blocks|key|1639583|text|这里有一个跨平台的文件锁定模块：Portalocker|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1639584|尽管如Kevin所说，如果可能的话，同时从多个进程写入文件是您想要避免的事情。|1639585|如果你能把你的问题硬塞进数据库，你就可以使用SQLite。它支持并发访问，并处理自己的锁定。|1639586|entityMap|0|LINK|mutability|MUTABLE|url|https://pypi.python.org/pypi/portalocker^0|G|B|0|0|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@$A|Q|B|R|1|S]]|C|$]]|$1|D|3|E|5|6|7|T|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|U|8|@]|9|@]|C|$]]|$1|H|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|I|$J|$5|K|L|M|C|$N|O]]]]

There is a cross-platform file locking module here: <a href="https://pypi.python.org/pypi/portalocker" rel="noreferrer">Portalocker</a>

Although as Kevin says, writing to a file from multiple processes at once is something you want to avoid if at all possible.

If you can shoehorn your problem into a database, you could use SQLite. It supports concurrent access and handles its own locking.

blocks|key|1424615|text|在操作系统级别协调对单个文件的访问充满了您可能不想解决的各种问题。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1424616|最好的办法是有一个单独的进程来协调对该文件的读/写访问。|1424617|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

Coordinating access to a single file at the OS level is fraught with all kinds of issues that you probably don't want to solve.

Your best bet is have a separate process that coordinates read/write access to that file.

blocks|key|1424533|text|锁定文件通常是特定于平台的操作，因此您可能需要考虑在不同操作系统上运行的可能性。例如：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1424534|import+os

def+my_lock(f):
++++if+os.name+==+"posix":
++++++++#+Unix+or+OS+X+specific+locking+here
++++elif+os.name+==+"nt":
++++++++#+Windows+specific+locking+here
++++else:
++++++++print+"Unknown+operating+system,+lock+unavailable"|code-block|syntax|javascript|1424535|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Locking a file is usually a platform-specific operation, so you may need to allow for the possibility of running on different operating systems. For example:

<pre><code>import os

def my_lock(f):
 if os.name == "posix":
 # Unix or OS X specific locking here
 elif os.name == "nt":
 # Windows specific locking here
 else:
 print "Unknown operating system, lock unavailable"
</code></pre>

blocks|key|1424760|text|我一直在处理这样一种情况，即我从同一目录/文件夹中运行同一程序的多个副本，并记录错误。我的方法是在打开日志文件之前向光盘写入一个“锁定文件”。程序在继续之前检查“锁文件”是否存在，如果“锁文件”存在，则等待轮到它。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1424761|代码如下：|1424762|def+errlogger(error):

++++while+True:
++++++++if+not+exists('errloglock'):
++++++++++++lock+=+open('errloglock',+'w')
++++++++++++if+exists('errorlog'):+log+=+open('errorlog',+'a')
++++++++++++else:+log+=+open('errorlog',+'w')
++++++++++++log.write(str(datetime.utcnow())[0:-7]+%2B+'+'+%2B+error+%2B+'\n')
++++++++++++log.close()
++++++++++++remove('errloglock')
++++++++++++return
++++++++else:
++++++++++++check+=+stat('errloglock')
++++++++++++if+time()+-+check.st_ctime+>+0.01:+remove('errloglock')
++++++++++++print('waiting+my+turn')|code-block|syntax|javascript|1424763|编辑-在考虑了上面关于陈旧锁的一些评论之后，我编辑了代码，添加了对“锁文件”的陈旧检查。在我的系统上计时这个函数的几千次迭代，平均0.002066次...之前的秒数：|1424764|lock+=+open('errloglock',+'w')|1424765|到紧接着：|1424766|remove('errloglock')|1424767|因此，我认为我将从5倍的数量开始，以表明陈旧并监控问题的情况。|1424768|此外，当我在计时时，我意识到我有一些并不是真正必要的代码：|1424769|lock.close()|1424770|它紧跟在open语句之后，所以我在这个编辑中删除了它。|1424771|entityMap^0|0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|11|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|12|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|13|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|14|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|15|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|16|8|@]|9|@]|A|$G|H]]|$1|Q|3|R|5|6|7|17|8|@]|9|@]|A|$]]|$1|S|3|T|5|6|7|18|8|@]|9|@]|A|$]]|$1|U|3|V|5|F|7|19|8|@]|9|@]|A|$G|H]]|$1|W|3|X|5|6|7|1A|8|@]|9|@]|A|$]]|$1|Y|3|-4|5|6|7|1B|8|@]|9|@]|A|$]]]|Z|$]]

I have been working on a situation like this where I run multiple copies of the same program from within the same directory/folder and logging errors. My approach was to write a "lock file" to the disc before opening the log file. The program checks for the presence of the "lock file" before proceeding, and waits for its turn if the "lock file" exists.

Here is the code:

<pre><code>def errlogger(error):

 while True:
 if not exists('errloglock'):
 lock = open('errloglock', 'w')
 if exists('errorlog'): log = open('errorlog', 'a')
 else: log = open('errorlog', 'w')
 log.write(str(datetime.utcnow())[0:-7] + ' ' + error + '\n')
 log.close()
 remove('errloglock')
 return
 else:
 check = stat('errloglock')
 if time() - check.st_ctime &gt; 0.01: remove('errloglock')
 print('waiting my turn')
</code></pre>

EDIT---
After thinking over some of the comments about stale locks above I edited the code to add a check for staleness of the "lock file." Timing several thousand iterations of this function on my system gave and average of 0.002066... seconds from just before:

<pre><code>lock = open('errloglock', 'w')
</code></pre>

to just after:

<pre><code>remove('errloglock')
</code></pre>

so I figured I will start with 5 times that amount to indicate staleness and monitor the situation for problems.

Also, as I was working with the timing, I realized that I had a bit of code that was not really necessary:

<pre><code>lock.close()
</code></pre>

which I had immediately following the open statement, so I have removed it in this edit.

blocks|key|1639815|text|下面是一个如何使用与Evan+Fossmark's+implementation类似的filelock库的示例|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1639816|from+filelock+import+FileLock

lockfile+=+r"c:\scr.txt"
lock+=+FileLock(lockfile+%2B+".lock")
with+lock:
++++file+=+open(path,+"w")
++++file.write("123")
++++file.close()|code-block|syntax|javascript|1639817|with+lock:块中的任何代码都是线程安全的，这意味着它将在另一个进程访问该文件之前完成。|style|CODE|1639818|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/498505|1|https://pypi.org/project/filelock/^0|A|U|0|17|8|1|0|0|0|A|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@$A|X|B|Y|1|Z]|$A|10|B|11|1|12]]|C|$]]|$1|D|3|E|5|F|7|13|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|14|8|@$A|15|B|16|K|L]]|9|@]|C|$]]|$1|M|3|-4|5|6|7|17|8|@]|9|@]|C|$]]]|N|$O|$5|P|Q|R|C|$S|T]]|U|$5|P|Q|R|C|$S|V]]]]

Here's an example of how to use the <a href="https://pypi.org/project/filelock/" rel="nofollow noreferrer">filelock</a> library, which is similar to <a href="https://stackoverflow.com/a/498505">Evan Fossmark's implementation</a>:
<pre><code>from filelock import FileLock

lockfile = r&quot;c:\scr.txt&quot;
lock = FileLock(lockfile + &quot;.lock&quot;)
with lock:
 file = open(path, &quot;w&quot;)
 file.write(&quot;123&quot;)
 file.close()
</code></pre>
Any code within the <code>with lock:</code> block is thread-safe, meaning that it will be finished before another process has access to the file.

blocks|key|1639891|text|这对我很有效:不要占用大文件，将文件分成几个小文件，创建文件Temp，删除文件A，然后将文件Temp重命名为A。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1639892|import+os
import+json

def+Server():
++++i+=+0
++++while+i+==+0:
++++++++try:++++++++
++++++++++++++++with+open(File_Temp,+"w")+as+file:
++++++++++++++++++++json.dump(DATA,+file,+indent=2)
++++++++++++++++if+os.path.exists(File_A):
++++++++++++++++++++os.remove(File_A)
++++++++++++++++os.rename(File_Temp,+File_A)
++++++++++++++++i+=+1
++++++++except+OSError+as+e:
++++++++++++++++print+("file+locked:+"+,str(e))
++++++++++++++++time.sleep(1)
++++++++++++
++++++++++++
def+Clients():
++++i+=+0
++++while+i+==+0:
++++++++try:
++++++++++++if+os.path.exists(File_A):
++++++++++++++++with+open(File_A,"r")+as+file:
++++++++++++++++++++DATA_Temp+=+file.read()
++++++++++++DATA+=+json.loads(DATA_Temp)
++++++++++++i+=+1
++++++++except+OSError+as+e:
++++++++++++print+(str(e))
++++++++++++time.sleep(1)|code-block|syntax|javascript|1639893|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

this worked for me:
Do not occupy large files, distribute in several small ones
you create file Temp, delete file A and then rename file Temp to A.
<pre><code>import os
import json

def Server():
 i = 0
 while i == 0:
 try: 
 with open(File_Temp, &quot;w&quot;) as file:
 json.dump(DATA, file, indent=2)
 if os.path.exists(File_A):
 os.remove(File_A)
 os.rename(File_Temp, File_A)
 i = 1
 except OSError as e:
 print (&quot;file locked: &quot; ,str(e))
 time.sleep(1)
 
 
def Clients():
 i = 0
 while i == 0:
 try:
 if os.path.exists(File_A):
 with open(File_A,&quot;r&quot;) as file:
 DATA_Temp = file.read()
 DATA = json.loads(DATA_Temp)
 i = 1
 except OSError as e:
 print (str(e))
 time.sleep(1)
</code></pre>

blocks|key|1424714|text|我在grizzled-python中找到了一个简单有效的(！)+implementation。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1424715|简单地使用os.open(...，O_EXCL)+%2B+os.close()在windows上不起作用。|1424716|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/bmc/grizzled-python/blob/master/grizzled/io/filelock.py^0|W|E|0|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]]|C|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@]|C|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|C|$]]]|G|$H|$5|I|J|K|C|$L|M]]]]

I found a simple and worked(!) <a href="https://github.com/bmc/grizzled-python/blob/master/grizzled/io/filelock.py" rel="nofollow">implementation</a> from grizzled-python.

Simple use os.open(..., O_EXCL) + os.close() didn't work on windows.

blocks|key|1639768|text|您可能会发现pylocker非常有用。它通常可用于锁定文件或用于锁定机制，并且可以同时从多个Python进程访问。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1639769|如果你只是想锁定一个文件，下面是它的工作原理：|1639770|import+uuid
from+pylocker+import+Locker

#++create+a+unique+lock+pass.+This+can+be+any+string.
lpass+=+str(uuid.uuid1())

#+create+locker+instance.
FL+=+Locker(filePath='myfile.txt',+lockPass=lpass,+mode='w')

#+aquire+the+lock
with+FL+as+r:
++++#+get+the+result
++++acquired,+code,+fd++=+r

++++#+check+if+aquired.
++++if+fd+is+not+None:
++++++++print+fd
++++++++fd.write("I+have+succesfuly+aquired+the+lock+!")

#+no+need+to+release+anything+or+to+close+the+file+descriptor,+
#+with+statement+takes+care+of+that.+let's+print+fd+and+verify+that.
print+fd|code-block|syntax|javascript|1639771|entityMap|0|LINK|mutability|MUTABLE|url|https://bachiraoun.github.io/pylocker/^0|6|8|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|6|7|W|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|X|8|@]|9|@]|C|$I|J]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]]]

You may find <a href="https://bachiraoun.github.io/pylocker/" rel="nofollow noreferrer">pylocker</a> very useful. It can be used to lock a file or for locking mechanisms in general and can be accessed from multiple Python processes at once. 

If you simply want to lock a file here's how it works: 

<pre><code>import uuid
from pylocker import Locker

# create a unique lock pass. This can be any string.
lpass = str(uuid.uuid1())

# create locker instance.
FL = Locker(filePath='myfile.txt', lockPass=lpass, mode='w')

# aquire the lock
with FL as r:
 # get the result
 acquired, code, fd = r

 # check if aquired.
 if fd is not None:
 print fd
 fd.write("I have succesfuly aquired the lock !")

# no need to release anything or to close the file descriptor, 
# with statement takes care of that. let's print fd and verify that.
print fd
</code></pre>

I need to lock a file for writing in Python. It will be accessed from multiple Python processes at once. I have found some solutions online, but most fail for my purposes as they are often only Unix based or Windows based.

Locking a file in Python

日志文件

数据库

Windows

SQLite

Python

Unix

我需要锁定一个文件，以便在Python中写入。它将同时从多个Python进程访问。我在网上找到了一些解决方案，但大多数都失败了，因为它们通常只基于Unix或Windows。

问在Python中锁定文件
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