将变量追加到循环列表中答案

【问题标题】：Trying to append variable to list in loop if it doesn't exist already, but the result is empty将变量追加到循环列表中
【发布时间】：2022-01-10 05:43:00
【问题描述】：

如果数字不在列表中，我想将“输入数字”附加到“list_of_already_entered_numbers”。因此，您不应将相同的数字说出 2 次。我添加了“打印”以显示列表仍然是空的？即使“追加”应该在每次迭代期间将数字添加到列表中。别介意10次迭代。那么如何将数字附加到列表中，以便每次迭代都更新列表？

def ask_number():
    a = 0
    while a < 10:
        list_of_already_entered_numbers = []
        print("this is the list: " + str(list_of_already_entered_numbers))
        number = int(input("Type a number:"))
        if number in list_of_already_entered_numbers:
            print("the number is already in the list")
        else:
            list_of_already_entered_numbers.append(number)
        a+=1

ask_number()

【问题讨论】：

您在循环的每次迭代开始时将list_of_already_entered_numbers 设置为一个空列表。尝试将其设置在 while 循环之外。
每次循环执行时变量list_of_already_entered_numbers 被重新定义为一个空字符串。在循环外定义变量。
@match 打败了我！

标签： python loops if-statement append iteration

【解决方案1】：

像这样在循环外声明列表：

def ask_number():
    a = 0
    list_of_already_entered_numbers = []
    while a < 10:
        print("this is the list: " + str(list_of_already_entered_numbers))
        number = int(input("Type a number:"))
        if number in list_of_already_entered_numbers:
            print("the number is already in the list")
        else:
            list_of_already_entered_numbers.append(number)
        a+=1

ask_number()

【讨论】：

【解决方案2】：

您可以尝试仅将询问部分分解为它自己的函数。这样可以更轻松地自行尝试，并确保您获得预期的结果：

from typing import List

def enter_number(previous_numbers: List[int]) -> List[int]:
    print("These numbers have been guessed: {previous_numbers}" + str(list_of_already_entered_numbers))
    number = int(input("Type a number:"))
    if number in previous_numbers:
        print("That number has already been entered")
    else:
        previous_numbers.append(number)
    return previous_numbers

def ask():
    previous_numbers = []
    for _ in range(10):
        previous_numbers = enter_number(previous_numbers)

ask()

通过这种方式，您可以封装起始状态，并且可以确保每次迭代都按照您的预期进行。

【讨论】：