struct.error: Unpack Requires Buffer of Size

Why This Happens

The struct module packs and unpacks binary data by format strings. Each format character has a fixed byte size. If the buffer is shorter than expected, you get this error.

The Problem

import struct
data = b'\x01\x02'
value = struct.unpack('i', data)  # 'i' expects 4 bytes

The Fix

import struct
data = b'\x01\x02\x03\x04'
value = struct.unpack('i', data)

# Check size first:
expected = struct.calcsize('i')
if len(data) >= expected:
    value = struct.unpack('i', data[:expected])

Step-by-Step Fix

1. 1

   Check format size

   Use struct.calcsize(format) to see expected bytes.

2. 2

   Verify data length

   Check len(data) before unpacking.

3. 3

   Handle partial data

   Read exactly the right number of bytes.