This Python tutorial explains Choose Endianness When Writing Binary Formats. Follow the example, inspect the output, and practise an input change so you understand the behavior rather than simply copying the syntax.
What This Feature Does
Choose how multibyte numbers are ordered in a file or network format.
Little-endian stores the least significant byte first; big-endian stores the most significant byte first. When using int.to_bytes() or struct, declare the byte order and use the same order when reading.
When to Use It
This technique belongs to binary data and byte operations. It is useful when the input, operation and expected outcome are known. Start with a small controlled example before integrating it into a larger workflow.
Step-by-Step Python Example
Read the code once before running it. Notice which values are inputs, which function or method performs the work, and whether the result is returned or stored by changing an existing object.
measurement_value = 0x1234
print(measurement_value.to_bytes(2, "big").hex())
print(measurement_value.to_bytes(2, "little").hex())
print(int.from_bytes(b"\x12\x34", "big"))Understanding the Code
- Find the call print(measurement_value.to_bytes(2, "big").hex()). Its parameters determine the specific operation demonstrated in the title.
- Its purpose is to choose how multibyte numbers are ordered in a file or network format. Compare this description against the result printed by the program.
- The print() expressions display a checkable outcome. Print values and exception names are not substitutes for the program result itself.
Expected Output
1234
3412
4660Each printed line corresponds to a separate observation in the program. Use the lines to distinguish returned data, changes to existing objects, and status checks.
Important Details and Edge Cases
The byte order matters only for values spanning multiple bytes; it must be part of the documented binary format.
Bytes are not the same as text. Decide whether a value represents encoded characters or a binary record, and document its length, byte order and input assumptions before exchanging it with another program.
Second Example: A Useful Variation
import struct
print(struct.pack('>H', 258).hex())
print(struct.pack('<H', 258).hex())Both results encode the same unsigned number, but the two bytes appear in opposite orders.
Variation Output
0102
0201Practice: Try It Yourself
Encode 0xABCD in both byte orders and examine each byte.
Begin by copying the example into a separate practice file. Change one input at a time, run it again, and describe why the result changed. If the exercise writes or deletes files, keep it inside a temporary test folder.
Official Python Documentation
For the complete reference, see the Python standard library documentation.
Common Beginner Mistakes
- Writing in little-endian order and decoding as big-endian without noticing the changed value.
- Assuming network protocols all use the machine native byte order.
- Bytes are not the same as text. Decide whether a value represents encoded characters or a binary record, and document its length, byte order and input assumptions before exchanging it with another program.
Key Takeaways
- Choose how multibyte numbers are ordered in a file or network format.
- Little-endian stores the least significant byte first; big-endian stores the most significant byte first. When using int.to_bytes() or struct, declare the byte order and use the same order when reading.
- Avoid this common pitfall: Writing in little-endian order and decoding as big-endian without noticing the changed value.