将追加列表更新为txt文件

问题描述

您好，我目前正在研究python，我想知道如何在txtfile不断变化的情况下附加列表。措辞很难，这里的代码仍然是

list=[]
random_number=0
file_handler=open("history.txt","w")
file_handler.write(str(list))
lenght_cumulative_data=len(list)
confirmed.append(random_number)

现在我要完成的是将数字0的列表变量显示在history.txt中，但是那没有发生，并且可以想象一下random_number总是在变化，我希望列表变量能够始终更新自身。就像如果让random_number更改为1，然后再更改2一样，我希望列表更新为[0,1,2]。你是怎样做的？我一直在youtube上搜索，他们给我的就是这个写功能，无论如何有人可以推荐它或有任何想法吗？

解决方法

from os import stat
from _thread import start_new_thread
from time import sleep

List = []

class WatchFileForChanges:
    def __init__(self,filename):
        self.file = filename
        self.cached_file = stat(self.file).st_mtime

    def watch(self):
        num = 0
        while 1:
            status = stat(self.file).st_mtime
            if status != self.cached_file:
                self.cached_file = status
                #file changed
                List.append(num)
                num += 1

def main():

    Watcher = WatchFileForChanges("file.txt")

    start_new_thread(Watcher.watch,())

    while 1:
        print(List)
        sleep(1)


if __name__ == '__main__':
    main()

这将做您想要的。如果我对您的理解正确，那么您希望每次文件更改时都将其添加到列表中。

注意：此答案仅适用于Windows

changes.py：

# Adapted from http://timgolden.me.uk/python/win32_how_do_i/watch_directory_for_changes.html

import threading
import os

import win32file
import win32con

ACTIONS = {
    1 : "Created",2 : "Deleted",3 : "Updated",4 : "Renamed from something",5 : "Renamed to something"
}
# Thanks to Claudio Grondi for the correct set of numbers
FILE_LIST_DIRECTORY = 0x0001

def monitor_changes(callback,path,filenames):
    path = path or ""
    if type(filenames) == "str":
        filenames = (filenames,)

    thread = threading.Thread(target=_monitor,args=(callback,filenames))
    thread.start()

    return thread

def _monitor(callback,filenames):
    hDir = win32file.CreateFile (
        path,FILE_LIST_DIRECTORY,win32con.FILE_SHARE_READ | win32con.FILE_SHARE_WRITE | win32con.FILE_SHARE_DELETE,None,win32con.OPEN_EXISTING,win32con.FILE_FLAG_BACKUP_SEMANTICS,None
    )
    while True:
        #
        # ReadDirectoryChangesW takes a previously-created
        # handle to a directory,a buffer size for results,# a flag to indicate whether to watch subtrees and
        # a filter of what changes to notify.
        #
        # NB Tim Juchcinski reports that he needed to up
        # the buffer size to be sure of picking up all
        # events when a large number of files were
        # deleted at once.
        #
        results = win32file.ReadDirectoryChangesW (
            hDir,1024,True,win32con.FILE_NOTIFY_CHANGE_LAST_WRITE,None
        )

        for action,file in results:
            if filenames and file not in filenames and os.path.basename(file) not in filenames:
                continue
            callback(action,file)

if __name__ == '__main__':
    # monitor by printing
    t = monitor_changes(print,".",None)

在您的main.py中：

import changes
import os

my_list = []

def callback(action_id,filename):
    # the function running means
    # that the file has been modified
    
    action_desc = changes.ACTIONS[action_id]
    print(action_desc,filename)

    with open(filename) as f:
        my_list.append(f.read())

thread = changes.monitor_changes(callback,"my_file_that_I_want_to_monitor.txt")

如果要监视目录中的所有文件，请以monitor_changes作为第三个参数调用None。

注意：这将监视所有子目录，因此具有相同名称但位于不同文件夹中的文件将触发回调。如果要避免这种情况，请检查传递给回调函数的文件名是否确实要监视。

python self-updating