python学习心得

python中的append学习心得

append只是在恰当的位置修改原来的列表。这意味着，他不是返回一个修改过的列表，而是直接修改原来的列表。比如下面的例子：

result = []
for x in range(3):
    for y in range(3):
        print(result.append((x,y)))

这段代码会返回9个one,对上面进行如下修改：

result = []
for x in range(3):
    for y in range(3):
        result.append((x,y))
        print(result)
结果如下：
 RESTART: C:/Users/Administrator/AppData/Local/Programs/Python/Python37/代码/21.py 
[(0, 0)]
[(0, 0), (0, 1)]
[(0, 0), (0, 1), (0, 2)]
[(0, 0), (0, 1), (0, 2), (1, 0)]
[(0, 0), (0, 1), (0, 2), (1, 0), (1, 1)]
[(0, 0), (0, 1), (0, 2), (1, 0), (1, 1), (1, 2)]
[(0, 0), (0, 1), (0, 2), (1, 0), (1, 1), (1, 2), (2, 0)]
[(0, 0), (0, 1), (0, 2), (1, 0), (1, 1), (1, 2), (2, 0), (2, 1)]
[(0, 0), (0, 1), (0, 2), (1, 0), (1, 1), (1, 2), (2, 0), (2, 1), (2, 2)]
>>> 

如果只想要最后一行，可以对代码再进行修改：

result = []
for x in range(3):
    for y in range(3):
        result.append((x,y))
print(result)
 结果如下：
 RESTART: C:/Users/Administrator/AppData/Local/Programs/Python/Python37/代码/21.py 
[(0, 0), (0, 1), (0, 2), (1, 0), (1, 1), (1, 2), (2, 0), (2, 1), (2, 2)]