title: python assignment fails in else part of conditional operation
body: <p>Why assignment fails at else part ? I was trying to increment two variables based on a condition in below one line .</p>
  
  <pre><code>&gt;&gt;&gt; a=0
  &gt;&gt;&gt; b=0
  &gt;&gt;&gt; a+=1 if True else b
  &gt;&gt;&gt; a
  &gt;&gt;&gt; 1
  &gt;&gt;&gt; a if True else b+=1
    File "&lt;input&gt;", line 1
  SyntaxError: can't assign to conditional expression
  &gt;&gt;&gt; a if False else b+=1
    File "&lt;input&gt;", line 1
  SyntaxError: can't assign to conditional expression
  &gt;&gt;&gt; a+=1 if False else b
  &gt;&gt;&gt; a
  &gt;&gt;&gt; 1
  &gt;&gt;&gt; a+=1 if True else b+=1
    File "&lt;input&gt;", line 1
      a+=1 if True else b+=1
                          ^
  SyntaxError: invalid syntax
  </code></pre>