擅长:python、mysql、java
<p>在下面的循环中可以看到正在发生的事情的简化版本:</p>
<pre><code>for i in range(2):
r = []
print(f'r == {r} before append in iteration {i+1}')
r.append(i)
print(f'r == {r} after iteration {i+1}')
# OUTPUT
# r == [] before append in iteration 1
# r == [0] after append in iteration 1
# r == [] before append in iteration 2
# r == [1] after append in iteration 2
</code></pre>
<p>不是<code>r</code>以<code>[0, 1]</code>结束,而是以<code>[1]</code>结束,因为您可以看到,在第一次迭代之后,您将<code>r</code>重置为空列表<code>[]</code>,然后再附加<code>i</code>的下一个值。你知道吗</p>