Vyper is a Pythonic Smart Contract Language for the Ethereum Virtual Machine. In version 0.3.1 and prior, bytestrings can have dirty bytes in them, resulting in the word-for-word comparisons giving incorrect results. Even without dirty nonzero bytes, two bytestrings can compare to equal if one ends with "\x00" because there is no comparison of the length. A patch is available and expected to be part of the 0.3.2 release. There are currently no known workarounds.