Python：函数总是从循环中返回零

Question

我正在编写一个函数来查看用户的输入是否在列表中，如果是，则用户输入被删除，并要求他们再次猜测，直到他们退出。

我想计算正确猜测的数量并在调用函数后打印它，出于某种原因，无论正确猜测的数量如何，它都会打印为零。我做错了什么？ （代码和示例如下）

# [ ] Complete Foot Bones Quiz
foot_bones = ["calcaneus", "talus", "cuboid", "navicular", "lateral cuneiform","intermediate cuneiform", "medial cuneiform"]
guess =''
already_guessed = []

def foot_bone_quiz(guess, foot_bones):

    correct_guess = 0

    while True:

        guess = input("Guess a foot bone, enter q to quit. ")


        if guess.lower() in already_guessed:
            print("You already guessed that!")


        elif guess != 'q':

            for bone in foot_bones:

                if bone.lower() == guess.lower():
                    correct_guess = correct_guess + 1
                    print("Yes", guess, "is a bone in the foot!")
                    already_guessed.append(guess.lower())
                    foot_bones.remove(guess.lower())


                else:
                    pass


        elif guess == 'q':
            print('finished')
            break

        else:
            print("Invalid Entry")


    return already_guessed, correct_guess            

foot_bone_quiz(guess, foot_bones)
print("You had", correct_guess, "correct guesses. You guessed: ", already_guessed)

示例输出：

Guess a foot bone, enter q to quit. navicular

Yes navicular is a bone in the foot!

Guess a foot bone, enter q to quit. talus

Yes talus is a bone in the foot!

Guess a foot bone, enter q to quit. q
finished

You had 0 correct guesses. You guessed:  ['navicular', 'talus']

Answer 1

您似乎没有保存从方法 foot_bone_quiz 返回的 correct_guess。

尝试以下方法：

already_guessed, correct_guess = foot_bone_quiz(guess, foot_bones)
print("You had", correct_guess, "correct guesses. You guessed: ", already_guessed)

already_guessed 打印正确，因为它是在 foot_bone_quiz 方法之外初始化的。

Answer 2

在实际运行您的代码时，我得到了这个输出

Guess a foot bone, enter q to quit. navicular
Yes navicular is a bone in the foot!
Guess a foot bone, enter q to quit. talus
Yes talus is a bone in the foot!
Guess a foot bone, enter q to quit. q
finished
Traceback (most recent call last):
  File "F:\Documents\Python\stack.py", line 45, in <module>
    print("You had", correct_guess, "correct guesses. You guessed: ", already_guessed)
NameError: name 'correct_guess' is not defined

正如预期的那样，名称correct_guess 从未在foot_bone_quiz 函数范围之外定义。看来您可能不熟悉 variable scope in python 以及返回值的工作原理

您的测验函数返回 2 个值，但在最后一行的第 2 行调用该函数时，您从不使用这些返回值。此外，already_guessed 变量无论如何都是在函数之外定义的，因此返回它有点多余。最后，您的测验函数采用的 guess 参数是完全多余的，因为您在读取最初传递的内容之前将其值重新分配给输入。

以下是对您的程序的一些建议更改：

• 从程序顶部删除 already_guessed = 和 guess = 分配。
• 从您的测验函数中删除 guess 参数
• 将already_guessed = []赋值放在最开始的测验函数中
• 在最后调用测验方法时，将结果值分配给变量，然后在打印中使用 (already_guessed, correct_guess = foot_bone_quiz(foot_bones))。请注意，guess 参数已如前所述被删除

这是我在这些更改后得到的输出

Guess a foot bone, enter q to quit. navicular
Yes navicular is a bone in the foot!
Guess a foot bone, enter q to quit. talus
Yes talus is a bone in the foot!
Guess a foot bone, enter q to quit. q
finished
You had 2 correct guesses. You guessed:  ['navicular', 'talus']

Answer 3

foot_bones = ["calcaneus", "talus", "cuboid", "navicular", "lateral cuneiform",
          "intermediate cuneiform", "medial cuneiform"]
correct_guess = 0
already_guessed = []


def foot_bone_quiz(foot_bones1):
    global correct_guess
    global already_guessed
    already_guessed = []
    correct_guess = 0
    while True:
        guess1 = input("Guess a foot bone, enter q to quit. ")
        if guess1.lower() in already_guessed:
            print("You already guessed that!")
        elif guess1 != 'q':
            for bone in foot_bones1:
                if bone.lower() == guess1.lower():
                    correct_guess += 1
                    print("Yes", guess1, "is a bone in the foot!")
                    already_guessed.append(guess1.lower())
                    foot_bones1.remove(guess1.lower())

                else:
                    pass
        elif guess1 == 'q':
            print('finished')
            break

        else:
            print("Invalid Entry")
    return already_guessed, correct_guess