Missing commas and Python automatic string concatenation

gistfile1.py

# omitting a comma after the second field
# does not generate an error
fields = [
  'field1',
  'field2'
  'field3'
]

# in fact 
'field1' 'field2' == 'field1field2'

# so the list effectively becomes
fields = [
  'field1',
  'field2field3'
]