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The imported modules get unimported after running a python file [duplicate]

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How to prevent python IDLE from restarting when running new script
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Closed 3 years ago.
I noticed that all the modules I import are removed (I can't use them anymore without importing them again) after I run a python file in the python IDE.
Here is the view of my IDE:
Python 3.7.3 (v3.7.3:ef4ec6ed12, Mar 25 2019, 22:22:05) [MSC v.1916 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license()" for more information.
>>> import os
>>> os
<module 'os' from 'C:\\Users\\MN\\AppData\\Local\\Programs\\Python\\Python37\\lib\\os.py'>
>>>
RESTART: C:/Users/MN/AppData/Local/Programs/Python/Python37/python file just ran.py
A python file just ran
>>> os
Traceback (most recent call last):
File "<pyshell#2>", line 1, in <module>
os
NameError: name 'os' is not defined
>>>
For deep view, this was in my file:
print("A python file just ran")
Why is this happening and how to make the imported modules stay in there without importing them again?

I'm not sure if you can make them stay, sorry.
Python restarts when you launch a file in IDLE (it even states RESTART).
Edit: Try defining variables, methods or classes - they too will be gone, not just your imports.
Edit two: You can import your file (python will automaticly execute it), that will not restart python so you will keep what you defined/imported.

Maybe just to add why this is the case...
Every Python program must have some module that is in "control" of the program. This is the same as in C where you have a "main".
If you want to use functions from file_just_ran.py, then you should define those as functions and then import them into your session. Then the session is in control.
If you want the scrip to be in control, then you must do these import etc either in the script, or in a file that that script can import.
Otherwise, how does the interpreter know what to do? You're trying to execute commands in a running python program?
If you just want to run scripts and code in an interpreter in parallel, then open two sessions.

Matlab Engine Python - OSx Anaconda Segfault or DYLD_LIBRARY_PATH error with iPython

After installing the matlab python package in terminal using:
cd "matlabroot\extern\engines\python"
python setup.py install
And trying to run it, I get a segfault:
:~$ python
Python 2.7.10 |Anaconda 2.3.0 (x86_64)| (default, May 28 2015, 17:04:42)
[GCC 4.2.1 (Apple Inc. build 5577)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
Anaconda is brought to you by Continuum Analytics.
Please check out: http://continuum.io/thanks and https://binstar.org
>>> import matlab.engine
Segmentation fault: 11
However, I can get around this by setting DYLD_LIBRARY_PATH after which matlab.engine works:
:~$ export DYLD_LIBRARY_PATH=/System/Library/Frameworks/Python.framework/Versions/Current/lib:$DYLD_LIBRARY_PATH
:~$ python
Python 2.7.6 (default, Sep 9 2014, 15:04:36)
[GCC 4.2.1 Compatible Apple LLVM 6.0 (clang-600.0.39)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import matlab.engine
>>> eng = matlab.engine.start_matlab()
>>> exit()
However, when I try to launch iPython afterwards I get this error:
Traceback (most recent call last):
File "//anaconda/bin/ipython", line 4, in <module>
from IPython import start_ipython
File "//anaconda/lib/python2.7/site-packages/IPython/__init__.py", line 45, in <module>
from .config.loader import Config
File "//anaconda/lib/python2.7/site-packages/IPython/config/__init__.py", line 6, in <module>
from .application import *
File "//anaconda/lib/python2.7/site-packages/IPython/config/application.py", line 19, in <module>
from IPython.config.configurable import SingletonConfigurable
File "//anaconda/lib/python2.7/site-packages/IPython/config/configurable.py", line 12, in <module>
from .loader import Config, LazyConfigValue
File "//anaconda/lib/python2.7/site-packages/IPython/config/loader.py", line 16, in <module>
from IPython.utils.path import filefind, get_ipython_dir
File "//anaconda/lib/python2.7/site-packages/IPython/utils/path.py", line 14, in <module>
import tempfile
File "//anaconda/lib/python2.7/tempfile.py", line 32, in <module>
import io as _io
File "//anaconda/lib/python2.7/io.py", line 51, in <module>
import _io
ImportError: dlopen(//anaconda/lib/python2.7/lib-dynload/_io.so, 2): Symbol not found: __PyErr_ReplaceException
Referenced from: //anaconda/lib/python2.7/lib-dynload/_io.so
Expected in: dynamic lookup
As you can see the python versions are different. I think this is a conflict between my system Python and Anaconda but I'm not sure how to fix it, any help much appreciated.
Thanks.

You need to install libraries using the conda command line install utility, not python. conda help search and conda help install should get you going.

This is not a direct solution, but I was stuck with the same problem and used this workaround. And I should say that I did finally make matlab.engine run in my Python environment, but that it just plain sucked. It couldn't run scripts with embedded scripts in other folders, and I also experienced that it couldn't find some build-in functions. The following is implemented for a Unix machine, but it would not take a lot of modification to make it work in Windows, I believe.
Here's what I did:
Wrote a main Matlab script that could do everything I needed from Matlab.
Ran that script through a subprocess in Python.
In my case I needed do a series of matrix operations for matrix X and return matrix S. The matrix operations required the use of a particular Matlab function. My first idea was to open a Matlab-session with matlab.engine and then manage the matrix operations in Python only calling the Matlab function when needed. Instead (as the bullets state) I wrote a Matlab function ComputeSimilarityMat that takes X, does all necessary operations, and returns S. Then I basically just ran that Matlab function from Python using a subprocess.
This is what the Python script, that manages the Matlab script through a subprocess, looks like:
import subprocess
import numpy as np
def run_matlab(X):
"""Produce trait-similarity matrix S from a trait-space matrix X
Parameters
----------
X : numpy.ndarray
Returns
-------
S : numpy.ndarray
"""
# Dump input in .csv, so Matlab can load it
np.savetxt('X.csv', X, delimiter=",")
# Code executed in Matlab. Important to end with quit;
matlab_code = "X=csvread('X.csv');" \
"S=ComputeSimilarityMat(X);" \
"csvwrite('S.csv',S);" \
"quit;"
# -nosplash suppresses the splash window on startup
matlab_call = ["matlab", "-nodesktop", "-nosplash", "-r", matlab_code]
subprocess.call(matlab_call)
# Load the .csv file that Matlab dumps after finishing
S = np.genfromtxt('X.csv', delimiter=",")
return S
I have to say, I'm sure there's a nicer way to pass an object to Matlab then to have to save and load like this, but it worked for me. Still hoping for an improvement of matlab.engine though, but until then I'm going with this approach.
Note: To run Matlab from command-line/subprocess you need to add the Matlab bin folder to your PATH variable like this:
export PATH="/Applications/MATLAB_R2015a.app/bin:$PATH"
I just put this in my .profile file.

In my case adding things to LD_LIBRARY_PATH (Ubuntu's version of DYLD_LIBRARY_PATH) only made things worse. Instead I had to make sure it did not refer to the Python installation, and had to add a symbolic link from /usr/lib instead. See https://stackoverflow.com/a/45161288/2524427

Can't import the cx_Oracle module unless I'm using an interactive shell

When using Python on an interactive shell I'm able to import the cx_Oracle file with no problem. Ex:
me#server~/ $ python
Python 2.7.6 (default, Mar 22 2014, 22:59:56)
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import cx_Oracle
>>>
As you can see, importing works without a hitch. However, when I try to run a Python script doing the same thing, I get an error:
me#server~/ $ sudo script.py
Traceback (most recent call last):
File "/usr/local/bin/script.py", line 19, in <module>
import cx_Oracle
ImportError: No module named "cx_Oracle'
Here is the important section from script.py:
# 16 other lines above here
# Imports
import sys
import cx_Oracle
import psycopg2
...
I'm befuddled here. Other pertinent information is the server I'm running is Ubuntu 14.04.1 LTS (upgraded from 12.04) 64bit. which python and sudo which python both point to the same location. Also, doing this as root via sudo su - gets the same results; import OK from interactive but error from script.
Nothing other than the OS upgrade happened between when this worked and when it stopped working.

Sorry, all. This was a silly on my part. Turns out the script in question was using Python3, and when the server upgraded, Python3 went from being 3.2 version to being 3.4 version.
Once the cx_Oracle module was set up in the 3.4 version, everything worked as expected.
Phil, your final note talking about the shebang was what lead me to discover this, so kudos to you! The reason I didn't mark your response as the answer was because technically it wasn't but led me on the right path.
Cheers!

sudo starts a new bash environment which is then pointing to a different python executable (different installed modules).
You can verify this with which python and sudo which python
EDIT: so if they point to the same executable, then you should look at sys.path to find differences. In both environemnts you can:
python -c "import sys; print('\n'.join(sys.path))"
sudo python -c "import sys; print('\n'.join(sys.path))"
Look for differences. If there are none:
A common error in import situations like this is that python will first look at the local dir. So if you happen to be running python and importing something what is found locally (i.e. cx_Oracle is a subdir of your current location), you will get an import error if you change directories.
Final note: I have assumed here that the shbang of the script.py points to the same executable as which python. That is, that python script.py and script.py return the same error.

Python error "import: unable to open X server"

I am getting the following errors when trying to run a piece of python code:
import: unable to open X server `' # error/import.c/ImportImageCommand/366.
from: can't read /var/mail/datetime
./mixcloud.py: line 3: syntax error near unexpected token `('
./mixcloud.py: line 3: `now = datetime.now()'
The code:
import requests
from datetime import datetime,date,timedelta
now = datetime.now()
I really lack to see a problem. Is this something that my server is just having a problem with and not the code itself?

those are errors from your command shell. you are running code through the shell, not python.
try from a python interpreter ;)
$ python
Python 2.7.5+ (default, Sep 19 2013, 13:48:49)
[GCC 4.8.1] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import requests
>>> from datetime import datetime,date,timedelta
>>>
>>> now = datetime.now()
>>>
if you are using a script, you may invoke directly with python:
$ python mixcloud.py
otherwise, ensure it starts with the proper shebang line:
#!/usr/bin/env python
... and then you can invoke it by name alone (assuming it is marked as executable):
$ ./mixcloud.py

Check whether your #! line is in the first line of your python file. I got this error because I put this line into the second line of the file.

you can add the following line in the top of your python script
#!/usr/bin/env python3

I got this error when I tried to run my python script on docker with docker run.
Make sure in this case that you set the entry point is set correctly:
--entrypoint /usr/bin/python

Why can't Python find and run my scripts when calling Python from Python command line?

I am in the python command line (using python 2.7), and trying to run a Python script. My operating system is Windows 7. I have set my directory to the folder containing all of my scripts, using:
os.chdir("location").
os.getcwd() returns this location.
When I type:
python myscript.py
I get this error:
File "<stdin>", line 1
python myscript.py
^
SyntaxError: invalid syntax.
What have I done wrong?
The first uncommented line of the script I'm trying to run:
from game import GameStateData

It sounds like you're trying to run your script from within Python. That's not how it works. If you want to run myscript.py, you need to do it from a system command prompt, not from inside the Python interpreter. (For instance, by choosing "Command Prompt" from your start menu. I think it's usually under "Accessories" or something like that.) From there you'll need to change to the directory where your scripts are by using the CD command.

Based on the additional information you have provided it does look like you are issuing the command inside of Python.
EDIT: Maybe part of the confusion comes from the term command line. You are at the command line in both the "Windows command" shell, and also when you are inside the "Python shell".
This is what I get in the command line when inside the Python shell:
D:\Users\blabla \Desktop>python
Python 2.7.2 (default, Jun 12 2011, 15:08:59) [MSC v.1500 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> python testit.py
File "<stdin>", line 1
python testit.py
^
SyntaxError: invalid syntax
>>>
Or this:
>>> os.chdir("..")
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'os' is not defined
>>>
My suggestion would be to open a Windows command shell window with the cmd command and then issue your python myscript.py from there.
For more help it would be helpful to see your code, at least the first few lines where the error occurs and some certainty as to where the python command is being issued.

As the other answers indicate, you are probably in the Python shell unintentionally. But if you really do want to run your script from there, try execfile("myscript.py")

on windows shell run echo %PATH%, and check if your .py is under any of the paths.