title: Why is it valid to assign to an empty list but not to an empty tuple?
body: <p>This came up in <a href="https://youtu.be/MCs5OvhV9S4?t=42m17s" rel="noreferrer">a recent PyCon talk</a>.</p>
  
  <p>The statement</p>
  
  <pre><code>[] = []
  </code></pre>
  
  <p>does nothing meaningful, but it does not throw an exception either. I have the feeling this must be due to unpacking rules. You can do <a href="http://openbookproject.net/thinkcs/python/english3e/tuples.html#tuple-assignment" rel="noreferrer">tuple unpacking</a> with lists too, e.g.,</p>
  
  <pre><code>[a, b] = [1, 2]
  </code></pre>
  
  <p>does what you would expect. As logical consequence, this also should work, when the number of elements to unpack is 0, which would explain why assigning to an empty list is valid. This theory is further supported by what happens when you try to assign a non-empty list to an empty list:</p>
  
  <pre><code>&gt;&gt;&gt; [] = [1]
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
  ValueError: too many values to unpack
  </code></pre>
  
  <p>I would be happy with this explanation, if the same would also be true for tuples. If we can unpack to a list with 0 elements, we should also be able to unpack to a tuple with 0 elements, no? However:</p>
  
  <pre><code>&gt;&gt;&gt; () = ()
    File "&lt;stdin&gt;", line 1
  SyntaxError: can't assign to ()
  </code></pre>
  
  <p>It seems like unpacking rules are not applied for tuples as they are for lists. I cannot think of any explanation for this inconsistency. Is there a reason for this behavior? </p>