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()
Discussion
Please see http://python.org/peps/pep-0308.html and google for discussions about the ternary operator (if you haven't yet).