Tuple no attribute error

[oldcity]

Linux Mint 18.2 Python 3.5. Am old time BASIC person.
Help. Have no understanding how to deal with this.
An example please.

 #!/usr/bin/python3
 #
 with open( 'expenses-18', 'r') as yrs_file:
     for line in enumerate(yrs_file):
         (pdate,catg,amt,howp) = line.split(',')
         pdate = str(pdate)
         length = len(pdate)
         catg = int(catg)
         amt = float(amt)
         howp = int(howp)
# Will do stuff here. 
         print pdate, catg, amt, howp

Traceback (most recent call last):
  File "try-me.py", line 5, in <module>
    (pdate,catg,amt,howp) = line.split(',')
AttributeError: 'tuple' object has no attribute 'split'