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The data structure record is not read correctly with struct.pack and struct.unpack_from

I have this problem in getting data in binary

# Write data
f = open(path, 'wb')

start_date = [2014, 1, 1, 0, 0, 0, 0]
end_date = [2014, 2, 1, 0, 0, 0, 0]

for x in range(10):
    f.write(struct.pack('B', 0))
    f.write(struct.pack('I', x))
    f.write(struct.pack('HBBBBBH', *start_date_binary))
    f.write(struct.pack('HBBBBBH', *end_date_binary))

f.close()

# Read data
f = open(path, 'rb')
for x in range(10):
    data_structure = struct.unpack_from("BIHBBBBBHHBBBBBH",
                                        f.read(FILE_INDEX_STRUCTURE))
    print(data_structure)

f.close()

Output

(0, 0, 2014, 1, 1, 0, 0, 0, 0, 56832, 7, 2, 1, 0, 0, 0)
(0, 17292800, 1, 0, 0, 0, 0, 0, 2014, 258, 0, 0, 0, 0, 0, 0)
(7, 257, 0, 0, 0, 222, 7, 2, 1, 0, 0, 0, 0, 0, 3, 0)
(0, 0, 56832, 7, 2, 1, 0, 0, 0, 0, 0, 4, 0, 0, 0, 2014)
(0, 131989504, 258, 0, 0, 0, 0, 0, 0, 5, 0, 0, 222, 7, 1, 1)
(222, 66055, 0, 0, 0, 0, 0, 6, 0, 56832, 7, 1, 1, 0, 0, 0)
(1, 0, 0, 0, 7, 0, 0, 0, 2014, 257, 0, 0, 0, 0, 0, 56832)
(0, 0, 8, 0, 0, 222, 7, 1, 1, 0, 0, 0, 0, 222, 7, 258)
(0, 2304, 56832, 7, 1, 1, 0, 0, 0, 0, 222, 7, 2, 1, 0, 0)

Expected Result:

(0, 0, 2014, 1, 1, 0, 0, 0, 0, 2014, 2, 1, 0, 0, 0, 0)
(0, 1, 2014, 1, 1, 0, 0, 0, 0, 2014, 2, 1, 0, 0, 0, 0)
(0, 2, 2014, 1, 1, 0, 0, 0, 0, 2014, 2, 1, 0, 0, 0, 0)
(0, 3, 2014, 1, 1, 0, 0, 0, 0, 2014, 2, 1, 0, 0, 0, 0)
(0, 4, 2014, 1, 1, 0, 0, 0, 0, 2014, 2, 1, 0, 0, 0, 0)
(0, 5, 2014, 1, 1, 0, 0, 0, 0, 2014, 2, 1, 0, 0, 0, 0)
(0, 6, 2014, 1, 1, 0, 0, 0, 0, 2014, 2, 1, 0, 0, 0, 0)
(0, 7, 2014, 1, 1, 0, 0, 0, 0, 2014, 2, 1, 0, 0, 0, 0)
(0, 8, 2014, 1, 1, 0, 0, 0, 0, 2014, 2, 1, 0, 0, 0, 0)
(0, 9, 2014, 1, 1, 0, 0, 0, 0, 2014, 2, 1, 0, 0, 0, 0)

EDIT

Getting the type of the structure of the element, where it 'B'is 1 and 'H'equal to 2. Using these types in the same function unpack, the types are confused in the example, where it 'BH'is 3, but returns 4.

>>> struct.unpack_from("B", '')
...
struct.error: unpack_from requires a buffer of at least 1 bytes
>>> struct.unpack_from("H", '')
...
struct.error: unpack_from requires a buffer of at least 2 bytes
>>> struct.unpack_from("BH", '')
...
struct.error: unpack_from requires a buffer of at least 4 bytes
+3
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1 answer

You have problems filling out. As the docs say:

Filling is only automatically added between successive members of the structure. No additive is added at the beginning or end of the encoded structure.

See what happens:

>>> struct.pack("B", 0)
'\x00'
>>> struct.pack("I", 1)
'\x01\x00\x00\x00'
>>> struct.pack("BI", 0, 1)
'\x00\x00\x00\x00\x01\x00\x00\x00'

, , , ...

>>> struct.pack("B0I", 0)
'\x00\x00\x00\x00'

:

>>> struct.pack("=BI", 0, 1)
'\x00\x01\x00\x00\x00'
+6

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