Functional Python Programming

The iter() function with a sentinel value

The built-in iter() function creates an iterator over a collection object. We can use this to wrap an iterator object around a collection. In many cases, we'll allow the for statement to handle this implicitly. In a few cases, we might want to create an iterator explicitly so that we can separate the head from the tail of a collection. This function can also iterate through the values created by a callable or function until a sentinel value is found. This feature is sometimes used with the read() function of a file to consume rows until some sentinel value is found. In this case, the given function might be some file's readline() method. Providing a callable function to iter() is a bit hard for us because ...