How can I access a variable inside a nested array?

There is an empty list lurking inside userlist.

Try

userlist = [[], ['Number', 'Name', 'Password', 'Balance'], ['1', 'Bob', '12345', '2.34'], ['2', 'Jake', '0000', '2.64']]
for dataset in userlist:
    print(dataset[0])

Output:

Traceback (most recent call last):
  File "C:/Users/wil/AppData/Local/Programs/Python/Python37/zrxtz.py", line 3, in <module>
    print(dataset[0])
IndexError: list index out of range

To fix the problem, use a filter of None to filter out the empty lists:

userlist = [[], ['Number', 'Name', 'Password', 'Balance'], ['1', 'Bob', '12345', '2.34'], ['2', 'Jake', '0000', '2.64']]
userlist = filter(None, userlist)
for dataset in userlist:
    print(dataset[0])

Output:

Number
1
2