This question already has answers here:
Auto-load a module on python startup
(5 answers)
Closed 9 years ago.
I'm using python on Windows. And I'm trying to find a way to import some default module when starting python. It means, when starting python, some modules should be already imported, just like builtins. Is there any way?
Thanks.
If you mean while going into the interactive mode, just make a small startup script. Instead of just launching python with:
python
try instead:
python -i startupImports.py
startupImports.py:
import time
from collections import defaultdict
from customclass import myclass
#...etc
Define a PYTHONSTARTUP environment variable and point it to a python file and it will be loaded when you start python interactively without a command line script.
I have my PYTHONSTARTUP point to a .pythonrc where I try to import a __boot__.py (bootstrap) in the current directory for any interactive python session.
try:
from __boot__ import *
except Exception:
pass
There's a bunch of other things in my pythonrc like __future__ imports, readline setup, etc.
One option is adding your import to sitecustomize.py. This file is automatically imported at startup. This will be loaded whether Python is started in interactive mode or not. To quote the docs:
[In site.py] an attempt is made to import a module named sitecustomize, which can perform arbitrary site-specific customizations. It is typically created by a system administrator in the site-packages directory. If this import fails with an ImportError exception, it is silently ignored.
Another option is to set the PYTHONSTARTUP environment variable to a startup script with your import. This will only be executed if Python is started in interactive mode, though.
Related
I am studying python, both 3. and 2. I started a few days ago.
I want to know the differences between site module and interpreter.
I got this question from
Python exit commands - why so many and when should each be used?
Those explanations are very clear but it's still hard to me.
If I am understanding your question correctly,site is a module in Python. A module is a file containing Python definitions and statements. In order to use the functions (for ex: exit() or quit(), you need to import the site module as those respective functions are defined in there.
The Python interpreter is the program that reads and executes Python code. This includes source code, pre-compiled code, scripts - in this case you reference, you would need to import the site module into your current Python interpreter session, in order to use say exit() or quit() in that given session.
So, the process of this particular question would be:
* Activate the Python interpreter by typing into your respective terminal the version of Python you have installed on your computer, ex. python3.
* In the Python interpreter, type import site
Hope that helps Hwan.
I assume you are stuck on understanding:
"Nevertheless, quit should not be used in production code. This is
because it only works if the site module is loaded. Instead, this
function should only be used in the interpreter."
Basically, what that is saying is that quit is a part of a module loaded in the python interpreter. That module's name, is site.
Firstly, the python interpreter is what you use to run python scripts or environments. It interprets python commands. For example, if you write a = 1 in a script or python environment, the interpreter takes that command and executes it without compiling it. (If it was a language like c you would need to compile the script before you run it).
Secondly, a module is a pre-written file that can define functions, classes and variables. When you write import numpy into python, you are importing the module, numpy. Therefore when they say "this only works if the site module is loaded", that means that import site must be executed.
When you start a python interpreter (by typing python into your command shell), it automatically imports site, which has sys, venv and main etc. which are all required to run an active interpreter session.
I've been trying to port a Maya based python project over to PyCharm but I'm having trouble running unit tests.
Maya provides its own python interpreter (mayapy.exe) with a zipped version of the python stdlib (in this case, 'Python27.zip') AFAIK there's nothing special about the stdlib here, but to run the native maya functions you have to use MayaPy rather than a generic python.
The problem appears to be that the jetBrains test runner (utRunner.py) wants to get os.system and it's barfing because it uses a specific import routine that doesn't allow for zip files. It tries this:
def import_system_module(name):
if sys.platform == "cli": # hack for the ironpython
return __import__(name)
f, filename, desc = imp.find_module(name)
return imp.load_module('pycharm_' + name, f, filename, desc)
and fails with this error:
ImportError: No module named os
I think because this is bypassing the zip import hook.
There's one solution posted here, which is basically to unzip the standard library zip. I'm reluctant to do that because I might need to run the tests on machines where I don't have admin rights. I'm also reluctant to patch the code above since I'm not clear how it fits in to the whole test process.
So: how to run tests with a zipped standardlib using PyCharm, without unzipping the library or tweaking the PyCharm install too much?
For lurkers: I was unable to find a better solution than the one linked above, so it was necessary to unzip the 2.7 standard libary into a loose folder. Inelegant, but it works,.
There was a further wrinkle that maya users need to watch out for: PyCharm does not like tests which run Maya.standalone -- the standalone session did not exit properly, so when running tests (in onr ore more files) that called
import maya.standalone
maya.standalone.initialize()
The pycharm test runner would hang on completion. After much frustration I found that adding an atexit handler to the test code would allow the standalone to exit in a way that PyCharm could tolerate:
def get_out_of_maya():
try:
import maya.commands as cmds
cmds.file(new=True, force=True)
except:
pass
os._exit(0) # note underscore
import atexit
atexit.register(get_out_of_maya)
This pre-empts the atexit hook in Maya and allows the tests to complete to the satisfaction of the Pycharm runner. FWIW, it also helps if you are running MayaPy.exe from a subprocess and executing your tests that way.
I ended up just editing Pycharm's utrunner.py file. It already imports os at the top of the file, so I'm not sure why it calls import_system_module. The import command automatically handles zip files. Also if you put the maya.standalone in the runner file, you don't need to call it in any of your test files.
#os = import_system_module("os")
#re = import_system_module("re")
import re
try:
import maya.standalone
maya.standalone.initialize()
except ImportError:
pass
I'm using Pycharm 5.0.1.
This question already has answers here:
Passing options to Python executable in non-interactive mode
(4 answers)
Closed 7 years ago.
I would like to execute a script work.py in Python, after executing some initialization script init.py.
If I were looking for an interactive session, executing python -i init.py or setting PYTHONSTARTUP=/path/to/init.py would do the trick, but I am looking to execute another script.
Since this is a generic case which occurs often (init.py sets environment and so is the same all of the time), I would highly prefer not referencing init.py from work.py. How could this be done? Would anything change if I needed this from a script instead of from the prompt?
Thank you very much.
More generally than in the accepted answer of C0deH4cker, this is discussed in the Python manual in Section 2.2.5 - Cusomization Modules. The basic idea is, to get the location of the special start-up script, one needs to execute the following Python code, e.g. from the interactive session of the interpreter:
>>> import site
>>> site.getusersitepackages()
'/home/user/.local/lib/python3.2/site-packages'
The output should be exactly such a location, in the file sitecustomize.py.
Python has a special script that is run on startup. On my platform it is located at /usr/lib/python2.5/site-packages/sitecustomize.py IIRC. So, you could either put init.py in that directory alongside a sitecustomize.py script that imports it, or just paste the content of init.py in the sitecustomize.py.
Let's say I have this python script script.py and I load it in the interpreter by typing
import script
and then I execute my function by typing:
script.testFunction(testArgument)
OK so far so good, but when I change script.py, if I try to import again the script doesn't update. I have to exit from the interpreter, restart the interpreter, and then import the new version of the script for it to work.
What should I do instead?
You can issue a reload script, but that will not update your existing objects and will not go deep inside other modules.
Fortunately this is solved by IPython - a better python shell which supports auto-reloading.
To use autoreloading in IPython, you'll have to type import ipy_autoreload first, or put it permanently in your ~/.ipython/ipy_user_conf.py.
Then run:
%autoreload 1
%aimport script
%autoreload 1 means that every module loaded with %aimport will be reloaded before executing code from the prompt. This will not update any existing objects, however.
See http://ipython.org/ipython-doc/dev/config/extensions/autoreload.html for more fun things you can do.
http://docs.python.org/library/functions.html#reload
reload(module)
Reload a previously imported module. The argument must
be a module object, so it must have been successfully imported before.
This is useful if you have edited the module source file using an
external editor and want to try out the new version without leaving
the Python interpreter. The return value is the module object (the
same as the module argument).
An alternative solution that has helped me greatly is to maintain a copy of sys.modules keys and pop the new modules after the import to force re-imports of deep imports:
>>> oldmods = set(sys.modules.keys())
>>> import script
>>> # Do stuff
>>> for mod in set(sys.modules.keys()).difference(oldmods): sys.modules.pop(mod)
>>> import script
When I start the interactive django shell through manage.py, by executing
python -v manage.py shell
from the project directory, I see a lot of modules of format django.package.module getting imported in the verbose output but still I have to import them to use it in the shell.
The same happens when I just run the Python shell (with the -v argument). For example I see this in the verbose output,
import os # precompiled from /usr/local/gdp/lib/python2.4/os.pyc
but still i have to do import os to import and use the os module. What is being imported that am seeing in the verbose output and why I have to import them explicitly again to use them in the shell? Does Python load some essential modules while starting the shell or is it some kind of behind-the-scene magic?
-v traces the first import of a module -- the one that actually loads the module (executes its code, and so may take a bit of time) and sticks it into sys.modules.
That has nothing to do whether your interactive session (module __main__) gets the module injected into its namespace, of course. To ensure module 'goo' does get into the namespace of module 'X' (for any X, so of course including __main__... among many, many others), module 'X' just needs to import goo itself (a very fast operation indeed, if sys.modules['goo'] is already defined!-).
Python loads the site module implicitly when starting up, which may in turn import other modules for its own use. You can pass -S to disable this behavior.
They are getting imported (look at sys.modules) and references to the module are created in whichever modules have imported it.
When you do an import in your shell, if the module has already been imported, you will just get a copy of the reference to it in sys.modules