Beginner trying to run simple code

[Larz60+]

On the items you have tried (you may have to re-try), please include all error output.
Your number of arguments is correct (program looks for three, 1st one is always the program name)
The order is input file name, output file name
You could place print statements in various strategic locations to see if data looks appropriate,
for example:

• After line 15 add

  print('line: {}'.format(line))

• After line number 19

  print('tokens: {}'.format(tokens))

• etc.
  

Copy all penitent data (only small sample of large data, please) and report your findings.