Is there method like python popitem for associative arrays in dlang?

Question

I want to get any key/value pair from associative array and remove it. In python it's:

key, value = assoc.popitem()

In D I do:

auto key = assoc.byKey.front;
auto value = assoc[key];
assoc.remove(key);

Is there better way to do this? Is it possible to use byKeyValue() outside foreach?

DMD 2.067.1

Answer 1

Is it possible to use byKeyValue() outside foreach?

Sure:

import std.stdio;

void main()
{
    int[string] assoc = ["apples" : 2, "bananas" : 4];

    while (!assoc.byKeyValue.empty)
    {
        auto pair = assoc.byKeyValue.front;
        assoc.remove(pair.key);
        writeln(pair.key, ": ", pair.value);
    }
}

Is there better way to do this?

I don't think D has a library function equivalent for popitem.

Answer 2

Before even thinking about it, I'd point out that you could write a simple function:

import std.typecons;

Tuple!(K, V) popitem(K, V)(ref V[K] arr) { 
    foreach(k, v; arr) { 
        arr.remove(k); 
        return tuple(k, v); 
    } 
    throw new Exception("empty!"); 
} 
void main() { 
    int[string] cool; 
    cool["ten"] = 10; 
    cool["twenty"] = 20; 
    import std.stdio; 
    writeln(cool.popitem()); 
    writeln(cool.popitem()); 
}

Or using byKeyValue:

auto popitem(K, V)(ref V[K] arr) { 
    foreach(item; arr.byKeyValue()) { 
        arr.remove(item.key); 
        return item; 
    } 
    throw new Exception("empty!"); 
} 
void main() { 
    int[string] cool; 
    cool["ten"] = 10; 
    cool["twenty"] = 20; 
    import std.stdio; 
    auto item = cool.popitem(); 
    writeln(item.key, item.value); 
    item = cool.popitem(); 
    writeln(item.key, item.value); 
}   

Generally, I like to encourage people not to be afraid of writing their own functions. If you can express something with a few existing things, just write your own function, give it a name you like, and use that! With the uniform function call syntax, you can easily even write extension methods for built in types, like I did here, and use it as if it has always been there.