games['total_sum'] = games['na_sales'] + games['eu_sales'] + games['jp_sales'] + games['other_sales']
games.head(20)

IndexError                                Traceback (most recent call last)
<ipython-input-42-b15a742c3fc0> in <module>
----> 1 games['total_sum'] = games['na_sales'] + games['eu_sales'] + games['jp_sales'] + games['other_sales']
      2 games.head(20)

/opt/conda/lib/python3.7/site-packages/pandas/core/indexes/base.py in __getitem__(self, key)
   4278         if is_scalar(key):
   4279             key = com.cast_scalar_indexer(key)
-> 4280             return getitem(key)
   4281
   4282         if isinstance(key, slice):

IndexError: only integers, slices (`:`), ellipsis (`...`), numpy.newaxis (`None`) and integer or boolean arrays are valid indices