Different patterns for TypeError messages are used in the stdlib: expected X, Y found expected X, found Y expected X, but Y found expected X instance, Y found X expected, not Y expect X, not Y need X, Y found X is required, not Y Z must be X, not Y Z should be X, not Y and more. What the pattern is most preferable? Some messages use the article before X or Y. Should the article be used or omitted? Some messages (only in C) truncate actual type name (%.50s, %.80s, %.200s, %.500s). Should type name be truncated at all and for how limit? Type names newer truncated in TypeError messages raised in Python code. Some messages enclose actual type name with single quotes ('%s', '%.200s'). Should type name be quoted? It is uncommon if type name contains spaces.