dict get item from key-CodePudding

I'm trying to get a key-value item from a dictionary using a key instead of getting only the value. I understand that I could do something like

foo = {"bar":"baz", "hello":"world"}
some_item = {"bar": foo.get("bar")}

But here I need to type out the key twice, which seems a bit redundant. Is there some direct way to get the key-value pair for the key bar? Something like

foo.get_item("bar")
>>> {"bar": "baz"}

CodePudding user response：

One way or another, you'll need to bind "bar" to a variable.

>>> foo = {"bar":"baz", "hello":"world"}
>>> (lambda k="bar": {k: foo[k]})()
{'bar': 'baz'}

or:

>>> k = "bar"
>>> {k: foo[k]}
{'bar': 'baz'}

or:

>>> def item(d, k):
...     return {k: d[k]}
...
>>> item(foo, "bar")
{'bar': 'baz'}

CodePudding user response：

It's possible to extend dict to create your own methods. It could be useful if you're the one creating the initial dictionary in the first place.

class MyDict(dict):
    def fetch(self, key):
        return {key:self.get(key)}

The downside is you would need to recast regular dictionaries (assuming you didn't create the initial)

new_foo = MyDict(foo)
some_item = new_foo.fetch("bar")

But in this case it would probably be easier just to use a lambda (see Samwise's answer)

CodePudding user response：

you can get the key value pair for key 'bar' by doing something like ->

foo = {"bar":"baz", "hello":"world"}
some_item = {k:v for k,v in foo.items() if k=='bar'}