Pre-PEP: Dictionary accumulator methods
El Pitonero
pitonero at gmail.com
Sat Mar 19 05:24:24 EST 2005
On Sat, 19 Mar 2005 01:24:57 GMT, "Raymond Hettinger"
<vze4rx4y at verizon.net> wrote:
>I would like to get everyone's thoughts on two new dictionary methods:
>
> def count(self, value, qty=1):
> try:
> self[key] += qty
> except KeyError:
> self[key] = qty
>
> def appendlist(self, key, *values):
> try:
> self[key].extend(values)
> except KeyError:
> self[key] = list(values)
Bengt Richter wrote:
> >>> class xdict(dict):
> ... def valadd(self, key, incr=1):
> ... try: self[key] = self[key] + type(self[key])(incr)
> ... except KeyError: self[key] = incr
What about:
import copy
class safedict(dict):
def __init__(self, default=None):
self.default = default
def __getitem__(self, key):
try:
return dict.__getitem__(self, key)
except KeyError:
return copy.copy(self.default)
x = safedict(0)
x[3] += 1
y = safedict([])
y[5] += range(3)
print x, y
print x[123], y[234]
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