Python dicts are now ordered
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Python dicts are now ordered
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Re: Python dicts are now ordered
#2"Ordered dict" is ambiguous, and from the title I thought that key order was meant. Reading the article, I see that it's actually insertion order. Which makes much more sense. Key order would have been a much more significant change.
Re: Python dicts are now ordered
#3Javascript taught me to never assume any ordering in a dict/map/hashmap (whatever the term)
Re: Python dicts are now ordered
#4Javascript taught me to never assume any ordering in a dict/map/hashmap (whatever the term)
Is the ordering there at least fixed, or can it vary from run to run even on the same data, or between implementations or versions of the same implementation?
EDIT: to clarify, I was asking about JavaScript there.
Re: Python dicts are now ordered
#5Brandon Rhodes gave a great talk at PyCon 2017 about the evolution of dictionaries in Python.
I really appreciate the people who dive deep into these implementation details, and continue to optimize the languages we all use.
Re: Python dicts are now ordered
#6Javascript taught me to never assume any ordering in a dict/map/hashmap (whatever the term)
Is the ordering there at least fixed, or can it vary from run to run even on the same data, or between implementations or versions of the same implementation? EDIT: to clarify, I was asking about JavaScript there.
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Re: Python dicts are now ordered
#7Javascript taught me to never assume any ordering in a dict/map/hashmap (whatever the term)
Well, JavaScript Map preserves insertion order when iterating entries, and as of ES2015 (i.e. ES6), for-in also iterates
the (string, non-numeric) properties of an object in insertion order.
Re: Python dicts are now ordered
#8Javascript taught me to never assume any ordering in a dict/map/hashmap (whatever the term)
That's fine, as long as you adjust your assumptions when working with other languages.
Re: Python dicts are now ordered
#9Javascript taught me to never assume any ordering in a dict/map/hashmap (whatever the term)
Is the ordering there at least fixed, or can it vary from run to run even on the same data, or between implementations or versions of the same implementation? EDIT: to clarify, I was asking about JavaScript there.
It is deterministic, but it's an odd rule-set. For example:
`var o = { 3: 'foo', 1: 'bar', b: 'baz', a: 'quux' }` Will yield:
`{1: "bar", 3: "foo", b: "baz", a: "quux"}`.
Numeric keys get sorted. String keys are insertion-order. If key order is a priority, a Map should be used instead. Often when JavaScript's objects are used and a particular sort order is required, an accompanying (sorted) array is used.
Re: Python dicts are now ordered
#10This is a solid argument for why you should have more datatypes available to you. If your program relies on an insertion order, say so. If anyone ever moves to another implementation, they will thank you for it.