[issue12473] factory func of collections.defaultdict should receive the "missing key" as args when called.

[HaiYun Yan]

New submission from HaiYun Yan :

for example:

def calc(params):
""" i am factoring numbers. """
# an expensive CPU cost function but 
# passin params and return result are both lightweight

cachedcalc = collections.defaultdict(calc)
result = cachedcalc[0xFFF0AC0FFF1]

--
components: Library (Lib)
messages: 139624
nosy: lyricconch
priority: normal
severity: normal
status: open
title: factory func of collections.defaultdict should receive the "missing key" 
as args when called.
type: behavior
versions: Python 2.7

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[issue12635] use "as" for block scope support

[HaiYun Yan]

New submission from HaiYun Yan :

use "as" for block scope support
just like mozilla javascript "let" extension
https://developer.mozilla.org/en/new_in_javascript_1.7#Block_scope_with_let_%28Merge_into_let_Statement%29

usage:

as_clause(as_declare): "as" NAME
as_stmt: NAME "as" test
as_expr: "(" expr "as" NAME ")" expr

var declare by as_clause is alive in  only
eg:
with open(...) as f:
   ...


the same rule to "except E as e: "

spec:
from socket import AF_INET as IPv4

IPv4 = None
assert socket.AF_INET == None

var in as_stmt is alive in current indentation
eg:
for i in range(10):
   
   t as f()+1 
   ...
   

var in as_expr is alive in sub expr only
eg:
t = None
x = (2+3 as t) t**2
assert t == None ane  x == 25

Suggestion:
new opcode
ENTER_BLOCK #depth #varslots

--
components: Interpreter Core
messages: 141076
nosy: lyricconch
priority: normal
severity: normal
status: open
title: use "as" for block scope support
type: feature request

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