04-python第四天学习

Posted 2020-10-26 每天进步一点点

（1）for循环里的else

In [1]: nums = [11,22,33,44]

In [2]: for temp in nums:
   ...:     print(temp)
   ...: else:　　　　#else表示当循环打印完才会打印else里的内容
   ...:     print("========")
   ...:     
11
22
33
44
========

（2）列表append的注意点

In [3]: a = [11,22,33]

In [4]: b = [44,55]

In [5]: a.append(b)

In [6]: a
Out[6]: [11, 22, 33, [44, 55]]　　#append相当于把b列表这个整体都放在a列表

In [1]: a = [11,22,33]

In [2]: b = [44,55]

In [3]: a.append(b)

In [4]: a
Out[4]: [11, 22, 33, [44, 55]]

In [5]: a = a.append(b)　　#当执行a.append(b)时，代表已经把b添加到a里面去了，结果已经发生了变化，但是a.append(b)并没有结果输入，则会返回空

In [6]: a