Correct way to change bytes in a file?

[Raptor88]

I started a different thread named "What is actually strored in memory?" but after 93 views, no answers so I'll present my actual task to hopefully get some answers.
(EDIT:  Opps, I see now that there are answers to that thread.  Thanks for those replies.  But please help me with this thread.  Thanks from a newbie.)

I want to read a file into memory, change some bytes in the memory data, then write the memory data to a new file.  I will not be "inserting" bytes but just changing byte values.  Here's some sample code:

with open("test 18.vf", "rb") as bfile:     # Just opens the file. Does not read the file.
    bdata = bfile.read()

bdata[2] = 10
TypeError: 'bytes' object does not support item assignment

I learned that "bdata" is a "bytes" type so is immutable.  If I convert "bdata" using the list() method, then I can change bytes without error.  Here's an example:

with open("test 18.vf", "rb") as bfile:     # Just opens the file. Does not read the file.
    bdata = bfile.read()

tmpdata = list(bdata)
tmpdata[2] = 10     

# This works with no errors

So after the bytes are changed in "tmpdata", is it correct that I need to convert it back to "bytes" data using this code:
.... bdata = bytes(tmpdata)
and then write bdata to a new file?

Or is my logic wrong or using unnecessary steps?