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Programming-Idioms

  • VB
  • Erlang
  • Python

Idiom #329 Read value in a map

Assign to v the value stored in the map m for the key k.

Explain what happens if there is no entry for k in m.

v = m[k]

The KeyError exception is raised if the key k doesn't exist in the dict m.
v = m.get(k, "default value")

The second argument is returned if there is no key k in the dict m.
v = m.get(k)

This returns None if there is no key k in the dict m.
var v = m[k];

If no entry, throw an exception; use TryGetValue or GetValueOrDefault instead.
New implementation...
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programming-idioms.org 
v = m[k]
v = m.get(k, "default value")
v = m.get(k)
var v = m[k];
v, ok := m[k]
v := m[k]
v = m.get(k);
v = m.get(k);
m.getOrDefault(k, null);
local v=m[k]
Type
  TMap = specialize TFPGMap<TKey, TData>;

var
  m: TMap;

...
  if not m.TryGetData(k,v) then ;
$v = $m{$k} // 'foobar';
$v = $m{$k};
v = m[k]