[Python-ideas] from __future__ import runtime_default_kwargs

[James Lu]

When

from __future__ import runtime_default_kwargs


Is run, 

def a(b=1, c=b+2, d=[]):
    pass

behaves as (if the peephole optimizer didn’t exist)

def a(b=None, c=None):
    if b is None:
        b = 1
    if c is None:
        c = b + 2
    if d is None:
        d = []

i.e. the keyword expression is evaluated at runtime.

Perhaps a restriction on “literals only” can be made so people don’t abuse this.
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