struct.pack in Python3 got struct.error: required argument is not an integer

Question

I'm doing a zipping func of this:

open_file = open(file_path,'rb')
open_save = open(save_path,'wb+')
try:
    open_read = open_file.read()
    data = zip_data(open_read)

    head_xis = b'XIS'
    head_version = bytes(0)
    head_type1 = bytes(1)
    head_type2 = bytes(1)
    head_en_type = bytes(0)
    head_com_type = bytes(1)
    head_sour_len = len(open_read)

    # try:
    md5 = hashlib.md5()
    md5.update(open_read)
    head_md5 = md5.digest()
    print("byteeeeee")
    # except:
    #     head_md5 = None
    randoms = str(uuid.uuid1()).split('-')[0]
    head_random = bytes(randoms,encoding = "utf-8")
    print(head_md5)
    print(head_random)
    head_resour_len= len(data)

    print(type(head_xis))
    print(type(head_version))
    print(type(head_type1))
    print(type(head_type2))
    print(type(head_en_type))
    print(type(head_com_type))
    print(type(head_sour_len))
    print(type(head_md5))
    print(type(head_random))
    print(type(head_resour_len))

    head = struct.pack('3sBBBBBI16s8sI',
                        head_xis,
                        head_version,
                        head_type1,
                        head_type2,
                        head_en_type,
                        head_com_type,
                        head_sour_len,
                        head_md5,
                        head_random,
                        head_resour_len
                        )
    open_save.write(head)

# except Exception as e:
#     print("eeeee" + str(e))
#     return False,str(e)
# else:
#     open_save.write(data)
#     return True,''
finally:
    open_file.close()
    open_save.close()

and it shows exception and print like below:

byteeeeee
b'\xf9\xf4\xf2\xcb\xbfM\x11\xb5\xeeNP/\x02H\xebK'
b'f9f33502'
class 'bytes'
class 'bytes'
class 'bytes'
class 'bytes'
class 'bytes'
class 'bytes'
class 'int'
class 'bytes'
class 'bytes'
class 'int'
Traceback (most recent call last):
  File "entrance.py", line 52, in startProcess
    Helper.processCombine(self.selectedVer,False)
  File "/Users/mapzchen/myShell/qtPro/fastColuaco/Helper.py", line 86, in processCombine
    itemConf.get(version,suffix),True,True)
  File "/Users/mapzchen/myShell/qtPro/fastColuaco/coluaco.py", line 514, in process
    compress(build_dir,zip_dir,filter_file)
  File "/Users/mapzchen/myShell/qtPro/fastColuaco/coluaco.py", line 400, in compress
    zfile = zip_file(src_file_path,save_path)
  File "/Users/mapzchen/myShell/qtPro/fastColuaco/coluaco.py", line 131, in zip_file
    head_resour_len
struct.error: required argument is not an integer

I have tried to print types of arguments, and it seems to fit 3sBBBBBI16s8sI correctly I'm confused by what arg that performs this exception

Answer 1

In structure formating string "B" for bytes need variable type 'int', that is main problem. So instead of head_type1 = bytes(1) use head_type1 = 1

Here given below code gives same error.

Problem:

    n = bytes(2)
    x = struct.pack("B", n)

Solution:

    n = 2
    x = struct.pack("B", n)

Suggestion: Use Byte Orders like '=', while dealing with integers like 'I'.