Write binary data to file in python3

Question

I've been having a LOT of trouble with this and the other questions don't seem to be what I'm looking for. So basically I have a list of bytes gotten from

bytes = struct.pack('I',4)
bList = list(bytes)
# bList ends up being [0,0,0,4]
# Perform some operation that switches position of bytes in list, etc

So now I want to write this to a file

f = open('/path/to/file','wb')
for i in range(0,len(bList)):
   f.write(bList[i])

But I keep getting the error

TypeError: 'int' does not support the buffer interface

I've also tried writing:

bytes(bList[i]) # Seems to write the incorrect number. 
str(bList[i]).encode()   # Seems to just write the string value instead of byte

Jared Joke · Accepted Answer · 2013-11-21 21:25:09Z

2

Oh boy, I had to jump through hoops to solve this. So basically I had to instead do

bList = bytes()
bList += struct.pack('I',4)

# Perform whatever byte operations I need to

byteList = []

# I know, there's probably a list comprehension to do this more elegantly
for i in range(0,len(bList)):
    byteList.append(bList[i])

f.write(bytes(byteList))

So bytes can take an array of byte values (even if they're represented in decimal form in the array) and convert it to a proper byteArray by casting

answered Nov 21, 2013 at 21:25

Jared Joke

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