擅长:python、mysql、java
<p>列表理解是python中用于生成列表的压缩语法。如果你重写这个,它可能会非常清楚</p>
<p>一般语法是:<code>[expression for element in list (optional: if condition)]</code>,它返回一个列表</p>
<p>这与写作完全相同:</p>
<pre><code>new_list = []
for element in original_list:
if (condition):
new_list.append(expression)
</code></pre>
<p>在您的例子中,您可以重写两个列表理解(它们是嵌套的),如下所示:</p>
<p>arr=<code>[[second comprehension] for r in range(n_rows)]</code>-></p>
<pre><code>arr = []
for r in range(n_rows):
arr.append(second list)
</code></pre>
<p>现在,对于第二个列表:</p>
<pre><code>second_list = []
for c in range(n_cols):
entry = int(input("Enter value for {}. row and {}. column: ".format(r + 1, c + 1)))
second_list.append(entry)
</code></pre>
<p>整个流程是:</p>
<pre><code>arr = []
for r in range(n_rows):
second_list = []
for c in range(n_cols):
entry = int(input("Enter value for {}. row and {}. column: ".format(r + 1, c + 1)))
second_list.append(entry)
arr.append(second list)
</code></pre>