Greetings,
I'm trying to categorize items in a list, by copying them into a
dictionary...
A simple example with strings doesn't seem to work how I'd expect:
>>> basket = ['apple', 'orange', 'apple', 'pear', 'orange', 'banana']
>>> d = {}
>>> d = d.fromkeys(basket, [])
>>> d
{'orange': [], 'pear': [], 'apple': [], 'banana': []}
>>> for fruit in basket:
... d[fruit].append(fruit)
...
No if I print d I'd EXPECT....
>>> d
{'orange': ['orange', 'orange'], 'pear': ['pear'], 'apple': ['apple',
'apple'], 'banana': ['banana']}
But what I GET is....
>>> d
{'orange': ['apple', 'orange', 'apple', 'pear', 'orange', 'banana'], 'pear':
['apple', 'orange', 'apple', 'pear', 'orange', 'banana'], 'apple': ['apple',
'orange', 'apple', 'pear', 'orange', 'banana'], 'banana': ['apple',
'orange', 'apple', 'pear', 'orange', 'banana']}
>>>
>From what I can work out, there is only ONE list that is referenced from the
dictionary 4 times. Which would be because the *same empty list* is assigned
to every key in the dictionary by the "fromkeys" line. But that seems
*seriously
*counter-intuitive to me...
Would anyone beg to differ and try to rewire my thinking? (I'm from a Java
background if that helps)
I've already solved the problem a different way, but I am concerned about
this counter-intuitiveness as I see it.
rgds,
Daniel Jowett
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