Develop Reference

subprocess.call() gives "The system cannot find the path specified." while the file exists and can run that truly

why running
import subprocess
# I'm going to run another python script in anaconda script like this:
#subprocess.call("C:\\ProgramData\\Anaconda3\\Scripts\\activate.bat && python C:\test.py")
# but for simplifying the sample for here I've deleted the second part
# (in the case you didn't install python in the default path, you can replace v_activate_address with the correct address on your computer to see the result)
v_activate_address = "C:\\ProgramData\\Anaconda3\\Scripts\\activate.bat"
subprocess.call(v_activate_address)
gives. (it's not an error):
The system cannot find the path specified.
This code can run my test.py in anaconda environment truly but that line appears which is not desirable.
How should I get rid of that?
[the address is correct please don't say that]
answer to #Dunes comment:

How to change the default python version/path in Rstudio

I am aware that similar questions have been asked before, but I either don't understand the answers, or there aren't any; so I decided to describe my problem in as much detail as possible.
Problem:
RStudio reticulate package uses Python from this path:
"/usr/bin/python"
but I want it to use python from this path - always, as a default:
"/Library/Frameworks/Python.framework/Versions/3.7/bin/python3"
How do I know it happens?
I open RStudio, and create a new python script. A new file with an extension .py is generated. I type something in:
import pandas as pd
and execute (by clicking cmd+enter). I then see what happens in the console - the reticulate package is called:
reticulate::repl_python()
Python 2.7.10 (/usr/bin/python)
Reticulate 1.12 REPL -- A Python interpreter in R.
I would like to permanently change where the reticulate package looks for Python.
From the Terminal I know:
$ python --version
Python 3.7.3
which python3
/Library/Frameworks/Python.framework/Versions/3.7/bin/python3
So, I would like to tell RStudio to always look in this path to find Python 3.7. I have tried to use the following command, run from an R script:
use_python("/Library/Frameworks/Python.framework/Versions/3.7/bin/python3")
but it doesn't do anything - my naive understanding is that this command is useful within an R markdown file, i.e. when I have code that combines R and Python, in separate chunks. I would like to change the path that is used when a Python script is run from within RStudio. Is there some kind of a config file I could edit?
I hope this makes sense. I am not a regular Python user, only started learning now, and I am also not very good with paths, so I would appreciate step-by-step answers.

OK, so I have posted too early - after some more googling I can solve this problem myself, but I think it is worth posting an answer here for people like me (i.e. not path-proficient or python-proficient).
There is something like a config file for R, called .Renviron. In order to access it, use Terminal to go to your home directory (i.e. the one that you go to when you type 'cd'). If you have never used this file before, it might not exist, in which case you need to create it.
Once in your home directory, type:
ls -a
then check on the list of files that appears whether .Renviron is there. Below are instructions what if you already have .Renviron (IF YES), and what if you don't (IF NO).
IF NO, type:
touch .Renviron
which creates the file.
IF YES, just proceed as below (without using the touch command).
Write:
nano .Renviron
the .Renviron file will open. In it, add a line that says:
RETICULATE_PYTHON="enter your desired path here"
so, in my case, this is:
RETICULATE_PYTHON="/Library/Frameworks/Python.framework/Versions/3.7/bin/python3"
now save the file by exiting nano (ctrl+x) and clicking 'y' when it asks whether to save changes (press 'y' then press enter).
restart you RStudio. It should work now. I hope this is useful!

GAE Python : dev_appserver.py: error: too few arguments

I am trying to run the basic helloworld code described here https://cloud.google.com/appengine/docs/python/. However, whenever I try the dev_appserver.py helloworld/ command, I get a usage error for the dev_appserver.py command.
I have installed Python 2.7 and also have Python 2.7 Anaconda installed on my system. Could the Anaconda Python be the cause of the issue?
The file structure of my code is as follows:
Project
helloworld
app.yaml
helloworld.py
README.md
I have tried executing the dev_appserver.py helloworld/ command from inside the 'Project' folder and the 'helloworld' folder. But I get the same error in both cases.
Any help would be greatly appreciated!
Thanks!

I think I have found the "real" problem behind this error.
Tried putting some print statements in the dev_appserver.py file and found that what ever argument we are giving is not being passed and hence the error. On googling came across this SO post which explains the problem. On doing that change the following command worked flawlessly :D
dev_appserver.py app.yaml
Quoting that SO answer for easier reference:
I think I solved this. For some reason there is a SECOND place in the registry (besides that shown by the file associations stored in HKEY_CLASSES_ROOT\Python.File\shell\open\command):
[HKEY_CLASSES_ROOT\Applications\python.exe\shell\open\command]
#="\"C:\\Python25\\python.exe\" \"%1\" %*"
This seems to be the controlling setting on my system. The registry setting above adds the "%*" to pass all arguments to python.exe (it was missing in my registry for some reason).

You just need to execute the dev_appserver.py with path to app.yaml in the command itself, as suggested in comments.

I think OP could've identified a potential issue when describing multiple Python installations.
If I don't specify which Python installation (I thought I only had one...), then, it fails:
C:\Python27>"C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\bin\dev_appserver.py" "C:\users\jessmine\documents\ttbtamer\app.yaml"
usage: dev_appserver.py [-h] [-A APP_ID] [--host HOST] [--port PORT]
...etc...
dev_appserver.py: error: too few arguments
But if I specify which Python to use by invoking Python first, # C:\Python27\python.exe, then it works:
C:\Python27>"C:\Python27\python.exe" "C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\bin\dev_appserver.py" "C:\users\jessmine\documents\ttbtamer\app.yaml"
INFO 2016-11-18 10:09:14,299 devappserver2.py:769] Skipping SDK update check.
Anyway since I don't think I have other Python installations on my computer, then I may be misinterpreting the difference here. But for me, the fix is to explicitly invoke python.exe.
(And to be clear, I know about putting the Python.exe location into %PATH%, but I expected that if it wasn't there, that the error would've been something like "'dev_appserver.py' is not recognized as an internal or external command", rather than executing and printing a Python error....)
EDIT
After changing the "associate a file type or protocol with a specific program" (example here) for *.py to explicitly use C:\Python27\python.exe , then I no longer needed to manually invoke C:\Python27\python.exe in my cmd; i.e. my first example worked correctly :
C:\Program Files (x86)\Google\Cloud SDK\google-cloud-sdk\bin>dev_appserver.py "C:\users\jessmine\documents\ttbtamer\app.yaml"
INFO 2016-11-18 10:33:50,269 devappserver2.py:769] Skipping SDK update check.

I had the same problem. I even installed everything on a fresh machine and I was getting the same error again.
So I "debugged" dev_appserver.py and I discovered that the argument passed to it (i.e. 'app.yaml' or '.' or '\hello_world') was not passed down to the following code file:
...\google-cloud-sdk\platform\google_appengine\google\appengine\tools\devappserver2\devappserver2.py
In this file the arguments were checked, producing the infamous error "too few arguments".
Out of desperation for the time lost, I made a quick (and for sure ugly) patching.
I commented out at lines 302 and 303 the validation rule:
parser.add_argument(
'config_paths', metavar=arg_name, nargs='+', help=arg_help)
At line 758 I replaced:
options.config_paths, options.app_id)
with a static file name:
{'app.yaml'}, options.app_id)
At least now I am able again to start the server and develop my application. Now that I can work again, I will try to understand better how to correct the problem.
I'm not a Python nor a Google App Engine expert, so I hope someone will propose a better correction and a better explanation of the problem, because I cannot believe that Google can release such bugged code!

I suggest cd into your helloworld folder and and run dev_appserver.py . don't forget the ending dot '.' sign.
Hope it works

In my case I was able to resolve this issue by peforming following two actions:
1). added "python" in the start of the command
2). provided full path to the "dev_appserver.py" file.
So in Google docs you will find to execute the following:-
> dev_appserver.py ./ --php_executable_path=/path/to/php-cgi
(note that I was trying to run the php example and on windows environment here...)
Instead running the following command worked:
> python "c:\<path to the directory containing the dev_appserver.py script>\dev_appserver.py" ./ --php_executable_path=/path/to/php-cgi

What tools should I use to profile Python code on window 7

I want to profile python code on Widnows 7. I would like to use something a little more user friendly than the raw dump of cProfile. In that search I found the GUI RunSnakeRun, but I cannot find a way to download RunSnakeRun on Windows. Is it possible to use RunSnakeRun on windows or what other tools could I use?
Edit: I have installed RunSnakeRun now. That's progress, thanks guys. How do you run it without a linux command line?
Edit 2: I am using this tutorial http://sullivanmatas.wordpress.com/2013/02/03/profiling-python-scripts-with-runsnakerun/ but I hang up at the last line with "python: can't open file 'runsnake.py': [Errno 2] No such file or directory "

The standard solution is to use cProfile (which is in the standard library) and then open the profiles in RunSnakeRun:
http://www.vrplumber.com/programming/runsnakerun/
cProfile, however only profiles at the per-functions level. If you want line by line profiling try line profiler:
https://github.com/rkern/line_profiler

I installed runsnake following these installation instructions.
The step python runsnake.py profile.pfl failed because the installation step (easy_install SquareMap RunSnakeRun) did not create a file runsnake.py.
For me (on Ubuntu), the installation step created an executable at /usr/local/bin/runsnake. I figured this out by reading the console output from the installation step. It may be in a different place on Windows, but it should be printed in the output of easy_install. To read a profile file, I can execute /usr/local/bin/runsnake profile.pfl.

There's also py-spy, written in Rust, safe to use even in production, without modifying any code.
Works on Windows, to install run pip install py-spy.
From there you can run py-spy record -o profile.svg -- python myprogram.py which produces nice flame graphs.

fuse-python xmp.py - Not able to create a file

I am writing a Network File System, and I have started by trying to understand the xmp.py provided with python-fuse.
Well basically I'm sending all the calls over the network, executing it on the server-side and sending the result to the client and returning it to the user. These parts are working perfectly fine.
The problem I am facing is that, the xmp.py is not able to create a file and hence the problem is showing up in my Network File System too.
The steps I have followed are:
Installed fuse-python by:
sudo apt-get install python-fuse
Then I go into the directory where xmp.py is located:
cd /usr/share/doc/python-fuse/examples/
I ran the xmp.py program with the following command-line arguments
python xmp.py -o root=/home/user /tmp/fuse
where /home/user will be replicated or mounted on /tmp/fuse
Then I cd into the /tmp/fuse directory and try to make a file with cat, like:
cd /tmp/fuse
cat > temp.txt
I get the error
bash: temp.txt: Invalid argument
After a lot of poking around, I believe that this is due to the function
def getattr(self, path):
return os.lstat("." + path)
When I do a cat > temp.txt, os.lstat("./temp.txt") is called and an error is thrown as the file /home/user/temp.txt is not found. After this the program gets stuck for a while and slows down my computer.
Please help me figure out what I'm doing wrong.
Thanks.

I think i have figured it out, the problem that i saw was once os.lstat("./temp.txt") fails, the file class's __init__ method is called and then immediately truncate is called and the program returns.
One solution that i followed was to not use the file class at all, and to implement the Fuse class' open/create to make the file.
This approach worked for me. If anyone has a better suggestion please let me know. I would like to use the object-oriented approach and use the file class.