Python函数和变量的麻烦 [英] Python functions and variables trouble

问题描述

到目前为止，我已经创建了此代码...

  def print_slow(str):对于str中的字母:sys.stdout.write(字母)sys.stdout.flush()time.sleep(0.005)def menu():print_slow("------------- [MENU] -------------")打印(" ")print_slow("1)输入一个句子.")打印(" ")print_slow("2)查找单词的位置.")打印(" ")print_slow("--------------------------------")打印(" ")print_slow(>>>")选择= str(input(")))打印(" ")time.sleep(0.5)如果选择=="1":选项1()如果选择=="2":option2()def option1():print_slow(输入句子")句子= str(input(:"))打印(" ")菜单()def option2():如果不是句子:print_slow(请先输入一个句子！")time.sleep(0.5)打印(" ")别的:句子Uppercase =句子.upper()[代码继续...] 

基本上，当我测试它时，我首先按下选项2，它应该给出输出请先输入一个句子！".

然后我按菜单中的选项1，它会提示我输入一个句子(我把我的名字叫鲍勃"作为测试)，并且确实如此.

我在输入句子后按了选项2，它应该继续输入我的代码-而是显示错误消息请先输入句子！"

我该如何解决?

解决方案

您正在函数 option1 中设置 local 变量 sentence .该变量在 option2 中不可见，因为它仅位于 option1 内部，并且在 option1 完成后将被清除.

如果要共享变量，则需要至少在 option1 中将其定义为 global :

  def option1():print_slow(输入句子")全局句句子= str(input(:"))打印(" ")菜单() 

但是请注意，使用全局变量通常是不良代码质量的标志.在您的情况下，让 option1 返回 sentence 到 main 并从 main 传递它会更有意义.到 option2 .

I have created this code so far...

def print_slow(str):
    for letter in str:
        sys.stdout.write(letter)
        sys.stdout.flush()
        time.sleep(0.005)

def menu():
    print_slow("-------------[MENU]-------------")
    print(" ")
    print_slow("1) Enter a sentence.")
    print(" ")
    print_slow("2) Find the position of  a word.")
    print(" ")
    print_slow("--------------------------------")
    print(" ")

    print_slow(">>> ")
    choice = str(input(" "))
    print(" ")
    time.sleep(0.5)

    if choice == "1":
        option1()
    if choice == "2":
        option2()

def option1():
    print_slow("Enter sentence")
    sentence = str(input(": "))
    print(" ")
    menu()

def option2():
    if not sentence:
        print_slow("Please enter a sentence first!")
        time.sleep(0.5)
        print(" ")

    else:
        sentenceUppercase = sentence.upper()
        [code goes on...]

Basically when I test it, I press option 2 first and it should give the output 'Please enter a sentence first!', which it does.

I then press option 1 in the menu and it should prompt me to input a sentence (I put 'my name is bob' as a test) and it does.

I then pressed option 2 after inputting the sentence and it should continue with my code - instead it gives the error message 'Please enter a sentence first!'

How can I fix this??

解决方案

You're setting a local variable sentence inside function option1. This variable is not visible in option2 since it lives inside option1 only and will be cleaned up once option1 is finished.

If you want to share the variable, you need to define it as global at least in option1:

def option1():
    print_slow("Enter sentence")
    global sentence
    sentence = str(input(": "))
    print(" ")
    menu()

Note, however, that using global variables is usually a sign of bad code quality. In your case, it would make more sense to have option1 return sentence to main, and pass it from main to option2.

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