This is an old question, but here’s my two cents. PeterSO’s answer is slightly more concise, but slightly less efficient. You already know how big it’s going to be so you don’t even need to use append: keys := make([]int, len(mymap)) i := 0 for k := range mymap { keys[i] = k i++ } … Read more
From Python 3.6 onwards, the standard dict type maintains insertion order by default. Defining d = {‘ac’:33, ‘gw’:20, ‘ap’:102, ‘za’:321, ‘bs’:10} will result in a dictionary with the keys in the order listed in the source code. This was achieved by using a simple array with integers for the sparse hash table, where those integers … Read more
The json module is a good solution here. It has the advantages over pickle that it only produces plain text output, and is cross-platform and cross-version. import json json.dumps(dict)
Update – 2020 Since this question was asked almost ten years ago, quite a bit has changed in Python itself since then. While the approach in my original answer is still valid for some cases, (e.g. legacy projects stuck to older versions of Python and cases where you really need to handle dictionaries with very … Read more
In newer versions of typescript you can use: type Customers = Record<string, Customer> In older versions you can use: var map: { [email: string]: Customer; } = { }; map[‘foo@gmail.com’] = new Customer(); // OK map[14] = new Customer(); // Not OK, 14 is not a string map[‘bar@hotmail.com’] = ‘x’; // Not OK, ‘x’ is … Read more
On a Python version where dicts actually are ordered, you can do my_dict = {‘foo’: ‘bar’, ‘spam’: ‘eggs’} next(iter(my_dict)) # outputs ‘foo’ For dicts to be ordered, you need Python 3.7+, or 3.6+ if you’re okay with relying on the technically-an-implementation-detail ordered nature of dicts on Python 3.6. For earlier Python versions, there is no … Read more
For Python 3+: >>> mydict {‘four’: 4, ‘three’: 3, ‘one’: 1} >>> for k in list(mydict.keys()): … if mydict[k] == 3: … del mydict[k] >>> mydict {‘four’: 4, ‘one’: 1} The other answers work fine with Python 2 but raise a RuntimeError for Python 3: RuntimeError: dictionary changed size during iteration. This happens because mydict.keys() … Read more
Each element of the container is a map<K, V>::value_type, which is a typedef for std::pair<const K, V>. Consequently, in C++17 or higher, you can write for (auto& [key, value]: myMap) { std::cout << key << ” has value ” << value << std::endl; } or as for (const auto& [key, value]: myMap) { std::cout << … Read more
You can achieve this like following : map<string, int>::iterator it; for (it = symbolTable.begin(); it != symbolTable.end(); it++) { std::cout << it->first // string (key) << ‘:’ << it->second // string’s value << std::endl; } With C++11 ( and onwards ), for (auto const& x : symbolTable) { std::cout << x.first // string (key) << … Read more
Here is everything about Python dicts that I was able to put together (probably more than anyone would like to know; but the answer is comprehensive). Python dictionaries are implemented as hash tables. Hash tables must allow for hash collisions i.e. even if two distinct keys have the same hash value, the table’s implementation must … Read more