New subject: [Python-Dev] What if replacing items in a dictionary returns the new dictionary?

May 5, 2011

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2011/4/29 Roy Hyunjin Han <starsareblueandfaraway@gmail.com>:
It would be convenient if replacing items in a dictionary returns the
new dictionary, in a manner analogous to str.replace().  What do you
think?
# Current behavior
   x = {'key1': 1}
   x.update(key1=3) == None
   x == {'key1': 3} # Original variable has changed
# Possible behavior
   x = {'key1': 1}
   x.replace(key1=3) == {'key1': 3}
   x == {'key1': 1} # Original variable is unchanged
2011/5/5 Giuseppe Ottaviano <giuott@gmail.com>:
In general nothing stops you to use a proxy object that returns itself
after each method call, something like
class using(object):
   def __init__(self, obj):
       self._wrappee = obj
def unwrap(self):
       return self._wrappee
def __getattr__(self, attr):
       def wrapper(*args, **kwargs):
           getattr(self._wrappee, attr)(*args, **kwargs)
           return self
       return wrapper
d = dict()
print using(d).update(dict(a=1)).update(dict(b=2)).unwrap()
# prints {'a': 1, 'b': 2}
l = list()
print using(l).append(1).append(2).unwrap()
# prints [1, 2]
Cool!  I never thought of that.  That's a great snippet.

I'll forward this to the python-ideas list.  I don't think the
python-dev people want this discussion to continue on their mailing
list.

Re: [Python-ideas] [Python-Dev] What if replacing items in a dictionary returns the new dictionary?

Roy Hyunjin Han

Roy Hyunjin Han

Roy Hyunjin Han

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