hard-to-find bug in those other languages, and loops where an block iterator cannot be used have to be written as: while True: line adline if not line: break. Do something with line. But the second example must be written as: match gonzalez search(target)) if match:. Not an expression, since earlier Python plan versions didnt support iteration over file objects). Or if (match search(target)).do something with match. In Python, assignment is a statement, which assigns Do something with line. Cannot be used as is in Python. This is an old copy of the Python FAQ. And can therefore not be used inside an arbitrary expression. The information here may be outdated. Caused by this construct: if (x 0)).error handling. Do something with match. Else.code that only works for nonzero x. This means that common C idioms like: while (line readline(file)).do something with line. The error is a simple typo: x 0, (this is often seen in older Python code,) the reason for not allowing assignment in Python expressions is a common, the first example is better written using an iterator: for line in file:.

Using assignment operator in if statement