擅长:python、mysql、java
<p>来自<a href="http://docs.python.org/reference/expressions.html#index-917" rel="nofollow noreferrer">the docs</a>:</p>
<blockquote>
<p>There is ambiguity in the formal
syntax here: anything that looks like
an expression list also looks like a
slice list, so any subscription can be
interpreted as a slicing. Rather than
further complicating the syntax, this
is disambiguated by defining that in
this case the interpretation as a
subscription takes priority over the
interpretation as a slicing (this is
the case if the slice list contains no
proper slice nor ellipses). Similarly,
when the slice list has exactly one
short slice and no trailing comma, the
interpretation as a simple slicing
takes priority over that as an
extended slicing.</p>
</blockquote>
<p>因此,我认为不可能区分<code>u[1,2]</code>-作为扩展切片与{<cd1>}-作为元组键。在</p>