def chunks(s, n):
    """Produce `n`-character chunks from `s`."""
for start in range(0, len(s), n):
    yield s[start:start + n]
nums = '1.012345e0070.123414e-004-0.1234567891.21423'
for chunk in chunks(nums, 12):
    pass
Разделить строку по количеству символов