base64 encoding of file in Python

Question

I want to use the function base64.encode() to directly encode the contents of a file in Python.

The documentation states:

base64.encode(input, output)

Encode the contents of the binary input file and write the resulting base64 encoded data to the output file. input and output must be file objects.

So I do this:

encode(open('existing_file.dat','r'), open('output.dat','w'))

and get the following error:

>>> import base64
>>> base64.encode(open('existing_file.dat','r'), open('output.dat','w'))
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.6/base64.py", line 502, in encode
    line = binascii.b2a_base64(s)
TypeError: a bytes-like object is required, not 'str'

To my eye that looks like a bug in /usr/lib/python3.6/base64.py but a big part of me does not want to believe that...

Answer 1

from docs

when opening a binary file, you should append 'b' to the mode value to open the file in binary mode

so changing

encode(open('existing_file.dat','r'), open('output.dat','w'))

to

encode(open('existing_file.dat','rb'), open('output.dat','wb'))

should work