When I run vim in a subprocess, I have the script that created that subprocess continue printing miscellaneous status updates. However the updates get printed on top of my vim instance. How do I create a behavior where I only see the output when I quit vim (:q).
I'm running the subprocess like this:
def callVim():
# Open the file with the text editor
EDITOR = os.environ.get('EDITOR','vim')
call([EDITOR, temp_loc])
try:
print('Starting vim process...')
vim = Process(target = callVim)
vim.start()
except KeyboardInterrupt:
print("Terminating vim server.")
vim.terminate()
vim.join()
And this is what the overlaid output looks like ('Check if target updated...' being the output):
Thank you for any and all help.
Any kind of suggestion is welcome.
I'm running tmux if that matters?
EDIT:
So i tried rerouting the sys.stdout to a variable before calling on vim, like so:
so = sys.stdout = StringIO()
EDITOR = os.environ.get('EDITOR','vim')
call([EDITOR, self.temp_loc])
But it still printed over vim.
EDIT2:
Also I need to keep the output somewhere because i use it elsewhere in the program.
Related
I'm not sure but I imagine that there may be issues similar to mine, but I have not found any that has been satisfactory.
When I open my Jupyter Lab and execute a cell as below (code01), it remains with the status of * (see figure01 below) meaning that it is still running the code, but the output of the out1.txt file is printed correctly.
I would like to know if it is normal for the cell to remain running in this circumstances described from code01.
code01:
import sys
file = open('out1.txt', 'a')
sys.stdout = file
print("house")
file.close()
figure01:
Because you redirect the stdout to a file and then close it you are breaking the IPython kernel underneath: there is no way for any stdout to be correctly processed by the kernel afterwards (cannot write to a closed file). You can reproduce it by executing your code in the IPython console rather than in a notebook. To fix this you could rebind the original stdout back:
import sys
file = open('out1.txt', 'a')
stdout = sys.stdout
sys.stdout = file
print("house")
# before close, not after!
sys.stdout = stdout
file.close()
But this is still not 100% safe; you should ideally use context managers instead:
from contextlib import redirect_stdout
with open('out1.txt', 'a') as f:
with redirect_stdout(f):
print('house')
But for this particular case why not to make use the file argument of the print() function?
with open('out1.txt', 'a') as f:
print('house', file=f)
I have a very simple (test) code which I'm running either from a Linux shell, or in interactive mode, and I have two different behaviours I cannot figure out the reason of.
I have a file generated by a Popen call, previously, where each line is a file path. This is the code used to generate the file:
with open('find.txt','w') as f:
find = subprocess.Popen(["find",".","-name","myfile.out"],stdout=f)
(Incidentally, I was trying to build a PIPE originally, namely inputting the output of this command to a grep command, and since I wasn't successful in any way, I decided to break the problem down and just read the file paths from a file, and process them one by one. So maybe there is a common issue that is blocking me somewhere in this procedure).
Since in this second step I wasn't even able to open and process the files by opening the addresses contained in each line of the find.txt file, I just tried to print the file lines out, because for sure they're available in there:
with open('find.txt','r') as g:
for l in g.readlines():
print(l)
Now, the interesting part:
if I paste the lines above into a python shell, everything works fine and I get my outputs as expected
if, on the other hand, I try to run python test.py, where test.py is the name of the file containing the lines above, no output appears in the shell's stdout.
I've tried sys.stdout.flush() to no avail. I've also inserted some dummy print() statements along the way: everything gets printed but what's after the g.readlines() statement.
Here's the full script I'm trying to make work (a pre-precursor of what I'm actually after, tbh).
#!/usr/bin/env python3
import subprocess
import sys
with open('find.txt','w') as f:
find = subprocess.Popen(["find",".","-name","myfile.out"],stdout=f)
print('hello')
with open('find.txt','r') as g:
print('hello?')
for l in g.readlines():
print('help me!')
print(l)
sys.stdout.flush()
output being:
{ancis:>106> python test.py
hello
hello?
{ancis:>106>
EDIT
I've quickly tried the very same lines (but without the call to find, which isn't available) on my python installation in Windows: it works as expected)
Based on that, I've tried to run the simpler code below:
print('hello')
with open('find.txt','r') as g:
print('hello?')
for l in g.readlines():
print('help me!')
print(l)
sys.stdout.flush()
as a script, in Linux - This also works w/o problems.
This should mean that somehow I'm messing things up with the call to Popen... But what?
This is a race condition.
Your call to
find = subprocess.Popen(["find",".","-name","myfile.out"],stdout=f)
is opening another process and running your find command which takes a bit of time to fully execute.
Python then continues on and reaches the reading of the file portion before the command is fully executed and the file is generated.
Want to test it out?
Add a time.sleep(1) just before the opening of the file.
Full test script:
#!/usr/bin/env python3
import subprocess
import time
with open('find.txt','w') as f:
find = subprocess.Popen(["find",".","-name","myfile.out"],stdout=f)
time.sleep(1)
with open('find.txt','r') as g:
for l in g:
print(l)
To block until the process is complete you can use find.communicate().
With this you can also optionally set a timeout if that's something that you want.
#!/usr/bin/env python3
import subprocess
with open('find.txt','w') as f:
find = subprocess.Popen(["find",".","-name","myfile.out"],stdout=f)
find.communicate()
with open('find.txt','r') as g:
for l in g:
print(l)
Source:
https://docs.python.org/3/library/subprocess.html#subprocess.Popen.communicate
I'm new to Linux, and have been trying to solve an assignment but to no avail.
I have a shell script which prints out lines of a text file in a certain manner (a line within every few seconds):
python << END
import time,random
a= open ('/home/ch/pshety/course/fielding_history.txt','r')
flag =False
for i in range(1000):
b=a.readline()
if i==402 or flag:
print(a.readline())
flag=True
time.sleep(2)
END
sh th.sh
If I run it without trying to redirect it anywhere, I get the output on the terminal. However, when I tried to redirect it into a new text file, it doesn't do anything - the text remains empty:
sh th.sh > debug.txt
I've tried looking for answers, I've stumbled upon a lot of suggestions including tee but nothing helps - the file remains empty.
What am I doing wrong?
Try this:
import time,random
a = open('/home/ch/pshety/course/fielding_history.txt', 'r')
for i in range(1000):
b = a.readline()
if i >= 402:
print(b, flush=True)
time.sleep(2)
Your Python script likely needs to flush the contents of the output buffer before you can see it.
Note: aside from the sleep() call, Unix provides other ways of accomplishing this. I would take a look at man tail and read about the -f and -n switches.
Edit: didn't realize that tail has a switch (-s) to sleep as well!
I am reading about subprocess and playing around with some code.
I'm using Windows 7 with Python3.6
import subprocess
process = subprocess.Popen(['notepad', 'C:\\Users\Amit\Downloads\InsiderTrades.txt'],stdout=subprocess.PIPE, stderr=subprocess.PIPE)
#I'm opening a text file which has a list of stock tickers
stdout1, stderr1 = process.communicate()
print(stdout1.decode('ASCII'))
The output I'm getting is nothing or
b'' as the value for stdout1.
I"m not quite sure what communicate is outputting in this case.
I was under the impression that it would output the text from my text file or it would output anything I type into the text file.
I tried typing into the newly opened text file as well, but I'm still getting the same output , b''
So what am I getting an empty string, despite typing something into the newly opened textfile.
Subprocess is basically as if you run that command in the terminal.
So what you are doing is running
notepad some_file.txt
which just opens a file in notepad, but it doesn't send anything to standard output.
If you run a command that writes something to standard output, then you will have a non-empty stdout1. Try ls for example if you are on a *nix system or dir if on Windows.
I would like to easily test my python programs without constantly using the python shell since each time the program is modified you have to quit, re-enter the python shell and import the program again. I am using a 2012 Macbook pro with OSX. I have the following code:
import sys
def read_strings(filename):
with open(filename) as file:
return file.read().split('>')[1:0]
file1 = sys.argv[1]
filename = read_strings(file1)
Essentially I would like to read into and split a txt file containing:
id1>id2>id3>id4
I am entering this into my command line:
pal-nat184-102-127:python_stuff ceb$ python3 program.py string.txt
However when I try the sys.argv approach on the command line my program returns nothing. Is this a good approach to testing code, could anyone point me in the correct direction?
This is what I would like to happen:
pal-nat184-102-127:python_stuff ceb$ python3 program.py string.txt
['id1', 'id2', 'id3', 'id4']
Let's take this a piece at a time:
However when I try the sys.argv approach on the command line my
program returns nothing
The final result of your program is that it writes a string into the variable filename. It's a little strange to have a program "return" a value. Generally, you want a program to print it's something out or save something to a file. I'm guessing it would ease your debugging if you modified your program by adding,
print (filename)
at the end: you'd be able to see the result of your program.
could anyone point me in the correct direction?
One other debugging note: It can be useful to write your .py files so that they can be run both independently at the command line or in a python shell. How you've currently structured your code, this will work semi-poorly. (Starting a shell and then importing your file will cause an error because sys.argv[1] isn't defined.)
A solution to this is to change your the bottom section of your code as follows:
if __name__ == '__main__':
file1 = sys.argv[1]
filename = read_strings(file1)
The if guard at the top says, "If running as a standalone script, then run what's below me. If you imported me from some place else, then do not execute what's below me."
Feel free to follow up below if I misinterpreted your question.
You never do anything with the result of read_strings. Try:
print(read_strings(file1))