在for循环中将列表附加到新列表[重复]

Question

我目前正在 python 中试验列表，并试图创建一个程序来模拟名称游戏(click here for refrence)。

程序要求用户输入并生成一个包含用户名每个字母的列表。但是，它必须生成 3 个新名称，每个名称都以“b”、“f”、“m”开头。这是我遇到问题的地方。附加到 master_list 并稍后打印我的结果时，我得到了输出：

[['m', 'o', 'b', 'e', 'r', 't'], ['m', 'o', 'b', 'e', 'r', 't'], 
['m', 'o', 'b', 'e', 'r', 't']]

当用户输入 =“罗伯特”时

这是我的代码：

# Asks for user name
user_name = input("Enter name here: ")
name = list(user_name)

# Create an empty list that will contain a subsets of lists.
master_list = []

# List containing the first letter of each new name
beginning_of_word = ["b", "f", "m"]

# Creates 3 new names and appends them to master_list
for var in beginning_of_word:
    new_list = name
    new_list.pop(0)
    new_list.insert(0, var)
    print(new_list)
    master_list.append(new_list)
    if new_list != name:
        new_list = name

打印 master_list 时的预期输出应该是：

[['b', 'o', 'b', 'e', 'r', 't'], ['f', 'o', 'b', 'e', 'r', 't'], 
['m', 'o', 'b', 'e', 'r', 't']]

有人知道为什么会这样吗？

Answer 1

虽然您将变量命名为new_list，但事实上您每次都在同一个旧列表上进行操作。要修改列表并保留原始列表，您需要复制列表：

# Asks for user name
user_name = input("Enter name here: ")
name = list(user_name)

# Create an empty list that will contain a subsets of lists.
master_list = []

# List containing the first letter of each new name
beginning_of_word = ["b", "f", "m"]

# Creates 3 new names and appends them to master_list
for var in beginning_of_word:
    new_list = list(name)  # a copy of 'name'
    new_list[0] = var
    master_list.append(new_list)

print(master_list)

输出

% python3 test.py
Enter name here: Robert
[['b', 'o', 'b', 'e', 'r', 't'], ['f', 'o', 'b', 'e', 'r', 't'], ['m', 'o', 'b', 'e', 'r', 't']]
%