Python程序在不需要的时候不断循环

Question

我有我的代码，但它似乎没有按预期工作。它需要向用户请求输入来搜索一个文件，一旦找到就不再询问，而是继续询问。但是我想让它再次询问用户是否还没有找到文件。我的代码如下：

import os, sys
from stat import *
from os.path import join

while True:
    lookfor=input("\nPlease enter file name and extension for search? \n")
    for root, dirs, files in os.walk("C:\\"):
        print("Searching", root)
        if lookfor in files:
            print("Found %s" % join(root, lookfor))
            break
        else:
            print ("File not found, please try again")

Answer 1

break只是中止内部for循环。您可以简单地使用助手变量：

import os, sys

while True:
    lookfor=input("\nPlease enter file name and extension for search? \n")
    found = False
    for root, dirs, files in os.walk("C:\\"):
        print("Searching", root)
        if lookfor in files:
            print("Found %s" % os.path.join(root, lookfor))
            found = True
            break
     if found:
         break
     print ("File not found, please try again")

或者，将其设为函数并使用return：

def search():
    while True:
        lookfor=input("\nPlease enter file name and extension for search? \n")
        for root, dirs, files in os.walk("C:\\"):
            print("Searching", root)
            if lookfor in files:
                print("Found %s" % os.path.join(root, lookfor))
                return
        print ("File not found, please try again")
search()

也可以使用^{} construct：

while True:
    lookfor=input("\nPlease enter file name and extension for search? \n")
    for root, dirs, files in os.walk("C:\\"):
        print("Searching", root)
        if lookfor in files:
            print("Found %s" % os.path.join(root, lookfor))
            break
    else:
        print ("File not found, please try again")
        continue
    break

Answer 2

break在for循环中，因此它只会将您从for循环中分离出来，而不是while循环。你知道吗

import os, sys
from stat import *
from os.path import join

condition=True 

while condition:
    lookfor=input("\nPlease enter file name and extension for search? \n")
    for root, dirs, files in os.walk("C:\\"):
        print("Searching", root)
        if lookfor in files:
            print("Found %s" % join(root, lookfor))
            condition = False      #set condition to False and then break
            break
        else:
            print ("File not found, please try again")

Answer 3

问题是你只打破了内部循环（即for）。你知道吗

您可以将其放入函数中并返回而不是中断，或者引发并捕获异常，如下所示：Breaking out of nested loops