using the field calculator on the drawplan column in the attribute table of district_plans, so I am not sure why the Python version does not work.

Answer

The issue was that the data joined to the district_plans layer came from an Excel file as pointed out by @Farid Cher and @Michael Miles-Stimson. Although I was not able to get the Table to Table function to work, I found the following code (located in this GitHub repo) which takes a Pandas dataframe and writes it out as a .dbf.

import pysal as ps
import numpy as np

def df2dbf(df, dbf_path, my_specs=None):
    '''
    Convert a pandas.DataFrame into a dbf.
    __author__  = "Dani Arribas-Bel  "
    ...
    Arguments

    ---------
    df          : DataFrame
                  Pandas dataframe object to be entirely written out to a dbf
    dbf_path    : str
                  Path to the output dbf. It is also returned by the function
    my_specs    : list
                  List with the field_specs to use for each column.
                  Defaults to None and applies the following scheme:
                    * int: ('N', 14, 0)
                    * float: ('N', 14, 14)

                    * str: ('C', 14, 0)
    '''
    if my_specs:
        specs = my_specs
    else:
        type2spec = {int: ('N', 20, 0),
                     np.int64: ('N', 20, 0),
                     float: ('N', 36, 15),
                     np.float64: ('N', 36, 15),
                     str: ('C', 14, 0)

        }
        types = [type(df[i].iloc[0]) for i in df.columns]
        specs = [type2spec[t] for t in types]
    db = ps.open(dbf_path, 'w')
    db.header = list(df.columns)
    db.field_spec = specs
    for i, row in df.T.iteritems():
        db.write(row)
    db.close()


    return dbf_path  

After joining the data contained in the .dbf file everything works fine.