ordereddictionary - Python OrderedDict iteration -


why python ordereddict initialized 'out of order'?

the solution here less intriguing explanation. there's here don't get, , perhaps expanation others me.

>>> collections import ordereddict  >>> spam = ordereddict(s = (1, 2), p = (3, 4), = (5, 6), m = (7, 8))  >>> spam ordereddict([('a', (5, 6)), ('p', (3, 4)), ('s', (1, 2)), ('m', (7, 8))])  >>> key in spam.keys(): ...    print key     ... #  'ordered' not order wanted.... p s m  # expecting (and wanting): s p m

from the docs:

the ordereddict constructor , update() method both accept keyword arguments, order lost because python’s function call semantics pass-in keyword arguments using regular unordered dictionary.

so initialization loses ordering, because it's calling constructor **kwargs.

edit: in terms of solution (not explanation)—as pointed out in comment op, passing in single list of tuples will work:

>>> collections import ordereddict >>> spam = ordereddict([('s',(1,2)),('p',(3,4)),('a',(5,6)),('m',(7,8))]) >>> key in spam: ...     print(key) ... s p m >>> key in spam.keys(): ...     print(key) ... s p m

this because it's getting single argument, list.


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