TableOfContents

The Problem

Python is sorely missing an if statement that:

• computes and takes the value of A if and only if the predicate is true
• computes and takes the value of B if and only if the predicate is false

In C and its derivitives,

predicate ? A : B 

This is extremely useful in programming and helps avoid copy and paste assignments. This is an example of poor code, because the assignment logic "x=" is copied and pasted, violating the software maintainbility and readability principle of OnceAndOnlyOnce:

if test:
   x=sin(cos(x))
else:
   x=cos(sin(x))

See also SwitchStatement

Current Python Idioms

There are a few ways in Python do achieve the evaluation only of the statement used when the predicate is true:

Proposed Solutions

If always returns a value

x = if test:
    A()
 else:
     B()