Python 递归问卷验证

Question

我在 Python 中创建了一个 function 来查看字典中的一系列问题，并根据问卷的答案从数据集中删除记录。 我创建了调查问卷，因此用户只能回答yes或no 。 我有第三个分支来处理用户响应不是yes或no的情况，但我希望 function 重复现有问题。 目前，它返回并从第一个问题重新开始。 我可以添加什么来修复此功能？

作为参考，这是我创建的 function：

def questionnaire(df, questions = questions):
    for i in range(0, len(questions)): #len(questions)-1):
        print(list(questions.keys())[i])
        
        ans = str(input())
        if ans.lower() == 'yes':
            if list(questions.values())[i][1] == "Yes":
                df = df[df.Section.isin(list(questions.values())[i][0]) == False]
        elif ans.lower() == 'no':
            if list(questions.values())[i][1] == "No":
                df = df[df.Section.isin(list(questions.values())[i][0]) == False]
        else:
            print("Please type yes or no.")
            questionnaire(df, questions = questions)
        
    return df

Answer 1

这应该适用于您的问题：

def questionnaire(df, questions=questions):
    for i in range(0, len(questions)):  #len(questions)-1):
        print(list(questions.keys())[i])
        ans = None
        while ans not in ['yes', 'no']:
            print("Please type yes or no.")
            ans = str(input()).lower()
        if ans == 'yes':
            if list(questions.values())[i][1] == "Yes":
                df = df[df.Section.isin(list(questions.values())[i][0]) ==
                        False]
        else:
            if list(questions.values())[i][1] == "No":
                df = df[df.Section.isin(list(questions.values())[i][0]) ==
                        False]
    return df

因此，您可以将其转换为以下代码：

def questionnaire(df, questions=questions):
    for i in range(0, len(questions)):  #len(questions)-1):
        print(list(questions.keys())[i])
        ans = None
        while ans not in ['yes', 'no']:
            print("Please type yes or no.")
            ans = str(input()).lower()
        question = list(questions.values())[i]
        if question[1] == ans.title():
            df = df[df.Section.isin(question[0]) == False]
    return df

Answer 2

问题：递归，再次重新启动整个问卷

您在问题循环中有太多行，您可能看不到递归：

def questionnaire(df, questions = questions):
    for i in range(0, len(questions)): #len(questions)-1):
        # your code omitted for clarity
        else:
            print("Please type yes or no.")
            questionnaire(df, questions = questions)  # RECURSION! Starting the questionnaire over again

让我们先通过一些重构来清理场景。 然后我们可以尝试解决问题。 我们需要一个循环来代替递归。

重构：提取函数以使循环短而干净

首先让我们添加一些注释来解释抽象（您的代码打算做什么）：

def questionnaire(df, questions = questions):
    # ask all questions, one at a time
    for i in range(0, len(questions)):  # for each question
        print(list(questions.keys())[i])  # ask current question
        
        ans = str(input())  # get user input as answer
        if ans.lower() == 'yes':
            # verify if given answer (title-cased YES) was expected
            if list(questions.values())[i][1] == "Yes":
                df = df[df.Section.isin(list(questions.values())[i][0]) == False]
        elif ans.lower() == 'no':
            # verify if given answer (title-cased NO) was expected
            if list(questions.values())[i][1] == "No":
                df = df[df.Section.isin(list(questions.values())[i][0]) == False]
        else:
            # if given answer is invalid (not in set of expected answers), ask again 
            print("Please type yes or no.")
            questionnaire(df, questions = questions)
        
    return df

使用评论我们可以看到相似之处并重构它。 还进行了一些改进：

• 假设questions是映射到值answer_options的关键question的 Python 字典。 除了使用 for-i 进行迭代然后建立索引之外，您还可以使用 for-each for question, answer_tuple in questions_dict.items()然后将list(questions.keys())[i]替换为question和list(questions.values())[i]到answer_tuple 。
• 而是print(question); ans = input() print(question); ans = input()可以直接提示input(question)

def ask(question):
   # ask current question
   return str(input(question))  # get user input as answer


def store_answer(df, expected)
    return df[df.Section.isin(expected) == False]


def collect_answer(df, question, answer_tuple):
        ans = ask(question)
        while ans.lower() not in  {'yes', 'no'}:
            print("Invalid answer. Please type either yes or no.")
            ans = ask(question)

        # valid answer to store
        if ans.title() == answer_tuple[1]:  # if correct answer given
            return store_answer(df, answer_tuple[0])
        return df

def questionnaire(df, questions_dict = questions):
    # ask all questions, one at a time
    for question, answer_tuple in questions_dict.items():  # for each dict entry (question with answer_tuple)
        df = collect_answer(df, question, answer_tuple)
    return df

由模式固定：循环直到有效输入

我们只是在循环中再次询问当前问题，而不是使用questionnaire(df, questions)的递归，直到给出有效输入：

    ans = ask(question)
    while ans.lower() not in {'yes', 'no'}:
        print("Invalid answer. Please type either yes or no.")
        ans = ask(question)
    # valid answer to store

如果没有给出有效答案，那么它只会再次询问当前问题......只要答案不在有效选项集中{'yes', 'no'} 。 一旦这个while循环退出，我们就知道答案是有效的并且可以继续。