Related
I am having an issue writing to a NamedTemporaryFile in Python and then reading it back. The function downloads a file via tftpy to the temp file, reads it, hashes the contents, and then compares the hash digest to the original file. The function in question is below:
def verify_upload(self, image, destination):
# create a tftp client
client = TftpClient(ip, 69, localip=self.binding_ip)
# generate a temp file to hold the download info
if not os.path.exists("temp"):
os.makedirs("temp")
with NamedTemporaryFile(dir="temp") as tempfile, open(image, 'r') as original:
try:
# attempt to download the target image
client.download(destination, tempfile, timeout=self.download_timeout)
except TftpTimeout:
raise RuntimeError("Could not download {0} from {1} for verification".format(destination, self.target_ip))
# hash the original file and the downloaded version
original_digest = hashlib.sha256(original.read()).hexdigest()
uploaded_digest = hashlib.sha256(tempfile.read()).hexdigest()
if self.verbose:
print "Original SHA-256: {0}\nUploaded SHA-256: {1}".format(original_digest, uploaded_digest)
# return the hash comparison
return original_digest == uploaded_digest
The problem is that every time I try to execute the line uploaded_digest = hashlib.sha256(tempfile.read()).hexdigest() the application errors out with a ValueError - I/O Operation on a closed file. Since the with block is not complete I am struggling to understand why the temp file would be closed. The only possibility I can think of is that tftpy is closing the file after doing the download, but I cannot find any point in the tftpy source where this would be happening. Note, I have also tried inserting the line tempfile.seek(0) in order to put the file back in a proper state for reading, however this also gives me the ValueError.
Is tftpy closing the file possibly? I read that there is possibly a bug in NamedTemporaryFile causing this problem? Why is the file closed before the reference defined by the with block goes out of scope?
TFTPy is closing the file. When you were looking at the source, you missed the following code path:
class TftpClient(TftpSession):
...
def download(self, filename, output, packethook=None, timeout=SOCK_TIMEOUT):
...
self.context = TftpContextClientDownload(self.host,
self.iport,
filename,
output,
self.options,
packethook,
timeout,
localip = self.localip)
self.context.start()
# Download happens here
self.context.end() # <--
TftpClient.download calls TftpContextClientDownload.end:
class TftpContextClientDownload(TftpContext):
...
def end(self):
"""Finish up the context."""
TftpContext.end(self) # <--
self.metrics.end_time = time.time()
log.debug("Set metrics.end_time to %s", self.metrics.end_time)
self.metrics.compute()
TftpContextClientDownload.end calls TftpContext.end:
class TftpContext(object):
...
def end(self):
"""Perform session cleanup, since the end method should always be
called explicitely by the calling code, this works better than the
destructor."""
log.debug("in TftpContext.end")
self.sock.close()
if self.fileobj is not None and not self.fileobj.closed:
log.debug("self.fileobj is open - closing")
self.fileobj.close() # <--
and TftpContext.end closes the file.
I'm using fabric to connect to remote host, when i'm there, I try to call a script that I made (It parses the file I give in argument). But when I call the script from inside my Fabfile.py, it assumes the path I gave is from the machine I launch the fabfile from (so not my remote host)
In my fabfile.py I have:
Import import servclasse
env.host='host1'
def listconf():
#here I browes to the correct folder
s=servclasse.Server("my.file") #this is where I want it to open the host1:my.file file and instanciate a classe from what it parsed
If i do this, it tries to open the file from the folder where servclass.py is. Is there a way to give a "remote path" in argument? I would rather not downloading the file.
Should I upload the script servclasse.py with the operation.put before calling it?
Edit: more info
In my servclasse I have this:
def __init__(self, path):
self.config = ConfigParser.ConfigParser(allow_no_value=True)
self.config.readfp(open(path))
The function open() was the problem.
I figured out how to do it so i'll drop it here in case someone read this topic one day :
def listconf():
#first I browes to the correct folder then
contents = StringIO.StringIO()
get("MyFile",contents)
contents.seek(0)
s=Server(contents)
and in the servclass.py
def __init__(self, objfile):
self.config = ConfigParser.ConfigParser(allow_no_value=True)
self.config.readfp(objfile)
#and i do my stuffs
I have a log file being written by another process which I want to watch for changes. Each time a change occurs I'd like to read the new data in to do some processing on it.
What's the best way to do this? I was hoping there'd be some sort of hook from the PyWin32 library. I've found the win32file.FindNextChangeNotification function but have no idea how to ask it to watch a specific file.
If anyone's done anything like this I'd be really grateful to hear how...
[Edit] I should have mentioned that I was after a solution that doesn't require polling.
[Edit] Curses! It seems this doesn't work over a mapped network drive. I'm guessing windows doesn't 'hear' any updates to the file the way it does on a local disk.
Did you try using Watchdog?
Python API library and shell utilities to monitor file system events.
Directory monitoring made easy with
A cross-platform API.
A shell tool to run commands in response to directory changes.
Get started quickly with a simple example in Quickstart...
If polling is good enough for you, I'd just watch if the "modified time" file stat changes. To read it:
os.stat(filename).st_mtime
(Also note that the Windows native change event solution does not work in all circumstances, e.g. on network drives.)
import os
class Monkey(object):
def __init__(self):
self._cached_stamp = 0
self.filename = '/path/to/file'
def ook(self):
stamp = os.stat(self.filename).st_mtime
if stamp != self._cached_stamp:
self._cached_stamp = stamp
# File has changed, so do something...
If you want a multiplatform solution, then check QFileSystemWatcher.
Here an example code (not sanitized):
from PyQt4 import QtCore
#QtCore.pyqtSlot(str)
def directory_changed(path):
print('Directory Changed!!!')
#QtCore.pyqtSlot(str)
def file_changed(path):
print('File Changed!!!')
fs_watcher = QtCore.QFileSystemWatcher(['/path/to/files_1', '/path/to/files_2', '/path/to/files_3'])
fs_watcher.connect(fs_watcher, QtCore.SIGNAL('directoryChanged(QString)'), directory_changed)
fs_watcher.connect(fs_watcher, QtCore.SIGNAL('fileChanged(QString)'), file_changed)
It should not work on windows (maybe with cygwin ?), but for unix user, you should use the "fcntl" system call. Here is an example in Python. It's mostly the same code if you need to write it in C (same function names)
import time
import fcntl
import os
import signal
FNAME = "/HOME/TOTO/FILETOWATCH"
def handler(signum, frame):
print "File %s modified" % (FNAME,)
signal.signal(signal.SIGIO, handler)
fd = os.open(FNAME, os.O_RDONLY)
fcntl.fcntl(fd, fcntl.F_SETSIG, 0)
fcntl.fcntl(fd, fcntl.F_NOTIFY,
fcntl.DN_MODIFY | fcntl.DN_CREATE | fcntl.DN_MULTISHOT)
while True:
time.sleep(10000)
Check out pyinotify.
inotify replaces dnotify (from an earlier answer) in newer linuxes and allows file-level rather than directory-level monitoring.
For watching a single file with polling, and minimal dependencies, here is a fully fleshed-out example, based on answer from Deestan (above):
import os
import sys
import time
class Watcher(object):
running = True
refresh_delay_secs = 1
# Constructor
def __init__(self, watch_file, call_func_on_change=None, *args, **kwargs):
self._cached_stamp = 0
self.filename = watch_file
self.call_func_on_change = call_func_on_change
self.args = args
self.kwargs = kwargs
# Look for changes
def look(self):
stamp = os.stat(self.filename).st_mtime
if stamp != self._cached_stamp:
self._cached_stamp = stamp
# File has changed, so do something...
print('File changed')
if self.call_func_on_change is not None:
self.call_func_on_change(*self.args, **self.kwargs)
# Keep watching in a loop
def watch(self):
while self.running:
try:
# Look for changes
time.sleep(self.refresh_delay_secs)
self.look()
except KeyboardInterrupt:
print('\nDone')
break
except FileNotFoundError:
# Action on file not found
pass
except:
print('Unhandled error: %s' % sys.exc_info()[0])
# Call this function each time a change happens
def custom_action(text):
print(text)
watch_file = 'my_file.txt'
# watcher = Watcher(watch_file) # simple
watcher = Watcher(watch_file, custom_action, text='yes, changed') # also call custom action function
watcher.watch() # start the watch going
Well after a bit of hacking of Tim Golden's script, I have the following which seems to work quite well:
import os
import win32file
import win32con
path_to_watch = "." # look at the current directory
file_to_watch = "test.txt" # look for changes to a file called test.txt
def ProcessNewData( newData ):
print "Text added: %s"%newData
# Set up the bits we'll need for output
ACTIONS = {
1 : "Created",
2 : "Deleted",
3 : "Updated",
4 : "Renamed from something",
5 : "Renamed to something"
}
FILE_LIST_DIRECTORY = 0x0001
hDir = win32file.CreateFile (
path_to_watch,
FILE_LIST_DIRECTORY,
win32con.FILE_SHARE_READ | win32con.FILE_SHARE_WRITE,
None,
win32con.OPEN_EXISTING,
win32con.FILE_FLAG_BACKUP_SEMANTICS,
None
)
# Open the file we're interested in
a = open(file_to_watch, "r")
# Throw away any exising log data
a.read()
# Wait for new data and call ProcessNewData for each new chunk that's written
while 1:
# Wait for a change to occur
results = win32file.ReadDirectoryChangesW (
hDir,
1024,
False,
win32con.FILE_NOTIFY_CHANGE_LAST_WRITE,
None,
None
)
# For each change, check to see if it's updating the file we're interested in
for action, file in results:
full_filename = os.path.join (path_to_watch, file)
#print file, ACTIONS.get (action, "Unknown")
if file == file_to_watch:
newText = a.read()
if newText != "":
ProcessNewData( newText )
It could probably do with a load more error checking, but for simply watching a log file and doing some processing on it before spitting it out to the screen, this works well.
Thanks everyone for your input - great stuff!
Check my answer to a similar question. You could try the same loop in Python. This page suggests:
import time
while 1:
where = file.tell()
line = file.readline()
if not line:
time.sleep(1)
file.seek(where)
else:
print line, # already has newline
Also see the question tail() a file with Python.
This is another modification of Tim Goldan's script that runs on unix types and adds a simple watcher for file modification by using a dict (file=>time).
usage: whateverName.py path_to_dir_to_watch
#!/usr/bin/env python
import os, sys, time
def files_to_timestamp(path):
files = [os.path.join(path, f) for f in os.listdir(path)]
return dict ([(f, os.path.getmtime(f)) for f in files])
if __name__ == "__main__":
path_to_watch = sys.argv[1]
print('Watching {}..'.format(path_to_watch))
before = files_to_timestamp(path_to_watch)
while 1:
time.sleep (2)
after = files_to_timestamp(path_to_watch)
added = [f for f in after.keys() if not f in before.keys()]
removed = [f for f in before.keys() if not f in after.keys()]
modified = []
for f in before.keys():
if not f in removed:
if os.path.getmtime(f) != before.get(f):
modified.append(f)
if added: print('Added: {}'.format(', '.join(added)))
if removed: print('Removed: {}'.format(', '.join(removed)))
if modified: print('Modified: {}'.format(', '.join(modified)))
before = after
Here is a simplified version of Kender's code that appears to do the same trick and does not import the entire file:
# Check file for new data.
import time
f = open(r'c:\temp\test.txt', 'r')
while True:
line = f.readline()
if not line:
time.sleep(1)
print 'Nothing New'
else:
print 'Call Function: ', line
Well, since you are using Python, you can just open a file and keep reading lines from it.
f = open('file.log')
If the line read is not empty, you process it.
line = f.readline()
if line:
// Do what you want with the line
You may be missing that it is ok to keep calling readline at the EOF. It will just keep returning an empty string in this case. And when something is appended to the log file, the reading will continue from where it stopped, as you need.
If you are looking for a solution that uses events, or a particular library, please specify this in your question. Otherwise, I think this solution is just fine.
Simplest solution for me is using watchdog's tool watchmedo
From https://pypi.python.org/pypi/watchdog I now have a process that looks up the sql files in a directory and executes them if necessary.
watchmedo shell-command \
--patterns="*.sql" \
--recursive \
--command='~/Desktop/load_files_into_mysql_database.sh' \
.
As you can see in Tim Golden's article, pointed by Horst Gutmann, WIN32 is relatively complex and watches directories, not a single file.
I'd like to suggest you look into IronPython, which is a .NET python implementation.
With IronPython you can use all the .NET functionality - including
System.IO.FileSystemWatcher
Which handles single files with a simple Event interface.
This is an example of checking a file for changes. One that may not be the best way of doing it, but it sure is a short way.
Handy tool for restarting application when changes have been made to the source. I made this when playing with pygame so I can see effects take place immediately after file save.
When used in pygame make sure the stuff in the 'while' loop is placed in your game loop aka update or whatever. Otherwise your application will get stuck in an infinite loop and you will not see your game updating.
file_size_stored = os.stat('neuron.py').st_size
while True:
try:
file_size_current = os.stat('neuron.py').st_size
if file_size_stored != file_size_current:
restart_program()
except:
pass
In case you wanted the restart code which I found on the web. Here it is. (Not relevant to the question, though it could come in handy)
def restart_program(): #restart application
python = sys.executable
os.execl(python, python, * sys.argv)
Have fun making electrons do what you want them to do.
Seems that no one has posted fswatch. It is a cross-platform file system watcher. Just install it, run it and follow the prompts.
I've used it with python and golang programs and it just works.
ACTIONS = {
1 : "Created",
2 : "Deleted",
3 : "Updated",
4 : "Renamed from something",
5 : "Renamed to something"
}
FILE_LIST_DIRECTORY = 0x0001
class myThread (threading.Thread):
def __init__(self, threadID, fileName, directory, origin):
threading.Thread.__init__(self)
self.threadID = threadID
self.fileName = fileName
self.daemon = True
self.dir = directory
self.originalFile = origin
def run(self):
startMonitor(self.fileName, self.dir, self.originalFile)
def startMonitor(fileMonitoring,dirPath,originalFile):
hDir = win32file.CreateFile (
dirPath,
FILE_LIST_DIRECTORY,
win32con.FILE_SHARE_READ | win32con.FILE_SHARE_WRITE,
None,
win32con.OPEN_EXISTING,
win32con.FILE_FLAG_BACKUP_SEMANTICS,
None
)
# Wait for new data and call ProcessNewData for each new chunk that's
# written
while 1:
# Wait for a change to occur
results = win32file.ReadDirectoryChangesW (
hDir,
1024,
False,
win32con.FILE_NOTIFY_CHANGE_LAST_WRITE,
None,
None
)
# For each change, check to see if it's updating the file we're
# interested in
for action, file_M in results:
full_filename = os.path.join (dirPath, file_M)
#print file, ACTIONS.get (action, "Unknown")
if len(full_filename) == len(fileMonitoring) and action == 3:
#copy to main file
...
Since I have it installed globally, my favorite approach is to use nodemon. If your source code is in src, and your entry point is src/app.py, then it's as easy as:
nodemon -w 'src/**' -e py,html --exec python src/app.py
... where -e py,html lets you control what file types to watch for changes.
Here's an example geared toward watching input files that write no more than one line per second but usually a lot less. The goal is to append the last line (most recent write) to the specified output file. I've copied this from one of my projects and just deleted all the irrelevant lines. You'll have to fill in or change the missing symbols.
from PyQt5.QtCore import QFileSystemWatcher, QSettings, QThread
from ui_main_window import Ui_MainWindow # Qt Creator gen'd
class MainWindow(QMainWindow, Ui_MainWindow):
def __init__(self, parent=None):
QMainWindow.__init__(self, parent)
Ui_MainWindow.__init__(self)
self._fileWatcher = QFileSystemWatcher()
self._fileWatcher.fileChanged.connect(self.fileChanged)
def fileChanged(self, filepath):
QThread.msleep(300) # Reqd on some machines, give chance for write to complete
# ^^ About to test this, may need more sophisticated solution
with open(filepath) as file:
lastLine = list(file)[-1]
destPath = self._filemap[filepath]['dest file']
with open(destPath, 'a') as out_file: # a= append
out_file.writelines([lastLine])
Of course, the encompassing QMainWindow class is not strictly required, ie. you can use QFileSystemWatcher alone.
Just to put this out there since no one mentioned it: there's a Python module in the Standard Library named filecmp which has this cmp() function that compares two files.
Just make sure you don't do from filecmp import cmp to not overshadow the built-in cmp() function in Python 2.x. That's okay in Python 3.x, though, since there's no such built-in cmp() function anymore.
Anyway, this is how its use looks like:
import filecmp
filecmp.cmp(path_to_file_1, path_to_file_2, shallow=True)
The argument shallow defaults to True. If the argument's value is True, then only the metadata of the files are compared; however, if the argument's value is False, then the contents of the files are compared.
Maybe this information will be useful to someone.
watchfiles (https://github.com/samuelcolvin/watchfiles) is a Python API and CLI that uses the Notify (https://github.com/notify-rs/notify) library written in Rust.
The rust implementation currently (2022-10-09) supports:
Linux / Android: inotify
macOS: FSEvents or kqueue, see features
Windows: ReadDirectoryChangesW
FreeBSD / NetBSD / OpenBSD / DragonflyBSD: kqueue
All platforms: polling
Binaries available on PyPI (https://pypi.org/project/watchfiles/) and conda-forge (https://github.com/conda-forge/watchfiles-feedstock).
You can also use a simple library called repyt, here is an example:
repyt ./app.py
related #4Oh4 solution a smooth change for a list of files to watch;
import os
import sys
import time
class Watcher(object):
running = True
refresh_delay_secs = 1
# Constructor
def __init__(self, watch_files, call_func_on_change=None, *args, **kwargs):
self._cached_stamp = 0
self._cached_stamp_files = {}
self.filenames = watch_files
self.call_func_on_change = call_func_on_change
self.args = args
self.kwargs = kwargs
# Look for changes
def look(self):
for file in self.filenames:
stamp = os.stat(file).st_mtime
if not file in self._cached_stamp_files:
self._cached_stamp_files[file] = 0
if stamp != self._cached_stamp_files[file]:
self._cached_stamp_files[file] = stamp
# File has changed, so do something...
file_to_read = open(file, 'r')
value = file_to_read.read()
print("value from file", value)
file_to_read.seek(0)
if self.call_func_on_change is not None:
self.call_func_on_change(*self.args, **self.kwargs)
# Keep watching in a loop
def watch(self):
while self.running:
try:
# Look for changes
time.sleep(self.refresh_delay_secs)
self.look()
except KeyboardInterrupt:
print('\nDone')
break
except FileNotFoundError:
# Action on file not found
pass
except Exception as e:
print(e)
print('Unhandled error: %s' % sys.exc_info()[0])
# Call this function each time a change happens
def custom_action(text):
print(text)
# pass
watch_files = ['/Users/mexekanez/my_file.txt', '/Users/mexekanez/my_file1.txt']
# watcher = Watcher(watch_file) # simple
if __name__ == "__main__":
watcher = Watcher(watch_files, custom_action, text='yes, changed') # also call custom action function
watcher.watch() # start the watch going
The best and simplest solution is to use pygtail:
https://pypi.python.org/pypi/pygtail
from pygtail import Pygtail
import sys
while True:
for line in Pygtail("some.log"):
sys.stdout.write(line)
import inotify.adapters
from datetime import datetime
LOG_FILE='/var/log/mysql/server_audit.log'
def main():
start_time = datetime.now()
while True:
i = inotify.adapters.Inotify()
i.add_watch(LOG_FILE)
for event in i.event_gen(yield_nones=False):
break
del i
with open(LOG_FILE, 'r') as f:
for line in f:
entry = line.split(',')
entry_time = datetime.strptime(entry[0],
'%Y%m%d %H:%M:%S')
if entry_time > start_time:
start_time = entry_time
print(entry)
if __name__ == '__main__':
main()
The easiest solution would get the two instances of the same file after an interval and Compare them. You Could try something like this
while True:
# Capturing the two instances models.py after certain interval of time
print("Looking for changes in " + app_name.capitalize() + " models.py\nPress 'CTRL + C' to stop the program")
with open(app_name.capitalize() + '/filename', 'r+') as app_models_file:
filename_content = app_models_file.read()
time.sleep(5)
with open(app_name.capitalize() + '/filename', 'r+') as app_models_file_1:
filename_content_1 = app_models_file_1.read()
# Comparing models.py after certain interval of time
if filename_content == filename_content_1:
pass
else:
print("You made a change in " + app_name.capitalize() + " filename.\n")
cmd = str(input("Do something with the file?(y/n):"))
if cmd == 'y':
# Do Something
elif cmd == 'n':
# pass or do something
else:
print("Invalid input")
If you're using windows, create this POLL.CMD file
#echo off
:top
xcopy /m /y %1 %2 | find /v "File(s) copied"
timeout /T 1 > nul
goto :top
then you can type "poll dir1 dir2" and it will copy all the files from dir1 to dir2 and check for updates once per second.
The "find" is optional, just to make the console less noisy.
This is not recursive. Maybe you could make it recursive using /e on the xcopy.
I don't know any Windows specific function. You could try getting the MD5 hash of the file every second/minute/hour (depends on how fast you need it) and compare it to the last hash. When it differs you know the file has been changed and you read out the newest lines.
I'd try something like this.
try:
f = open(filePath)
except IOError:
print "No such file: %s" % filePath
raw_input("Press Enter to close window")
try:
lines = f.readlines()
while True:
line = f.readline()
try:
if not line:
time.sleep(1)
else:
functionThatAnalisesTheLine(line)
except Exception, e:
# handle the exception somehow (for example, log the trace) and raise the same exception again
raw_input("Press Enter to close window")
raise e
finally:
f.close()
The loop checks if there is a new line(s) since last time file was read - if there is, it's read and passed to the functionThatAnalisesTheLine function. If not, script waits 1 second and retries the process.
I have a setup.py script which needs to probe the compiler for certain things like the support for TR1, the presence of windows.h (to add NOMINMAX define), etc. I do these checks by creating a simple program and trying to compile it with Distutils' Compiler class. The presence/lack of errors is my answer.
This works well, but it means that the compiler's ugly error messages get printed to the console. Is there a way to suppress error messages for when the compile function is called manually?
Here is my function which tries to compile the program, which now DOES eliminate the error messages by piping the error stream to a file (answered my own question):
def see_if_compiles(program, include_dirs, define_macros):
""" Try to compile the passed in program and report if it compiles successfully or not. """
from distutils.ccompiler import new_compiler, CompileError
from shutil import rmtree
import tempfile
import os
try:
tmpdir = tempfile.mkdtemp()
except AttributeError:
# Python 2.2 doesn't have mkdtemp().
tmpdir = "compile_check_tempdir"
try:
os.mkdir(tmpdir)
except OSError:
print "Can't create temporary directory. Aborting."
sys.exit()
old = os.getcwd()
os.chdir(tmpdir)
# Write the program
f = open('compiletest.cpp', 'w')
f.write(program)
f.close()
# redirect the error stream to keep ugly compiler error messages off the command line
devnull = open('errors.txt', 'w')
oldstderr = os.dup(sys.stderr.fileno())
os.dup2(devnull.fileno(), sys.stderr.fileno())
#
try:
c = new_compiler()
for macro in define_macros:
c.define_macro(name=macro[0], value=macro[1])
c.compile([f.name], include_dirs=include_dirs)
success = True
except CompileError:
success = False
# undo the error stream redirect
os.dup2(oldstderr, sys.stderr.fileno())
devnull.close()
os.chdir(old)
rmtree(tmpdir)
return success
Here is a function which uses the above to check for the presence of a header.
def check_for_header(header, include_dirs, define_macros):
"""Check for the existence of a header file by creating a small program which includes it and see if it compiles."""
program = "#include <%s>\n" % header
sys.stdout.write("Checking for <%s>... " % header)
success = see_if_compiles(program, include_dirs, define_macros)
if (success):
sys.stdout.write("OK\n");
else:
sys.stdout.write("Not found\n");
return success
Zac's comment spurred me to look a bit more and I found that Mercurial's setup.py script has a working method for his approach. You can't just assign the stream because the change won't get inherited by the compiler process, but apparently Python has our good friend dup2() in the form of os.dup2(). That allows the same OS-level stream shenanigans that we all know and love, which do get inherited to child processes.
Mercurial's function redirects to /dev/null, but to keep Windows compatibility I just redirect to a file then delete it.
Quoth Mercurial:
# simplified version of distutils.ccompiler.CCompiler.has_function
# that actually removes its temporary files.
def hasfunction(cc, funcname):
tmpdir = tempfile.mkdtemp(prefix='hg-install-')
devnull = oldstderr = None
try:
try:
fname = os.path.join(tmpdir, 'funcname.c')
f = open(fname, 'w')
f.write('int main(void) {\n')
f.write(' %s();\n' % funcname)
f.write('}\n')
f.close()
# Redirect stderr to /dev/null to hide any error messages
# from the compiler.
# This will have to be changed if we ever have to check
# for a function on Windows.
devnull = open('/dev/null', 'w')
oldstderr = os.dup(sys.stderr.fileno())
os.dup2(devnull.fileno(), sys.stderr.fileno())
objects = cc.compile([fname], output_dir=tmpdir)
cc.link_executable(objects, os.path.join(tmpdir, "a.out"))
except:
return False
return True
finally:
if oldstderr is not None:
os.dup2(oldstderr, sys.stderr.fileno())
if devnull is not None:
devnull.close()
shutil.rmtree(tmpdir)
Here's a context manager that I recently wrote and found useful, because I was having the same problem with distutils.ccompiler.CCompiler.has_function while working on pymssql. I was going to use your approach (nice, thanks for sharing!) but then I thought that it could be done with less code and would be more general and flexible if I used a context manager. Here's what I came up with:
import contextlib
#contextlib.contextmanager
def stdchannel_redirected(stdchannel, dest_filename):
"""
A context manager to temporarily redirect stdout or stderr
e.g.:
with stdchannel_redirected(sys.stderr, os.devnull):
if compiler.has_function('clock_gettime', libraries=['rt']):
libraries.append('rt')
"""
try:
oldstdchannel = os.dup(stdchannel.fileno())
dest_file = open(dest_filename, 'w')
os.dup2(dest_file.fileno(), stdchannel.fileno())
yield
finally:
if oldstdchannel is not None:
os.dup2(oldstdchannel, stdchannel.fileno())
if dest_file is not None:
dest_file.close()
The context for why I created this is at this blog post. Pretty much the same as yours I think.
This uses code that I borrowed from you to do the redirection (e.g.: os.dup2, etc.), but I wrapped it in a context manager so it's more general and reusable.
I use it like this in a setup.py:
with stdchannel_redirected(sys.stderr, os.devnull):
if compiler.has_function('clock_gettime', libraries=['rt']):
libraries.append('rt')
#Adam I just want to point out that there is /dev/null equivalent on Windows. It's 'NUL' but good practice is to get it from os.devnull
I'm pretty new to programming and python, so disregard this if it's a stupid suggestion, but can't you just reroute the error messages to a text file instead of the screen/interactive window/whatever?
I'm pretty sure I read somewhere you can do something like
error = open('yourerrorlog.txt','w')
sys.stderr = error
Again, sorry I'm probably repeating something you already know, but if the problem is you WANT the errors when it's called by another function (automated) and no errors when it's ran manual, can't you just add a keyword argument like compile(arg1, arg2, manual=True ) and then under your "except:" you add
if manual == False: print errors to console/interactive window
else: print to error
Then when it's called by the program and not manually you just call it with compile(arg1,arg2, manual=False) so that it redirects to the file.
Does running in quiet mode help at all? setup.py -q build
Not a direct answer to your question, but related to your use case: there is a config command in distutils that’s designed to be subclassed and used to check for C features. It’s not documented yet, you have to read the source.
I have a log file being written by another process which I want to watch for changes. Each time a change occurs I'd like to read the new data in to do some processing on it.
What's the best way to do this? I was hoping there'd be some sort of hook from the PyWin32 library. I've found the win32file.FindNextChangeNotification function but have no idea how to ask it to watch a specific file.
If anyone's done anything like this I'd be really grateful to hear how...
[Edit] I should have mentioned that I was after a solution that doesn't require polling.
[Edit] Curses! It seems this doesn't work over a mapped network drive. I'm guessing windows doesn't 'hear' any updates to the file the way it does on a local disk.
Did you try using Watchdog?
Python API library and shell utilities to monitor file system events.
Directory monitoring made easy with
A cross-platform API.
A shell tool to run commands in response to directory changes.
Get started quickly with a simple example in Quickstart...
If polling is good enough for you, I'd just watch if the "modified time" file stat changes. To read it:
os.stat(filename).st_mtime
(Also note that the Windows native change event solution does not work in all circumstances, e.g. on network drives.)
import os
class Monkey(object):
def __init__(self):
self._cached_stamp = 0
self.filename = '/path/to/file'
def ook(self):
stamp = os.stat(self.filename).st_mtime
if stamp != self._cached_stamp:
self._cached_stamp = stamp
# File has changed, so do something...
If you want a multiplatform solution, then check QFileSystemWatcher.
Here an example code (not sanitized):
from PyQt4 import QtCore
#QtCore.pyqtSlot(str)
def directory_changed(path):
print('Directory Changed!!!')
#QtCore.pyqtSlot(str)
def file_changed(path):
print('File Changed!!!')
fs_watcher = QtCore.QFileSystemWatcher(['/path/to/files_1', '/path/to/files_2', '/path/to/files_3'])
fs_watcher.connect(fs_watcher, QtCore.SIGNAL('directoryChanged(QString)'), directory_changed)
fs_watcher.connect(fs_watcher, QtCore.SIGNAL('fileChanged(QString)'), file_changed)
It should not work on windows (maybe with cygwin ?), but for unix user, you should use the "fcntl" system call. Here is an example in Python. It's mostly the same code if you need to write it in C (same function names)
import time
import fcntl
import os
import signal
FNAME = "/HOME/TOTO/FILETOWATCH"
def handler(signum, frame):
print "File %s modified" % (FNAME,)
signal.signal(signal.SIGIO, handler)
fd = os.open(FNAME, os.O_RDONLY)
fcntl.fcntl(fd, fcntl.F_SETSIG, 0)
fcntl.fcntl(fd, fcntl.F_NOTIFY,
fcntl.DN_MODIFY | fcntl.DN_CREATE | fcntl.DN_MULTISHOT)
while True:
time.sleep(10000)
Check out pyinotify.
inotify replaces dnotify (from an earlier answer) in newer linuxes and allows file-level rather than directory-level monitoring.
For watching a single file with polling, and minimal dependencies, here is a fully fleshed-out example, based on answer from Deestan (above):
import os
import sys
import time
class Watcher(object):
running = True
refresh_delay_secs = 1
# Constructor
def __init__(self, watch_file, call_func_on_change=None, *args, **kwargs):
self._cached_stamp = 0
self.filename = watch_file
self.call_func_on_change = call_func_on_change
self.args = args
self.kwargs = kwargs
# Look for changes
def look(self):
stamp = os.stat(self.filename).st_mtime
if stamp != self._cached_stamp:
self._cached_stamp = stamp
# File has changed, so do something...
print('File changed')
if self.call_func_on_change is not None:
self.call_func_on_change(*self.args, **self.kwargs)
# Keep watching in a loop
def watch(self):
while self.running:
try:
# Look for changes
time.sleep(self.refresh_delay_secs)
self.look()
except KeyboardInterrupt:
print('\nDone')
break
except FileNotFoundError:
# Action on file not found
pass
except:
print('Unhandled error: %s' % sys.exc_info()[0])
# Call this function each time a change happens
def custom_action(text):
print(text)
watch_file = 'my_file.txt'
# watcher = Watcher(watch_file) # simple
watcher = Watcher(watch_file, custom_action, text='yes, changed') # also call custom action function
watcher.watch() # start the watch going
Well after a bit of hacking of Tim Golden's script, I have the following which seems to work quite well:
import os
import win32file
import win32con
path_to_watch = "." # look at the current directory
file_to_watch = "test.txt" # look for changes to a file called test.txt
def ProcessNewData( newData ):
print "Text added: %s"%newData
# Set up the bits we'll need for output
ACTIONS = {
1 : "Created",
2 : "Deleted",
3 : "Updated",
4 : "Renamed from something",
5 : "Renamed to something"
}
FILE_LIST_DIRECTORY = 0x0001
hDir = win32file.CreateFile (
path_to_watch,
FILE_LIST_DIRECTORY,
win32con.FILE_SHARE_READ | win32con.FILE_SHARE_WRITE,
None,
win32con.OPEN_EXISTING,
win32con.FILE_FLAG_BACKUP_SEMANTICS,
None
)
# Open the file we're interested in
a = open(file_to_watch, "r")
# Throw away any exising log data
a.read()
# Wait for new data and call ProcessNewData for each new chunk that's written
while 1:
# Wait for a change to occur
results = win32file.ReadDirectoryChangesW (
hDir,
1024,
False,
win32con.FILE_NOTIFY_CHANGE_LAST_WRITE,
None,
None
)
# For each change, check to see if it's updating the file we're interested in
for action, file in results:
full_filename = os.path.join (path_to_watch, file)
#print file, ACTIONS.get (action, "Unknown")
if file == file_to_watch:
newText = a.read()
if newText != "":
ProcessNewData( newText )
It could probably do with a load more error checking, but for simply watching a log file and doing some processing on it before spitting it out to the screen, this works well.
Thanks everyone for your input - great stuff!
Check my answer to a similar question. You could try the same loop in Python. This page suggests:
import time
while 1:
where = file.tell()
line = file.readline()
if not line:
time.sleep(1)
file.seek(where)
else:
print line, # already has newline
Also see the question tail() a file with Python.
This is another modification of Tim Goldan's script that runs on unix types and adds a simple watcher for file modification by using a dict (file=>time).
usage: whateverName.py path_to_dir_to_watch
#!/usr/bin/env python
import os, sys, time
def files_to_timestamp(path):
files = [os.path.join(path, f) for f in os.listdir(path)]
return dict ([(f, os.path.getmtime(f)) for f in files])
if __name__ == "__main__":
path_to_watch = sys.argv[1]
print('Watching {}..'.format(path_to_watch))
before = files_to_timestamp(path_to_watch)
while 1:
time.sleep (2)
after = files_to_timestamp(path_to_watch)
added = [f for f in after.keys() if not f in before.keys()]
removed = [f for f in before.keys() if not f in after.keys()]
modified = []
for f in before.keys():
if not f in removed:
if os.path.getmtime(f) != before.get(f):
modified.append(f)
if added: print('Added: {}'.format(', '.join(added)))
if removed: print('Removed: {}'.format(', '.join(removed)))
if modified: print('Modified: {}'.format(', '.join(modified)))
before = after
Here is a simplified version of Kender's code that appears to do the same trick and does not import the entire file:
# Check file for new data.
import time
f = open(r'c:\temp\test.txt', 'r')
while True:
line = f.readline()
if not line:
time.sleep(1)
print 'Nothing New'
else:
print 'Call Function: ', line
Well, since you are using Python, you can just open a file and keep reading lines from it.
f = open('file.log')
If the line read is not empty, you process it.
line = f.readline()
if line:
// Do what you want with the line
You may be missing that it is ok to keep calling readline at the EOF. It will just keep returning an empty string in this case. And when something is appended to the log file, the reading will continue from where it stopped, as you need.
If you are looking for a solution that uses events, or a particular library, please specify this in your question. Otherwise, I think this solution is just fine.
Simplest solution for me is using watchdog's tool watchmedo
From https://pypi.python.org/pypi/watchdog I now have a process that looks up the sql files in a directory and executes them if necessary.
watchmedo shell-command \
--patterns="*.sql" \
--recursive \
--command='~/Desktop/load_files_into_mysql_database.sh' \
.
As you can see in Tim Golden's article, pointed by Horst Gutmann, WIN32 is relatively complex and watches directories, not a single file.
I'd like to suggest you look into IronPython, which is a .NET python implementation.
With IronPython you can use all the .NET functionality - including
System.IO.FileSystemWatcher
Which handles single files with a simple Event interface.
This is an example of checking a file for changes. One that may not be the best way of doing it, but it sure is a short way.
Handy tool for restarting application when changes have been made to the source. I made this when playing with pygame so I can see effects take place immediately after file save.
When used in pygame make sure the stuff in the 'while' loop is placed in your game loop aka update or whatever. Otherwise your application will get stuck in an infinite loop and you will not see your game updating.
file_size_stored = os.stat('neuron.py').st_size
while True:
try:
file_size_current = os.stat('neuron.py').st_size
if file_size_stored != file_size_current:
restart_program()
except:
pass
In case you wanted the restart code which I found on the web. Here it is. (Not relevant to the question, though it could come in handy)
def restart_program(): #restart application
python = sys.executable
os.execl(python, python, * sys.argv)
Have fun making electrons do what you want them to do.
Seems that no one has posted fswatch. It is a cross-platform file system watcher. Just install it, run it and follow the prompts.
I've used it with python and golang programs and it just works.
ACTIONS = {
1 : "Created",
2 : "Deleted",
3 : "Updated",
4 : "Renamed from something",
5 : "Renamed to something"
}
FILE_LIST_DIRECTORY = 0x0001
class myThread (threading.Thread):
def __init__(self, threadID, fileName, directory, origin):
threading.Thread.__init__(self)
self.threadID = threadID
self.fileName = fileName
self.daemon = True
self.dir = directory
self.originalFile = origin
def run(self):
startMonitor(self.fileName, self.dir, self.originalFile)
def startMonitor(fileMonitoring,dirPath,originalFile):
hDir = win32file.CreateFile (
dirPath,
FILE_LIST_DIRECTORY,
win32con.FILE_SHARE_READ | win32con.FILE_SHARE_WRITE,
None,
win32con.OPEN_EXISTING,
win32con.FILE_FLAG_BACKUP_SEMANTICS,
None
)
# Wait for new data and call ProcessNewData for each new chunk that's
# written
while 1:
# Wait for a change to occur
results = win32file.ReadDirectoryChangesW (
hDir,
1024,
False,
win32con.FILE_NOTIFY_CHANGE_LAST_WRITE,
None,
None
)
# For each change, check to see if it's updating the file we're
# interested in
for action, file_M in results:
full_filename = os.path.join (dirPath, file_M)
#print file, ACTIONS.get (action, "Unknown")
if len(full_filename) == len(fileMonitoring) and action == 3:
#copy to main file
...
Since I have it installed globally, my favorite approach is to use nodemon. If your source code is in src, and your entry point is src/app.py, then it's as easy as:
nodemon -w 'src/**' -e py,html --exec python src/app.py
... where -e py,html lets you control what file types to watch for changes.
Here's an example geared toward watching input files that write no more than one line per second but usually a lot less. The goal is to append the last line (most recent write) to the specified output file. I've copied this from one of my projects and just deleted all the irrelevant lines. You'll have to fill in or change the missing symbols.
from PyQt5.QtCore import QFileSystemWatcher, QSettings, QThread
from ui_main_window import Ui_MainWindow # Qt Creator gen'd
class MainWindow(QMainWindow, Ui_MainWindow):
def __init__(self, parent=None):
QMainWindow.__init__(self, parent)
Ui_MainWindow.__init__(self)
self._fileWatcher = QFileSystemWatcher()
self._fileWatcher.fileChanged.connect(self.fileChanged)
def fileChanged(self, filepath):
QThread.msleep(300) # Reqd on some machines, give chance for write to complete
# ^^ About to test this, may need more sophisticated solution
with open(filepath) as file:
lastLine = list(file)[-1]
destPath = self._filemap[filepath]['dest file']
with open(destPath, 'a') as out_file: # a= append
out_file.writelines([lastLine])
Of course, the encompassing QMainWindow class is not strictly required, ie. you can use QFileSystemWatcher alone.
Just to put this out there since no one mentioned it: there's a Python module in the Standard Library named filecmp which has this cmp() function that compares two files.
Just make sure you don't do from filecmp import cmp to not overshadow the built-in cmp() function in Python 2.x. That's okay in Python 3.x, though, since there's no such built-in cmp() function anymore.
Anyway, this is how its use looks like:
import filecmp
filecmp.cmp(path_to_file_1, path_to_file_2, shallow=True)
The argument shallow defaults to True. If the argument's value is True, then only the metadata of the files are compared; however, if the argument's value is False, then the contents of the files are compared.
Maybe this information will be useful to someone.
watchfiles (https://github.com/samuelcolvin/watchfiles) is a Python API and CLI that uses the Notify (https://github.com/notify-rs/notify) library written in Rust.
The rust implementation currently (2022-10-09) supports:
Linux / Android: inotify
macOS: FSEvents or kqueue, see features
Windows: ReadDirectoryChangesW
FreeBSD / NetBSD / OpenBSD / DragonflyBSD: kqueue
All platforms: polling
Binaries available on PyPI (https://pypi.org/project/watchfiles/) and conda-forge (https://github.com/conda-forge/watchfiles-feedstock).
You can also use a simple library called repyt, here is an example:
repyt ./app.py
related #4Oh4 solution a smooth change for a list of files to watch;
import os
import sys
import time
class Watcher(object):
running = True
refresh_delay_secs = 1
# Constructor
def __init__(self, watch_files, call_func_on_change=None, *args, **kwargs):
self._cached_stamp = 0
self._cached_stamp_files = {}
self.filenames = watch_files
self.call_func_on_change = call_func_on_change
self.args = args
self.kwargs = kwargs
# Look for changes
def look(self):
for file in self.filenames:
stamp = os.stat(file).st_mtime
if not file in self._cached_stamp_files:
self._cached_stamp_files[file] = 0
if stamp != self._cached_stamp_files[file]:
self._cached_stamp_files[file] = stamp
# File has changed, so do something...
file_to_read = open(file, 'r')
value = file_to_read.read()
print("value from file", value)
file_to_read.seek(0)
if self.call_func_on_change is not None:
self.call_func_on_change(*self.args, **self.kwargs)
# Keep watching in a loop
def watch(self):
while self.running:
try:
# Look for changes
time.sleep(self.refresh_delay_secs)
self.look()
except KeyboardInterrupt:
print('\nDone')
break
except FileNotFoundError:
# Action on file not found
pass
except Exception as e:
print(e)
print('Unhandled error: %s' % sys.exc_info()[0])
# Call this function each time a change happens
def custom_action(text):
print(text)
# pass
watch_files = ['/Users/mexekanez/my_file.txt', '/Users/mexekanez/my_file1.txt']
# watcher = Watcher(watch_file) # simple
if __name__ == "__main__":
watcher = Watcher(watch_files, custom_action, text='yes, changed') # also call custom action function
watcher.watch() # start the watch going
The best and simplest solution is to use pygtail:
https://pypi.python.org/pypi/pygtail
from pygtail import Pygtail
import sys
while True:
for line in Pygtail("some.log"):
sys.stdout.write(line)
import inotify.adapters
from datetime import datetime
LOG_FILE='/var/log/mysql/server_audit.log'
def main():
start_time = datetime.now()
while True:
i = inotify.adapters.Inotify()
i.add_watch(LOG_FILE)
for event in i.event_gen(yield_nones=False):
break
del i
with open(LOG_FILE, 'r') as f:
for line in f:
entry = line.split(',')
entry_time = datetime.strptime(entry[0],
'%Y%m%d %H:%M:%S')
if entry_time > start_time:
start_time = entry_time
print(entry)
if __name__ == '__main__':
main()
The easiest solution would get the two instances of the same file after an interval and Compare them. You Could try something like this
while True:
# Capturing the two instances models.py after certain interval of time
print("Looking for changes in " + app_name.capitalize() + " models.py\nPress 'CTRL + C' to stop the program")
with open(app_name.capitalize() + '/filename', 'r+') as app_models_file:
filename_content = app_models_file.read()
time.sleep(5)
with open(app_name.capitalize() + '/filename', 'r+') as app_models_file_1:
filename_content_1 = app_models_file_1.read()
# Comparing models.py after certain interval of time
if filename_content == filename_content_1:
pass
else:
print("You made a change in " + app_name.capitalize() + " filename.\n")
cmd = str(input("Do something with the file?(y/n):"))
if cmd == 'y':
# Do Something
elif cmd == 'n':
# pass or do something
else:
print("Invalid input")
If you're using windows, create this POLL.CMD file
#echo off
:top
xcopy /m /y %1 %2 | find /v "File(s) copied"
timeout /T 1 > nul
goto :top
then you can type "poll dir1 dir2" and it will copy all the files from dir1 to dir2 and check for updates once per second.
The "find" is optional, just to make the console less noisy.
This is not recursive. Maybe you could make it recursive using /e on the xcopy.
I don't know any Windows specific function. You could try getting the MD5 hash of the file every second/minute/hour (depends on how fast you need it) and compare it to the last hash. When it differs you know the file has been changed and you read out the newest lines.
I'd try something like this.
try:
f = open(filePath)
except IOError:
print "No such file: %s" % filePath
raw_input("Press Enter to close window")
try:
lines = f.readlines()
while True:
line = f.readline()
try:
if not line:
time.sleep(1)
else:
functionThatAnalisesTheLine(line)
except Exception, e:
# handle the exception somehow (for example, log the trace) and raise the same exception again
raw_input("Press Enter to close window")
raise e
finally:
f.close()
The loop checks if there is a new line(s) since last time file was read - if there is, it's read and passed to the functionThatAnalisesTheLine function. If not, script waits 1 second and retries the process.