Problem to convert act format to CSV a bytes-like object is required, not 'str'

Question

I have a problem converting an .act file to csv format. I am using this code:

import struct
import csv

DATA = []

with open("modis_lst.act", "rb") as actFile:
    for _ in range(256):
        raw = actFile.read(3)
        color = struct.unpack("3B", raw)
        DATA.append(color)


with open('test.csv', 'wb') as csvfile:
   csvWriter = csv.writer(csvfile)
   csvWriter.writerows(DATA)

but I get the following ERROR: a bytes-like object is required, not 'str'

Answer 1

I mocked up what I think you're working with:

import struct
import csv

DATA = []

raw = struct.pack("3B", 255, 0, 0)
color = struct.unpack("3B", raw)

DATA.append(color)

with open("test.csv", "wb") as csvfile:
    csvWriter = csv.writer(csvfile)
    csvWriter.writerows(DATA)

and I too get:

  File "/users/z/main.py", line 15, in <module>
    csvWriter.writerows(DATA)
TypeError: a bytes-like object is required, not 'str'

And this is because opening the file as binary (wb) is wrong in this case: you've already decoded the binary structure into strings, so open the file as plain text and pass that to the CSV writer:

with open("test.csv", "w") as csvfile:

and now my test.csv file looks correct:

255,0,0

P.S. I don't know when opening a file as binary for writing CSV is correct... I've never thought of that before :)