If you too have been personally victimized by Python3’s 'str' object has no attribute 'decode' exception and other string/bytes-related exceptions, I feel your agony. Trauma from such errors have stopped me from using Python3 for code handling buffers, like POCs for vulnerabilities or CTF exploits. Here’s a reference guide on how to convert between Python3’s hexstr/str/bytes/bytearray.

Ultimate Python3 Type Conversion Chart

This has helped me when it was in my personal notes. Hopefully, now it can help you, too.

	have mystr of type str	have myhexstr of type hexstr	have mybytes of type bytes	have mybytearray of type bytearray
want mystr of type str	no change needed	mystr=binascii.unhexlify(myhexstr).decode(<*encoding_see_bottom_note>)	mystr = mybytes.decode(<*encoding_see_bottom_note>)	mystr = mybytearray.decode(<*encoding_see_bottom_note>)
want hexstr of type hexstr	myhexstr = binascii.hexlify(mystr).decode(“utf-8”)	no change needed	myhexstr = binascii.hexlify(bytearray(mybytes)).decode(“utf-8”)	myhexstr = binascii.hexlify(mybytearray).decode(“utf-8”)
want bytes of type bytes	mybytes = mystr.encode()	mybytes = binascii.unhexlify(myhexstr)	no change needed	mybytes = bytes(mybytearray)
want bytearray of type bytearray	mybytearray = bytearray(mystr.encode())	mybytearray = bytearray(binascii.unhexlify(myhexstr))	mybytearray = bytearray(mybytes)	no change needed

*encoding is usually “ascii”/”utf-8” (they’re the same thing), but for non-English character sets, the encoding might be “utf-16”, “utf-32.”

Other Python3 Buffer Need-To-Know

Convert bytes to/from list of ints

Convenient for binary/mathematical operations such as XOR between two buffers

bytes to list of ints

myintlist = list(mybytes)

list of ints to bytes

mybytes = bytes(myintlist)

Read bytes and str from files

Read data from a file as str

Open the file using “r” Example:

mystr = open("C:\whtaguy\orderyogurt.py", "r").read()

Read data from a file as bytes

Open the file using “rb” Example:

mybytes = open("C:\whtaguy\orderyogurt.py", "rb").read()

Python3 Buffer Type Review

str

• Example: mystr = “don’t forget your daily calcium”
• An immutable unicode string
• Created statically using quotes. 

hexstring

• Example: “calc” is “63616c63”
• A str consisting of hexadecimal numbers (0-9, a-f). 
• Primarily used to convert binary data to a printable format. 
• Created like str, but contains only hexadecimal numbers

bytes

• Example: mybytes = b“bring all the boys to the yard”
• An immutable array of one-byte elements
• Created statically by putting the letter “b” before quotes

bytearray

• Example: mybytearray = bytearray(b”I’ll grow up to be in a bytearray”)
• A mutable list of one-byte elements
• Created through the bytearray constructor, which is initialized with a more primitive type (such as bytes, str)