CODEWITHSUNDEEP
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dmeister
dmeister

Reputation: 35654

Equivalent for LinkedHashMap in Python

LinkedHashMap is the Java implementation of a Hashtable like data structure (dict in Python) with predictable iteration order. That means that during a traversal over all keys, they are ordered by insertion. This is done by an additional linked list maintaining the insertion order.

Is there an equivalent to that in Python?

Upvotes: 33

Views: 26522

Answers (5)

Eli Courtwright
Eli Courtwright

Reputation: 193181

As of Python 3.7, dict objects maintain their insertion order by default.

If you're on Python 2.7 or Python >=3.1 you can use collections.OrderedDict in the standard library.

This answer to the question How do you retrieve items from a dictionary in the order that they’re inserted? contains an implementation of an ordered dict, in case you're not using Python 3.x and don't want to give yourself a dependency on the third-party ordereddict module.

Upvotes: 28

Isa Rota
Isa Rota

Reputation: 563

In addition to the validated comment;

As of Python 3.7, dict preserves insertion order.

This answer shows this with details.

Upvotes: 2

sykloid
sykloid

Reputation: 101366

Although you can do the same thing by maintaining a list to keep track of insertion order, Python 2.7 and Python >=3.1 have an OrderedDict class in the collections module.

Before 2.7, you can subclass dict following this recipe.

Upvotes: 12

aatifh
aatifh

Reputation: 2337

I am not sure whether this is what you are asking for:

>>> dic = {1: 'one', 2: 'two'}
>>> for k, v in dic.iteritems():
...     print k, v

you can order the dic in the order of the insertion using ordereddict module.

d = ordereddict(dic, relax=True)

Upvotes: 3

DNS
DNS

Reputation: 38219

I don't think so; you'd have to use a dict plus a list. But you could pretty easily wrap that in a class, and define keys, __getitem__, __setitem__, etc. to make it work the way you want.

Upvotes: 1

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