$ python
Python 3.7.4 (default, Aug 13 2019, 15:17:50) 
[Clang 4.0.1 (tags/RELEASE_401/final)] :: Anaconda, Inc. on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import gzip
>>> with gzip.open("ex1.bam", "rb") as handle: raw_bytes = handle.read()
... 
>>> with gzip.open("ex1.bam", "rt") as handle: open_as_text = handle.read()
... 
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Users/xxx/miniconda3/lib/python3.7/codecs.py", line 322, in decode
    (result, consumed) = self._buffer_decode(data, self.errors, final)
UnicodeDecodeError: 'utf-8' codec can't decode byte 0x84 in position 100: invalid start byte
>>> with gzip.open("ex1.bam", "rt", encoding="latin1") as handle: open_as_latin1 = handle.read()
... 
>>> len(raw_bytes)
456614
>>> len(raw_bytes.decode("latin1"))
456614
>>> len(open_as_latin1)
456610
>>> raw_bytes.decode("latin1").replace("\r\n", "\n").replace("\r", "\n") == open_as_latin1
True
>>>