带有列表的python嵌套循环

Question

好的，所以我正在解决几个问题，并且不知道如何启动这个问题。 我不太清楚如何执行嵌套循环，因此我们给出了一个创建笑脸的列表，然后提供了此说明。

smiley = [[" ","#"," ","#"," "],
      [" ","#"," ","#"," "],
      [" ","#"," ","#"," "],
      [" "," "," "," "," "],
      ["#"," "," "," ","#"],
      [" ","#"," ","#"," "],
      [" ","#","#","#"," "],
      [" "," "," "," "," "]]

根据上面定义的笑脸创建一个新的局部变量。 更严格地说，您对此新变量的定义需要显式使用变量笑脸。 使用嵌套的for循环可更改存储在新创建的局部变量中的字符。 不要从任何列表中添加或删除任何元素。 仅更改/替换。 但是，您可以使用任何其他单个字符更改和替换任何字符。 返回此本地列表列表。

所以我该如何为这些列表嵌套循环并更改其项目而不更改其他所有项目？

我只有这个，但我不认为这应该是我的起点，请帮助我

def moodSwing():
face = smiley.copy()
for each in face[:1]:
    for each in face[1:2]:

Answer 1

尝试以下操作在所需行号和字符号的"#"和" "之间切换：

def moodSwing(smiley, coords):
    face = list(smiley)
    for row, character in coords:
        for r in range(len(face)):
            for c in range(r):
                if r == row+1 and c == character+1:
                    if face[r][c] == " ":
                        face[r][c] = "#"
                    else:
                        face[r][c] = " "
    return face

然后执行以下操作：

>>> frown = moodSwing(smiley, [(4, 0), (4, 4), (5, 1), (5, 2), (5, 3), (6, 1), (6, 2), (6, 3)])

Answer 2

for list_index, lst in enumerate(face):
    for item_index, item in enumerate(lst):
        if item == '#':
            face[list_index][item_index] = ' '
        else:
            face[list_index][item_index] = '#'  

上面的代码翻转字符。 item是当前列表中的元素。
使用索引来更改元素。