append（）方法

作用：append() 方法用於在列表末尾新增新的物件。該方法無返回值，但是會修改原來的列表。

場景:該方法可以用於在迴圈迭代過程中儲存每一次的執行結果，比如為了畫圖，儲存邏輯迴歸過程中每一次迭代的代價函式結果值。

#定義空列表
costs = []

for i in range(10):
    #在代價函式2列表末尾新增新的值
    costs.append(i)
    #顯示每次新增新物件後的列表
    print("costs = " + str(costs))

costs = [0]
costs = [0, 1]
costs = [0, 1, 2]
costs = [0, 1, 2, 3]
costs = [0, 1, 2, 3, 4]
costs = [0, 1, 2, 3, 4, 5]
costs = [0, 1, 2, 3, 4, 5, 6]
costs = [0, 1, 2, 3, 4, 5, 6, 7]
costs = [0, 1, 2, 3, 4, 5, 6, 7, 8]
costs = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]