含有tuple的list按照tuple中的某一位进行排序

tuple构成的list可以按照tuple中的任意一位进行排序。

在python中的例子如下：

[(13, 1), (11, 1), (9, 1), (6, 1), (1, 1), (2, 1), (4, 1), (13, 1), (4, 1), (2, 1), (13, 1), (0, 1), (7, 1), (11, 2), (9, 2), (6, 2), (1, 2), (2, 2), (13, 2), (2, 2), (8, 2), (12, 2), (13, 2), (0, 2), (7, 2), (4, 3), (13, 3), (5, 3), (5, 3), (4, 3), (6, 3)]

要将上面的list按照tuple中的第一位升序排列：

[(0, 1), (0, 2), (1, 1), (1, 2), (2, 1), (2, 1), (2, 2), (2, 2), (4, 1), (4, 1), (4, 3), (4, 3), (5, 3), (5, 3), (6, 1), (6, 2), (6, 3), (7, 1), (7, 2), (8, 2), (9, 1), (9, 2), (11, 1), (11, 2), (12, 2), (13, 1), (13, 1), (13, 1), (13, 2), (13, 2), (13, 3)]

python中的方法是调用sorted函数，sorted函数可以指定key，用lambda关键字定义“单行最小函数”。单行最小函数是说在一行代码中定义函数，可以看作是内联函数。

例子：

<tt class="prompt">>>> </tt><span class="userinput"><span class="pykeyword" style="color:navy;background-color:white; font-weight:bold;">def</span><span class="pyclass" style="color:blue;background-color:white; font-weight:bold;"> f</span>(x):</span>
<tt class="prompt">...     </tt><span class="userinput"><span class="pykeyword" style="color:navy;background-color:white; font-weight:bold;">return</span> x*2</span>
<tt class="prompt">...     </tt><span class="userinput"></span>
<tt class="prompt">>>> </tt><span class="userinput">f(3)</span>
<span class="computeroutput" style="color:teal;background-color:white;">6</span>
<tt class="prompt">>>> </tt><span class="userinput">g = <span class="pykeyword" style="color:navy;background-color:white; font-weight:bold;">lambda</span> x: x*2</span>
<tt class="prompt">>>> </tt><span class="userinput">g(3)</span>
<span class="computeroutput" style="color:teal;background-color:white;">6</span>
<tt class="prompt">>>> </tt><span class="userinput"><span class="pykeyword" style="color:navy;background-color:white; font-weight:bold;">(lambda</span> x: x*2)(3)</span>
<span class="computeroutput" style="color:teal;background-color:white;">6</span>

l=[(1,2),(2,5),(3,6),(2,7),(2,8)]
sorted_l=sorted(l,key=lambda t:t[0])
print(sorted_l)
sorted_l=sorted(l,key=lambda t:t[1])
print(sorted_l)

得到的结果是：

[(1, 2), (2, 5), (2, 7), (2, 8), (3, 6)] #按照tuple的第一位排序

[(1, 2), (2, 5), (3, 6), (2, 7), (2, 8)] #按照tuple的第二位排序