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The PyMonad Library

A monad allows us to impose an order on an expression evaluation in an otherwise lenient language. We can use a monad to insist that an expression such as a + b + c is evaluated in left-to-right order. This can interfere with the compiler’s ability to optimize expression evaluation. This is necessary, however, when we want files to have their content read or written in a specific order: a monad is a way to assure that the read() and write() functions are evaluated in a particular order.

Languages that are lenient and have optimizing compilers benefit from monads imposing order on the evaluation of expressions. Python, for the most part, is strict and does not optimize, meaning there are few practical requirements for monads in Python.

While the PyMonad package contains a variety of monads and other functional tools, much of the package was designed to help folks understand functional programming using Python syntax. We’ll...