Another conditional expression candidate (PEP 308)

[Evan]

Roy Smith wrote:
> Why is the else: manditory?  Why not have it return None if none of the 
> conditions are true?

Firstly, because while it is clear to *you* that "if x: 1" will be None 
if 'x' is false, it isn't necessarily clear to someone who is new to 
Python or who never uses conditional expressions.  Your code is now less 
readable.

Secondly, parse this for me (assuming that those who object to mandatory 
parentheses win):

x = if c1: e1 elif c2: if c3: e3 else: e4

Now try:

x = if c1: e1 elif c2: if c3: e3 else: None else: e4

You wouldn't write it without clarifying parens?  Someone would.

My point is that if Guido is going to agree to add this controversial 
new feature to Python, the result should be absolutely 
no-thought-required readable and consistent.  Nothing optional, apart 
from the inherent n-way optionality of the elif: clauses.  No precedence 
questions.  No Corner Case.  Dead simple.

Cheers,

Evan @ 4-am