When I use the tilde character in the subprocess call I'm getting an error. Otherwise the program runs fine.
Program
#!/usr/local/bin/python
import subprocess
subprocess.call(["ls","-lrth","~"])
Error
ls: cannot access ~: No such file or directory
Tilde (~) is the shell shortcut for the user home directory. If you want to list all the files/directories in the user home directory you can expand the path using
os.path.expanduser.
#!/usr/bin/env python
import subprocess
import os
subprocess.call(["ls","-lrth",os.path.expanduser("~")])
Related
I'm following along with Google's Python class, and the person in the videos always runs his scripts from the interactive session in command line using "./". Whenever I try it, I just get a syntax error. How can I use ./ to run scripts? I'm using Windows 10
To run a script from the command line you need to use the syntax
python3 script.py
Now on Unix systems, it's possible to add a shebang to the first line of the script as followings
#!/usr/bin/env python3
This then allows the shell syntax './name.py' to work. But windows doesn't have this mechanism. Instead, you need to create an 'association' between the .py extension and the python executable ('right click', 'open with'). Or just use the full syntax. Both require the python executable to be in your path, and generally on windows both python 2 and 3 will have the same executable name
I'm running a wget in Python via os.system.
Is there anyways to hide the output? I tried
> /dev/null
and tried running the command with a $ in front of it.
Use the subprocess module instead.
Using subprocess.call (which is a helper function for some more advanced subprocess features), you can redirect stdout and stderr to file objects. If you open /dev/null (the os module has os.devnull which is a platform-independant path of the null device that can help), you can hand it to subprocess.call and suppress all output
import os
import subprocess
devnull = open(os.devnull, 'w')
subprocess.call([...], stdout=devnull, stderr=devnull)
I am running an executable from cmd:
*.exe input.inp
I want to run it using python and tried following:
os.system('"*.exe"')
But don't know how to specify input file as well. Any suggestions?
import os
from subprocess import Popen, PIPE
p = Popen('fortranExecutable', stdin=PIPE) #NOTE: no shell=True here
p.communicate(os.linesep.join(["input 1", "input 2"]))
For more please refer to:
Using Python to run executable and fill in user input
I had to launch cmd window and specify input file location from within Python script. This page was really helpful in getting it done.
I used Popen(['cmd', '/K', 'command']) from above page and replaced '/K' with '/C' in it to run and close the cmd window.
import os
os.system(r'pathToExe.exe inputFileOrWhateverOtherCommand')
I am learning basic GUI in Python, and I came across a sample example to read file name from file explorer on Stack Overflow.
from Tkinter import Tk
from tkFileDialog import askopenfilename
Tk().withdraw() # we don't want a full GUI, so keep the root window from appearing
filename = askopenfilename() # show an "Open" dialog box and return the path to the selected file
print(filename)
This particular script is working fine when I am trying to run it in IDLE, but the same is not running if I am trying from command prompt in windows 7.
Python Version: 2.7. Here is the output error which I get.
>>> from Tkinter import Tk
>>> from tkFileDialog import askopenfilename
>>> Tk().withdraw()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "C:\Python27\Lib\lib-tk\Tkinter.py", line 1685, in __init__
self.tk = _tkinter.create(screenName, baseName, className, interactive, wantobjects, useTk, sync, use)
_tkinter.TclError: Can't find a usable init.tcl in the following directories:
C:/Python27/lib/tcl8.5 D:/PyProj/lib/tcl8.5 D:/lib/tcl8.5 D:/PyProj/library D:/library D:/tcl8.5.2/library D:/tcl8.5.2/library
This probably means that Tcl wasn't installed properly
Any pointer to what I am missing here can be of great help.
You just need to copy two folders from tcl folder to the Lib folder
tcl8.5 and tk8.5
In case you are using Virtualenv on Windows I found a solution here: https://github.com/pypa/virtualenv/issues/93
I copied the "tcl" folder from C:\Python27\ over to the root of the new Virtualenv, Tkinter.Tk() shows a new window without throwing an exception.
I am running Python 2.7 on Windows 7.
Hit a similar problem after installing Activestate Python and TCL. I found the following page solved the problem for me: ActiveState Python install problem. The fix was to copy the contents of C:\Python27\tcl into C:\Python27\Lib.
Another potential solution (given by user i-shenl in a different ActiveState thread on the same issue) is to set the environment variable $TCL_LIBRARY to point to the tcl library folder ("C:/Python27/tcl", in the question). If you set this system-wide or account-wide (via System Properties), it will affect other programs that use a TCL Library (if any are installed). If you're using Powershell, you can set this variable in your profile to limit its affects to programs run from the shell.
I hit the same problem on Ubuntu 17.04 with virtualenvwrapper for 64 bit Python 2.7
I add tk and tcl library paths in local postactivate script
Go to your virtualenv: workon your-env-name
Edit local postactiave script with your favourite editor, for ex:
gedit $VIRTUAL_ENV/bin/postactivate
Locate tk and tcl library paths. In postactivate script, export TK_LIBRARY and TCL_LIBRARY with appropriate paths. Add this lines to your script with modified paths:
TK_LIBRARY=/home/kamil/anaconda2/pkgs/tk-8.5
TKPATH=/home/kamil/anaconda2/pkgs/tk-8.5
TCL_LIBRARY=/home/kamil/anaconda2/lib/tcl8.5
export TCL_LIBRARY TK_LIBRARY TKPATH
Restart your virtualenv: deactivate and workon your-env-name again.
If you are hitting this kind of error in a python -m venv NAME kind of virtual environment (and you actually have tcl installed in your system), then you need to export the paths similarly as suggested by Kamil Czerski in a previous post for virtualenv.
To find out what are your TK and TCL paths, run a python script outside of the venv (source):
import tkinter
root = tkinter.Tk()
print(root.tk.exprstring('$tcl_library'))
print(root.tk.exprstring('$tk_library'))
Open your venv configuration file bin/activate and find the place where they export PATH and insert after this (insert correct paths from step 1):
TCL_LIBRARY="/tcl/path/from/step/1"
TK_LIBRARY="/tk/path/from/step/1"
TKPATH="/tk/path/from/step/1"
export TCL_LIBRARY TK_LIBRARY TKPATH
Deactivate (if it was activated) and source again your venv:
deactivate
source bin/activate
The "Tcl missing"-error should be gone.
IDLE is probably setting the path required for TCL. To find out what path is being used by IDLE, compare the output of sys.path from IDLE and without IDLE. Then you can add the location of init.tcl either using an environment variable or programatically. See Xenomorph suggestion.
All you need to do is copy tcl 8.6 and tcl 8.5 from tcl file to Lib file on in python.
Python-tcl-tcl8.5 to Python-Lib
Go to directory in which all of your python dependencies are stored
Example:
Python37
-DLLs
-Doc
-etc
-include
-Lib
-libs
-Scripts
-tcl
-python.exe
Go to tcl folder, copy the tcl8.5 and tk8.5 folder
Paste these folders in the Lib folder
This solution works for Windows 10 users
I am new to python, just got the learning python book and got stuck with the spam.py in the command line. The book says to make a file named spam.py and then ask python to run this by typing
%python spam.py
I have added the python to my PATH as it was C:\Python27 so I can call Python in the Windows CMD, but this just will not run. The error I receive is
>>>python spam.py
File "<stdin>", line 1
python spam.py
^
SyntaxError: invalid syntax
I appreciate any help that you can give.
Your problem is that you're trying to run your code from within the Python interpreter itself (the >>> prompt is the giveaway here since that's the Python prompt).
Exit from the interpreter (with CTRL-Z and ENTER for Windows) and run it from cmd.exe (the c:\> is the prompt in the example below):
c:\> python spam.py
From within the interpreter, you can also run an external file with:
execfile('spam.py')
Could you post the code from spam.py...
You seem to be trying to run the spam.py from the Python interpreter. Go to where the file is in Windows Explorer and launch it from there, using the C:\Python2.7\python.exe CLI.
By the way, since you didn't understand the syntax error warning, please see:
http://dictionary.reference.com/browse/SYNTAX
http://dictionary.reference.com/browse/SEMANTICS
You are trying to execute Python script file within the interpreter. Come out from the Python interpreter by pressing CTRL+Z and then ENTER key.
Then execute with the command :
Say, C:/> python spam.py
In order to run a python program you have to run program in Command Line not in Python Interpreter (press Windows Sign + R and type cmd.exe)
Moreover you have to remember to be exactly in the directory where your file is saved, e.g.:
If the file file is C:\Python27\spam.py you have to be in C:\Python27.
To change the directory:
use dir to display the folders and files in current place
use cd to change your directory (e.g. C:\Python27\>cd Spam moves you to C:\Python27\Spam
use Tab key to autocomplete names of the commands, folders and files
As you said you have added Python to PATH and followed my instructions, the statement below should work perfectly
python spam.py
Hope I could help.
If for example, your file is in G: drive, type this in cmd:
python G:/myfile.py
Basically, type in the path. Just doing "cd" won't work in Python