Update: In Python 2.6 and onwards, consider whether the namedtuple data structure suits your needs: >>> from collections import namedtuple >>> MyStruct = namedtuple(‘MyStruct’, ‘a b d’) >>> s = MyStruct(a=1, b={‘c’: 2}, d=[‘hi’]) >>> s MyStruct(a=1, b={‘c’: 2}, d=[‘hi’]) >>> s.a 1 >>> s.b {‘c’: 2} >>> s.c Traceback (most recent call last): File … Read more
For your needs, use ConcurrentHashMap. It allows concurrent modification of the Map from several threads without the need to block them. Collections.synchronizedMap(map) creates a blocking Map which will degrade performance, albeit ensure consistency (if used properly). Use the second option if you need to ensure data consistency, and each thread needs to have an up-to-date … Read more
default_data[‘item3’] = 3 Easy as py. Another possible solution: default_data.update({‘item3’: 3}) which is nice if you want to insert multiple items at once.
I can’t reproduce this issue in a simple .NET 4.0 console application: static class Program { static void Main(string[] args) { var myDict = new Dictionary<string, string> { { “key1”, “value1” }, { “key2”, “value2” } }; Console.ReadKey(); } } Can you try to reproduce it in a simple Console application and go from there? … Read more
Are dictionaries ordered in Python 3.6+? They are insertion ordered[1]. As of Python 3.6, for the CPython implementation of Python, dictionaries remember the order of items inserted. This is considered an implementation detail in Python 3.6; you need to use OrderedDict if you want insertion ordering that’s guaranteed across other implementations of Python (and other … Read more
You can use dict.get() value = d.get(key) which will return None if key is not in d. You can also provide a different default value that will be returned instead of None: value = d.get(key, “empty”)
Constructing a new dict: dict_you_want = { your_key: old_dict[your_key] for your_key in your_keys } Uses dictionary comprehension. If you use a version which lacks them (ie Python 2.6 and earlier), make it dict((your_key, old_dict[your_key]) for …). It’s the same, though uglier. Note that this, unlike jnnnnn’s version, has stable performance (depends only on number of … Read more
You can use a generator expression: >>> dicts = [ … { “name”: “Tom”, “age”: 10 }, … { “name”: “Mark”, “age”: 5 }, … { “name”: “Pam”, “age”: 7 }, … { “name”: “Dick”, “age”: 12 } … ] >>> next(item for item in dicts if item[“name”] == “Pam”) {‘age’: 7, ‘name’: ‘Pam’} If … Read more
Usually, a Python dictionary throws a KeyError if you try to get an item with a key that is not currently in the dictionary. The defaultdict in contrast will simply create any items that you try to access (provided of course they do not exist yet). To create such a “default” item, it calls the … Read more
Bash 4 Bash 4 natively supports this feature. Make sure your script’s hashbang is #!/usr/bin/env bash or #!/bin/bash so you don’t end up using sh. Make sure you’re either executing your script directly, or execute script with bash script. (Not actually executing a Bash script with Bash does happen, and will be really confusing!) You … Read more