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How should i pass username and password to Cassandra using python script

I am new to python programming, I am trying to build a script that will take Casandra metadata backup.
My script is working fine when there is authentication configured in yaml file but it failed when we turned on authentication.
This is the part where I am calling CQLSH.
with open(save_path + '/' + filename, 'w') as f:
query_process = subprocess.Popen(['echo', query], stdout=subprocess.PIPE)
cqlsh = subprocess.Popen(('/bin/cqlsh', host),
stdin=query_process.stdout, stdout=f)
query_process.stdout.close()
return (save_path + filename)
It will be really helpful for me if anyone can help.

Depending on your configuration and deployment there are a couple of options.
You might just choose to pass them as command line options to your popen command.
Another alternative is to have them in a cqlshrc file, which is either read from the standard location (~/.cassandra/cqlshrc), or an alternative path passed as another command line option.

python script using subprocess, redirect ALL output to file

I am writing something for static analysis of source code in different languages. As anything has to be open source and callable from command line I now have downloaded one tool per language. So I decided to write a python script listing all source files in a project folder and calling the respective tool.
So part of my code looks like this:
import os
import sys
import subprocess
from subprocess import call
from pylint.lint import Run as pylint
class Analyser:
def __init__(self, source=os.getcwd(), logfilename=None):
# doing initialization stuff
self.logfilename = logfilename or 'CodeAnalysisReport.log'
self.listFiles()
self.analyseFiles()
def listFiles(self):
# lists all source files in the specified directory
def analyseFiles(self):
self.analysePythons()
self.analyseCpps()
self.analyseJss()
self.analyseJavas()
self.analyseCs()
if __name__ == '__main__':
Analyser()
Let's have at a look at the C++ files part (I use Cppcheck to analyse those):
def analyseCpps(self):
for sourcefile in self.files['.cc'] + self.files['.cpp']:
print '\n'*2, '*'*70, '\n', sourcefile
call(['C:\\CodeAnalysis\\cppcheck\\cppcheck', '--enable=all', sourcefile])
The console output for one of the files (it's just a random downloaded file) is:
**********************************************************************
C:\CodeAnalysis\testproject\cpp\BiggestUnInt.cc
Checking C:\CodeAnalysis\testproject\cpp\BiggestUnInt.cc...
[C:\CodeAnalysis\testproject\cpp\BiggestUnInt.cc:18]: (style) The scope of the variable 'oldi' can be reduced.
[C:\CodeAnalysis\testproject\cpp\BiggestUnInt.cc:43]: (style) The scope of the variable 'lastbit' can be reduced.
[C:\CodeAnalysis\testproject\cpp\BiggestUnInt.cc:44]: (style) The scope of the variable 'two_to_power_i' can be reduced.
(information) Cppcheck cannot find all the include files (use --check-config for details)
Line 1 and 2 coming from my script, lines 3 to 7 coming from Cppcheck.
And this is what I want to save to my log file, for all the other files too. Everything in one single file.
Of course I have searched SO and found some methods. But none is working completely.
First try:
Adding sys.stdout = open(self.logfilename, 'w') to my constructor. This makes line 1 and 2 of the above showed output be written to my log file. The rest is still shown on console.
Second try:
Additionaly, in analyseCpps I use:
call(['C:\CodeAnalysis\cppcheck\cppcheck', '--enable=all', sourcefile], stdout=sys.stdout)
This makes my log file to be:
Checking C:\CodeAnalysis\testproject\cpp\BiggestUnInt.cc...
**********************************************************************
C:\CodeAnalysis\testproject\cpp\BiggestUnInt.cc
and the console output is:
[C:\CodeAnalysis\testproject\cpp\BiggestUnInt.cc:18]: (style) The scope of the variable 'oldi' can be reduced.
[C:\CodeAnalysis\testproject\cpp\BiggestUnInt.cc:43]: (style) The scope of the variable 'lastbit' can be reduced.
[C:\CodeAnalysis\testproject\cpp\BiggestUnInt.cc:44]: (style) The scope of the variable 'two_to_power_i' can be reduced.
Not what I want.
Third try:
Using Popen with pipe. sys.stdout is back to default.
As preliminary work analyseCpps now is:
for sourcefile in self.files['.cc'] + self.files['.cpp']:
print '\n'*2, '*'*70, '\n', sourcefile
p = subprocess.Popen(['C:\\CodeAnalysis\\cppcheck\\cppcheck', '--enable=all', sourcefile], stdout=subprocess.PIPE)
p.stdout.read()
p.stdout.read() shows only the last line of my desired output (line 7 in code box 3)
Fourth try:
Using subprocess.Popen(['C:\CodeAnalysis\cppcheck\cppcheck', '--enable=all', sourcefile], stdout=open(self.logfilename, 'a+')) just writes the one line Checking C:\CodeAnalysis\testproject\cpp\BiggestUnInt.cc... to my logfile, the rest is shown on the console.
Fifth try:
Instead of subprocess.Popen I use os.system, so my calling command is:
os.system('C:\CodeAnalysis\cppcheck\cppcheck --enable=all %s >> %s' % (sourcefile, self.logfilename))
This results in the same log file as my fourth try. If I type the same command directly in the windows console the result is the same. So I guess it it is not exactly a python problem but still:
If it is on the console there must be a way to put it in a file. Any ideas?
E D I T
Foolish me. I'm still a noob so I forgot about the stderr. That's where the decisive messages are going to.
So now I have:
def analyseCpps(self):
for sourcefile in self.files['.cc'] + self.files['.cpp']:
p = subprocess.Popen(['C:\\CodeAnalysis\\cppcheck\\cppcheck', '--enable=all', sourcefile], stderr=subprocess.PIPE)
with open(self.logfilename, 'a+') as logfile:
logfile.write('%s\n%s\n' % ('*'*70, sourcefile))
for line in p.stderr.readlines():
logfile.write('%s\n' % line.strip())
and it's working fine.
ANOTHER EDIT
according to Didier's answer:
with sys.stdout = open(self.logfilename, 'w', 0) in my constructor:
def analyseCpps(self):
for sourcefile in self.files['.cc'] + self.files['.cpp']:
print '\n'*2, '*'*70, '\n', sourcefile
p = subprocess.Popen(['C:\\CodeAnalysis\\cppcheck\\cppcheck', '--enable=all', sourcefile], stdout=sys.stdout, stderr=sys.stdout)

There are several problems:
you should redirect both stdout and stderr
you should use unbuffered files if you want to mix normal print and the output of launched commands.
Something like this:
import sys, subprocess
# Note the 0 here (unbuffered file)
sys.stdout = open("mylog","w",0)
print "Hello"
print "-----"
subprocess.call(["./prog"],stdout=sys.stdout, stderr=sys.stdout)
print "-----"
subprocess.call(["./prog"],stdout=sys.stdout, stderr=sys.stdout)
print "-----"
print "End"

You need to redirect stderr too, you can use STDOUT or pass the file object to stderr=:
from subprocess import check_call,STDOUT
with open("log.txt","w") as f:
for sourcefile in self.files['.cc'] + self.files['.cpp']:
check_call(['C:\\CodeAnalysis\\cppcheck\\cppcheck', '--enable=all', sourcefile],
stdout=f, stderr=STDOUT)

Try to redirect stdout and stderr to a logfile:
import subprocess
def analyseCpps(self):
with open("logfile.txt", "w") as logfile:
for sourcefile in self.files['.cc'] + self.files['.cpp']:
print '\n'*2, '*'*70, '\n', sourcefile
call(['C:\\CodeAnalysis\\cppcheck\\cppcheck',
'--enable=all', sourcefile], stdout=logfile,
stderr=subprocess.STDOUT)
In this example the filename is hardcoded, but you should be able to change that easily (to your self.logfilename or similar).

Django Subprocess live/unbuffered reporting of stdout from batch scripts

Basically the back story is that i've built a selecting of python scripts for a client to process importing and exporting batch jobs between their operations database and their ecomms site database. this works fine. these scripts write to stdout to update the user on the status of the batch script.
I'm trying to produce a framework for these scripts to be run via a django view and to post the stdout to the webpage to show the user the progress of these batch processes.
the plan was to
- call the batch script as a subprocess and then save stdout and stderr to a file.
- return a redirect to a display page that will reload every 2 seconds and display line by line the contents of the file that stdout is being written to.
however the problem is, that the stdout/stderr file is not being actually written to until the entire batch script has finished running or errors out.
i've tried a number of things, but none seem to work.
heres the current view code.
def long_running(app, filename):
"""where app is ['command', 'arg1', 'arg2'] and filename is the file used for output"""
# where to write the result (something like /tmp/some-unique-id)
fullname = temppath+filename
f = file(fullname, "a+")
# launch the script which outputs something slowly
subprocess.Popen(app, stdout=f, stderr=f)# .communicate()
# once the script is done, close the output
f.close()
def attributeexport(request):
filename = "%d_attribute" %(int(time.time())) #set the filename to be the current time stamp plus an identifier
app = ['python','/home/windsor/django/applications/attribute_exports.py']
#break thread for processing.
threading.Thread(target=long_running, args=(app,filename)).start()
return HttpResponseRedirect('/scripts/dynamic/'+filename+'/')
pass
def dynamic(request, viewfile):
fileobj = open(temppath+viewfile, 'r')
results = []
for line in fileobj:
results.append(line)
if '~END' in line:
#if the process has completed
return render_to_response('scripts/static.html', {'displaylist':results, 'filename':viewfile})
return render_to_response('scripts/dynamic.html', {'displaylist':results, 'filename':viewfile})
pass

It helps if you use the following:
['python','-u','path/to/python/script.py']

Python, redirecting the stream of Popen to a python function

I'm new to python programming.
I have this problem: I have a list of text files (both compressed and not) and I need to :
- connect to the server and open them
- after the opening of the file, I need to take his content and pass it to another python function that I wrote
def readLogs (fileName):
f = open (fileName, 'r')
inStream = f.read()
counter = 0
inStream = re.split('\n', inStream) # Create a 'list of lines'
out = "" # Will contain the output
logInConst = "" # log In Construction
curLine = "" # Line that I am working on
for nextLine in inStream:
logInConst += curLine
curLine = nextLine
# check if it is a start of a new log && check if the previous log is 'ready'
if newLogRegExp.match(curLine) and logInConst != "":
counter = counter + 1
out = logInConst
logInConst = ""
yield out
yield logInConst + curLine
def checkFile (regExp, fileName):
generatore = readLogs(fileName)
listOfMatches=[]
for i in generatore: #I'm now cycling through the logs
# regExp must be a COMPILE regular expression
if regExp.search(i):
listOfMatches.append(i)
return listOfMatches
in order to elaborate the info contained in those files.
The function has the aim of write in just 1 line the logs that are stored in those files using 3 lines ... The function is working fine on files read from my local machine but I cannot figure out how to connect to a remote server and create these one-line logs without storing the content of each file into a string and then working with the string ... The command that I use to connect to the remote machine is :
connection_out = Popen(['ssh', retList[0], 'cd '+retList[2]+'; cat'+fileName], stdout=PIPE).communicate()[0]
retList[0] and retList[2] are the user#remote and the folder name that I have to access
Thanks to all in advance !
UPDATE:
My problem is that I have to establish an ssh connection first :
pr1=Popen(['ssh', 'siatc#lgssp101', '*~/XYZ/AAAAA/log_archive/00/MSG_090308_162648.gz*' ], stdout=PIPE).communicate()[0]
All the files that I need to open are stored in a list, fileList[], part of them are compressed (.gz) and part are just text files !! I have tried all the procedures that u showed before bot nothing worked ... I think that I mus modify the third argument of the Popen function but I cannot figure out how to do it ! Is there anyone that can help me ???

You do not have to split the stream/file into lines yourself. Just iterate:
for ln in f:
# work on line in ln
This should work equally well for files (using open() for file()) and pipes (using Popen). Use the stdout property of the popen object to access the pipe connected to stdout of the subprocess
Example
from subprocess import Popen, PIPE
pp = Popen('dir', shell=True, stdout=PIPE)
for ln in pp.stdout:
print '#',ln

Remove InStream and just use the file object.
So that your code would read:
for nextLine in f.readlines():
.
.
.
Ber has it right.
To clarify, the default iteration behavior of a file object is to return the next line. so "for nextLine in f" will give you the same results as "for nextLine in f.readlines()".
See the file object documentation for details: http://docs.python.org/library/stdtypes.html#bltin-file-objects

If you want to do something via ssh, why not use the Python SSH module?

Try this page, best info on popen I have found so far....
http://jimmyg.org/blog/2009/working-with-python-subprocess.html

How to redirect stderr in Python?

I would like to log all the output of a Python script. I tried:
import sys
log = []
class writer(object):
def write(self, data):
log.append(data)
sys.stdout = writer()
sys.stderr = writer()
Now, if I "print 'something' " it gets logged. But if I make for instance some syntax error, say "print 'something# ", it wont get logged - it will go into the console instead.
How do I capture also the errors from Python interpreter?
I saw a possible solution here:
http://www.velocityreviews.com/forums/showpost.php?p=1868822&postcount=3
but the second example logs into /dev/null - this is not what I want. I would like to log it into a list like my example above or StringIO or such...
Also, preferably I don't want to create a subprocess (and read its stdout and stderr in separate thread).

I have a piece of software I wrote for work that captures stderr to a file like so:
import sys
sys.stderr = open('C:\\err.txt', 'w')
so it's definitely possible.
I believe your problem is that you are creating two instances of writer.
Maybe something more like:
import sys
class writer(object):
log = []
def write(self, data):
self.log.append(data)
logger = writer()
sys.stdout = logger
sys.stderr = logger

You can't do anything in Python code that can capture errors during the compilation of that same code. How could it? If the compiler can't finish compiling the code, it won't run the code, so your redirection hasn't even taken effect yet.
That's where your (undesired) subprocess comes in. You can write Python code that redirects the stdout, then invokes the Python interpreter to compile some other piece of code.

I can't think of an easy way. The python process's standard error is living on a lower level than a python file object (C vs. python).
You could wrap the python script in a second python script and use subprocess.Popen. It's also possible you could pull some magic like this in a single script:
import os
import subprocess
import sys
cat = subprocess.Popen("/bin/cat", stdin=subprocess.PIPE, stdout=subprocess.PIPE)
os.close(sys.stderr.fileno())
os.dup2(cat.stdin.fileno(), sys.stderr.fileno())
And then use select.poll() to check cat.stdout regularly to find output.
Yes, that seems to work.
The problem I foresee is that most of the time, something printed to stderr by python indicates it's about to exit. The more usual way to handle this would be via exceptions.
---------Edit
Somehow I missed the os.pipe() function.
import os, sys
r, w = os.pipe()
os.close(sys.stderr.fileno())
os.dup2(w, sys.stderr.fileno())
Then read from r

To route the output and errors from Windows, you can use the following code outside of your Python file:
python a.py 1> a.out 2>&1
Source: https://support.microsoft.com/en-us/help/110930/redirecting-error-messages-from-command-prompt-stderr-stdout

Since python 3.5 you can use contextlib.redirect_stderr
with open('help.txt', 'w') as f:
with redirect_stdout(f):
help(pow)

For such a request, usually it would be much easier to do it in the OS instead of in Python.
For example, if you're going to run "a.py" and record all the messages it will generate into file "a.out", it would just be
python a.py 2>&1 > a.out
The first part 2>&1 redirects stderr to stdout (0: stdin, 1:stdout, 2:stderr), and the second redirects that to a file called a.out.
And as far as I know, this command works in Windows, Linux or MacOS! For other file redirection techniques, just search the os plus "file redirection"

I found this approach to redirecting stderr particularly helpful. Essentially, it is necessary to understand if your output is stdout or stderr. The difference? Stdout is any output posted by a shell command (think an 'ls' list) while sterr is any error output.
It may be that you want to take a shell commands output and redirect it to a log file only if it is normal output. Using ls as an example here, with an all files flag:
# Imports
import sys
import subprocess
# Open file
log = open("output.txt", "w+")
# Declare command
cmd = 'ls -a'
# Run shell command piping to stdout
result = subprocess.run(cmd, stdout=subprocess.PIPE, shell=True)
# Assuming utf-8 encoding
txt = result.stdout.decode('utf-8')
# Write and close file
log.write(txt)
log.close()
If you wanted to make this an error log, you could do the same with stderr. It's exactly the same code as stdout with stderr in its place. This pipes an error messages that get sent to the console to the log. Doing so actually keeps it from flooding your terminal window as well!
Saw this was a post from a while ago, but figured this could save someone some time :)

import sys
import tkinter
# ********************************************
def mklistenconsswitch(*printf: callable) -> callable:
def wrapper(*fcs: callable) -> callable:
def newf(data):
[prf(data) for prf in fcs]
return newf
stdoutw, stderrw = sys.stdout.write, sys.stderr.write
funcs = [(wrapper(sys.stdout.write, *printf), wrapper(sys.stderr.write, *printf)), (stdoutw, stderrw)]
def switch():
sys.stdout.write, sys.stderr.write = dummy = funcs[0]
funcs[0] = funcs[1]
funcs[1] = dummy
return switch
# ********************************************
def datasupplier():
i = 5.5
while i > 0:
yield i
i -= .5
def testloop():
print(supplier.__next__())
svvitch()
root.after(500, testloop)
root = tkinter.Tk()
cons = tkinter.Text(root)
cons.pack(fill='both', expand=True)
supplier = datasupplier()
svvitch = mklistenconsswitch(lambda text: cons.insert('end', text))
testloop()
root.mainloop()

Python will not execute your code if there is an error. But you can import your script in another script an catch exceptions. Example:
Script.py
print 'something#
FinalScript.py
from importlib.machinery import SourceFileLoader
try:
SourceFileLoader("main", "<SCRIPT PATH>").load_module()
except Exception as e:
# Handle the exception here

To add to Ned's answer, it is difficult to capture the errors on the fly during the compilation.
You can write several print statements in your script and you can stdout to a file, it will stop writing to the file when the error occurs. To debug the code you could check the last logged output and check your script after that point.
Something like this:
# Add to the beginning of the script execution(eg: if __name__ == "__main__":).
from datetime import datetime
dt = datetime.now()
script_dir = os.path.dirname(os.path.abspath(__file__)) # gets the path of the script
stdout_file = script_dir+r'\logs\log'+('').join(str(dt.date()).split("-"))+r'.log'
sys.stdout = open(stdout_file, 'w')
This will create a log file and stream the print statements to the file.
Note: Watch out for escape characters in your filepath while concatenating with script_dir in the second line from the last in the code. You might want something similar to raw string. You can check this thread for this.