How to insert null decimals / datetime into MYSQL from python?

I have the data file:

'Laura', 'Laura Ellenburg', '5342 Picklied Trout Lane', 'Nashville', 'TN',
'38010','2000-02-22', ' ', '454-56-768'

Notice the ' ' near the end.

I am using the python code:

  data = []
  infile = open ("./BIGPVFC-ASC10e/Employee.asc", "r")
  for line in infile:
    line = line.rstrip("\n")
    line = line.strip()
    seq = line.split(", ")
    for i in range(0,9):
      seq[i] = seq[i].strip("'")
    seq = tuple (seq)
    data.append(seq)
  infile.close()

  cursor.executemany ("""insert into PV_employee
  (employeeid, employeename, employeeaddress, employeecity, employeestate,
   employeezip, employeedatehired, employeebirthdate, employeesupervisor)
   values (%s, %s, %s, %s, %s, %s, %s, %s, %s)""", data)

The table I have is:

create table PV_employee
 (employeeid         varchar(10)    not null
 ,employeename       varchar(25)    null
 ,employeeaddress    varchar(30)    null
 ,employeecity       varchar(20)    null
 ,employeestate      char(2)        null
 ,employeezip        varchar(10)         null  
 ,employeedatehired  datetime       null
 ,employeebirthdate  datetime      null
 ,employeesupervisor varchar(10)    null
 ,primary key (employeeid)
);

where I get the error "Warning: Out of Range value for column ....."

In the case of null decimals I get "Warning: incorrect decimal value: ' ' for column ... "

I have tried change the ' ' to '', 'NULL', and NULL. None of these seem to work. Any suggestions?