a = b"Hello, world!" # bytes object
b = "Hello, world!" # str object
# 字符串转字节 str --> bytes
print(str.encode(b)) # 默认 encoding="utf-8"
print(bytes(b, encoding="utf8"))
print(b.encode()) # 默认 encoding="utf-8"
# 字节转字符串 bytes --> str
print(bytes.decode(a)) # 默认encoding="utf-8"
print(str(a, encoding="utf-8"))
print(a.decode()) # 默认 encoding="utf-8"