title: unordered_map<int, vector<float>> equivalent in Python
body: <p>I need a structure in Python which maps an integer index to a vector of floating point numbers. My data is like:</p>
  
  <pre><code>[0] = {1.0, 1.0, 1.0, 1.0}
  [1] = {0.5, 1.0}
  </code></pre>
  
  <p>If I were to write this in C++ I would use the following code for define / add / access as follows:</p>
  
  <pre><code>std::unordered_map&lt;int, std::vector&lt;float&gt;&gt; VertexWeights;
  VertexWeights[0].push_back(0.0f);
  vertexWeights[0].push_back(1.0f);
  vertexWeights[13].push_back(0.5f);
  std::cout &lt;&lt;vertexWeights[0][0];
  </code></pre>
  
  <p>What is the equivalent structure of this in Python? </p>