I have both 2.7 and 3.0 versions of the Python interpreter installed (on my Ubuntu 32 system), but one particular script uses 3.0.
Using
#!/usr/bin/python3 -B
will not work when the program is run with python myprogram.py.
And I also need a solution that works also in Windows where I also have both python versions installed.
How can I make the script to run only with the right python version?
Please use virtualenv, which makes isolated Python environments easy.
python = Python to use. # This has to be the absolute path to Python executable
os.execl(python, python, * sys.argv)
This way you can restart the script with the python you want to use. Not really stylish.
I don't know why you can't just launch the program with python3 foo.py, but it's possible to have a python2 program relaunch itself as python3 with something like this.
import sys
if sys.version_info.major != 3:
import os
# replace this process with a python3 process
os.execlp("python3", "python3", *sys.argv)
It's a bad solution though, because now your python3 program can't use anything that's not valid python2 syntax
Please take a look at The wrong python interpreter is called
You have to choose a correct interpreter based on where you installed the desired version of Python and your system variables.
Related
Using Pycharm on Linux mint.
I installed the "future" package for the python interpreter which I'm using. Heres the script.
from tkinter import *
top = Tk()
top.mainloop()
Didn't work. It returns "ModuleNotFoundError: No module named 'tkinter'". Tkinter is infact installed. "python3 -m tkinter" confirms it. And when I compile the same code in the terminal, it displays.
As Bryan says, you're probably not using the Python version you think you're using. PyCharm tends to install its own version of Python. Once you have more than one version of Python installed, things get trickier.
To see what's happening, try running this script:
import sys
print(sys.executable, sys.version)
Or run those similar commands from the command line. That should help clarify matters.
The sys.executable will show you the full path to your Python executable. Great for seeing where the used Python installation is located.
I don't use Python on Linux, but perhaps one of your Python installations is version 2, in which case you would need to use:
from Tkinter import *
which is another way to confirm that the Python is version 2 rather than 3. If this is the case, you'll want to move to Python 3. I don't think anyone writes new projects in Python 2 anymore. It's defunct, purely legacy.
It's also possible that Python is installed on Linux without Tkinter. There are other posts on how to install Tkinter on Linux. For instance, you can check out ImportError: No module named 'Tkinter'
Thanks guys for the help I really appreciate it. But I found out the problem was because of Linux Mint's Software Manager. I initially downloaded pycharm using said software manager but it didnt work which is why I created the post. Then I deleted it, and downloaded pycharm through the tar.gz file from the jetbrains website. After doing that, it seems to work.
As some pundits say that the Python standard library is listed in the Python core documentation for your version, it is built-in by default, you don't have to install it separately from Python itself. For example, math is a standard module, you needn't install it with pip install math.
Non-standard modules are not built-in, you have to install them before you use them in a Python program. For example, lxml is a non-standard module. If not installed, a "no module named lxml" error pops up when you import lxml in the Python shell.
It is time to turn to the topic now, how can I list all non-standard modules used by a Python program?
test.py is a Python program, it is executed with python test.py. How many non-standard modules are called when python test.py is run?
pip freeze shows all installed modules, but some of them are not called by python test.py.
I was wondering the same thing, because I wanted to set up a conda environment for my project by a method other than trial-and-error. What I found worked was to make a bare environment with just python and pylint in it, using, e.g.,
conda create -n myenv python=3 pylint
and then from within that environment run:
pylint /path/to/module --disable=all --enable=import-error
This will nicely list, by file, all of the non-standard imports.
im fairly new to programming in Python and i've been using the terminal to run my code with no problem. Usually by typing python {filename} to run it.
However, recently i got this error:
ImportError: Python is not installed as a framework. The Mac OS X backend will not be able to function correctly if Python is not installed as a framework. See the Python documentation for more information on installing Python as a framework on Mac OS X. Please either reinstall Python as a framework, or try one of the other backends. If you are using (Ana)Conda please install python.app and replace the use of 'python' with 'pythonw'. See 'Working with Matplotlib on OSX' in the Matplotlib FAQ for more information.
then i changed the python {filename} to pythonw {filename} and the code worked. Could someone give me some insight into this error and why it worked by just adding w?
pythonw - run python script allowing GUI. According to the man page for pythonw.
Having several exe's of Python, I would like to specify the command (py or python) to launch a certain version from the command line.
At the moment, I have different versions of Python (2.7, 3.6, 3.7 Anaconda) installed on my Windows machines (7 at work, 10 at home). Unfortunately, the commands in the cmd-prompt are not the same.
The output of the following cmd commands is as follows:
py -> 3.7.1 of Anaconda (work) and 3.7.0 (home)
python -> 2.7.13 (work) and 3.6.2 (home)
pyton2 -> not recognized (work) and 2.7.15 (home)
How can I order the variables, so the same commands call the same version of python? Researching about the path variable I could not find how to define the command that launches a specific python.exe.
I really appreciate your help or a pointing in the right direction.
Kind regards,
Seb
Good Morning,
my apologies, yesterday I did not find this thread here:
In CMD "python" starts Python 3.3, "py" starts Python 2.7, how do I change this?
From now on I will go with "py -X.Y" to start the version of Python I want.
Kind regards,
Seb
I'm still learning python. I have windows 8 and had downloaded 2.7 as well as 3.5 because two modules I used in the past respectively used different python versions. Now though, I'm trying to run a script where the first line is import http.client or http. Neither of these work though. In cmd, python returns 3.5.1 currently and import http.client and import http return with no errors but in my IDE these don't work. Why not?
You can follow the Pycharm documentation here to change the Python version for your project from Python 2 to Python 3.
(In particular, Selecting Python interpreter for a project section)