I'm just getting into programming; I've made some simple scripts and am hoping to learn how to do things with them. I have a question about where these files "live" on my computer, and if that's important. Let's say I have a script in the directory users/me/desktop/project/skeleton/ called webproject.py. In the skeleton/ directory I also have tests/; does tests/ have to be in skeleton/ or can it be in some random place like my desktop/?
Further, if one of my scripts imports a module that I've created, does it matter where that's located? If I make a script with a function that outputs the nth fibonacci number, and save it on my desktop, can my webproject.py script from users/me/desktop/project/skeleton/ import it?
Any links/resources would be helpful.
It of course matters where you place your files. There sure is more than one directory called "tests", so your Python interpreter cannot guess what "tests" directory it should pick. There is no magic in your computer, I am sorry. ;) But there is something called "Python path". All modules which are saved in a directory specified in the Python path can be imported from anywhere. To use webproject.py from "project/skeleton/" you would have to include "project/skeleton/" in your Python path or make it a package.
There is a nice chapter in the official Python tutorial about modules. :)
Related
I am looking for a solution that will allow me to use py file as a little library.
Short description:
I have a py script and there are a lot of common functions in it.
Instead of each time use a big file I want to throw all common functions into separate py file, put into folder Tools and use it when I need.
My problems is that I cannot import this file from Tools, because my script does not see it.
My folder structure:
C:\some\folders\here\my\folder\script.py
C:\some\folders\here\Tools\Library\library.py
Also, it is not good for me to user init.py, because I haven't any python project, it is just one file without any other things.
Are there any normal solutions?
Python interpreter searches for modules in 3 places:
current directory, that means the directory from which you run the script with your import statement
list of directories from PYTHONPATH
installation-dependent list of directories, this is configures when Python in installed
You can also modify sys.path at runtime and include a directory where your module is located, but this is the worst solution and it's usually discouraged to do so.
Setting PYTHONPATH will most likely be a solution in your situation.
I wrote a small python program and again I am struggling with producing a good structure.
A few days ago I read a blog and many other websites, which advise against from a import b imports and recommend to use always import a.b "project absolute" path (the whole path from the project root to what I want to import) imports. That as a background.
I included a __main__.py so that I can run my program with python -m <directory>, which was another recommendation of someone on stackoverflow in one of the hundreds of python import questions. It is supposed to help keeping code runnable and testable with the same import structure, which was a problem in another project of mine.
Now what I want it, that from anywhere in my system, I can run python -m <dir of my code> and not only from one directory up the RSTCitations directory.
How can I achieve that, without:
python path manipulations (which are a dirty hack)
changing my imports somehow and getting a not recommended import structure
doing other dark magic to my code
I want to stick to best practices in organizing my code but still want it to be runnable from wherever I am in the terminal.
Example of fail
When I run the program as described from another directory completely unrelated to my program, I get for example the following error:
/home/user/development/anaconda3/bin/python: No module named /home/user/development/rst-citations-to-raw-latex/RSTCitations
However the path is correct. That is exactly where the code is.
You can :
install your program with pip ( see Installing Python packages from local file system folder with pip )
put your module in the python import path (and/or edit PYTHONPATH in the environment for the users that need to use it)
If you don't need other users to 'import' your library but just use it as a standalone program, you can also just put a symlink/script to your program, makeing it runnable from a directory which is in your PATH.
Python newbie here. Am using Anaconda (on Windows 7) by recommendation of a friend.
What I want to be able to do is make a change to my class in Notepad++ and then test it in my Python command prompt window immediately.
This is a simple question that I can't seem to find the answer: in what directory does a default installation of Anaconda expect me to be storing my .py files (so that I can easily load them using import <MODULE NAME>)?
My PATH variable is set to:
C:\USERS\<USERNAME>\Anaconda3;C:\USERS\<USERNAME>\Anaconda3\Scripts
(this is the default)
Am I supposed to be working out of the Scripts directory...? There's already a lot of files in there.
What do most people do? Perhaps add another folder to the PATH variable and work out of there? Do you add a new folder to PATH for each project or is there a way that makes more sense? I already have a Projects directory I use for everything else. I'd like to just be able to work out of there.
I am coding in Notepad++. I don't really want to bother setting up/learning an IDE (I'm just doing relatively simple I/O file manipulation that I have previously been doing in Excel... the horror).
Sorry for the extremely newbie question. I searched and could not find anything relevant.
EDIT AFTER ACCEPTED ANSWER:
The problem was that I was running python.exe from the Start menu. I did not realize that you are supposed to open a CMD window in the folder (SHIFT+RIGHT CLICK) you are working in (such as C:\USERS\<USERNAME>\MY PYTHON STUFF) and run python from there.
This might be what you're attempting. Note that I also use Anaconda.
My path:
C:\Users\...\Documents\Python Scripts\
import_sample.py
class class_sample(object):
def __init__(self):
self.x = ["I", "am", "doing", "something", "with", "Python"]
test.py
from import_sample import class_sample
c = class_sample()
y = c.x
print " ".join(y)
Result:
I am doing something with Python
[Finished in 0.1s]
Notice how being in the same folder allows me to import without having to install, per se. Basically, just make sure that the modules you need are in the same folder as your main.py and you're good.
EDIT:
Done from the terminal.
Notice how I cd into the above folder and activated python there. Since I was inside that folder, any modules inside it can be imported without any problems, alongside other system-wide modules installed as well.
I have a Django app and I'm getting an error whenever I try to run my code:
Error: No module named django_openid
Let me step back a bit and tell you how I came about this:
I formatted my computer and completely re-installed everything -- including virtualenv, and all dependent packages (in addition to Django) required for my project based on settings in my requirements.txt folder
I tried doing python manage.py syncdb and got the error
I googled the issue, and many people say it could be a path problem.
I'm confused as to how I go about changing the path variables though, and what exactly they mean. I found some documentation, but being somewhat of a hack-ish noob, it kind of goes over my head.
So my questions are:
What exactly is their purpose -- and are they on a system based level based on the version of Python or are they project dependent?
How can I see what mine are set to currently?
How can I change them (ie. where is this .profile file they talk of and can I just use a text editor)
Any input you would have would be great as this one is stumping me and I just want to get back to writing code :-)
The path is just the locations in your filesystem in which python will search for the modules you are trying to import. For example, when you run import somemodule, Python will perform a search for somemodule in all the locations contained in the path (sys.path variable).
You should check the path attribute in sys module:
import sys
print sys.path
It is just a regular list, sou you could append/remove elements from it:
sys.path.append('/path/to/some/module/folder/')
If you want to change your path for every python session you start, you should create a file to be loaded at startup, doing so:
Create a PYTHONSTARTUP environment variable and setting it to your startup file. E.g.: PYTHONSTARTUP=/home/user/.pythonrc (in a unix shell);
Edit the startup file so it contains the commands you want to be auto-executed when python is loaded;
An example of a .pythonrc could be:
import sys
sys.path.append('/path/to/some/folder/')
Do you really need to alter the path? It's always best to actually think about your reasons first. If you're only going to be running a single application on the server or you just don't care about polluting the system packages directory with potentially unnecessary packages, then put everything in the main system site-packages or dist-packages directory. Otherwise, use virtualenv.
The system-level package directory is always on the path. Virtualenv will add its site-packages directory to the path when activated, and Django will add the project directory to the path when activated. There shouldn't be a need to add anything else to the path, and really it's something you should never really have to worry about in practice.
I am using Python 2.5 on CentOS 5.5
I have got a file called MultipartPostHandler.py, I am supposed to use it like this:
import MultipartPostHandler
But I dont know where should I put the file MultipartPostHandler.py so I can use it. Thanks a lot!
http://docs.python.org/tutorial/modules.html#the-module-search-path
When a module named spam is imported,
the interpreter searches for a file
named spam.py in the current
directory, and then in the list of
directories specified by the
environment variable PYTHONPATH. This
has the same syntax as the shell
variable PATH, that is, a list of
directory names. When PYTHONPATH is
not set, or when the file is not found
there, the search continues in an
installation-dependent default path;
on Unix, this is usually
.:/usr/local/lib/python.
Actually, modules are searched in the
list of directories given by the
variable sys.path which is initialized
from the directory containing the
input script (or the current
directory), PYTHONPATH and the
installation- dependent default. This
allows Python programs that know what
they’re doing to modify or replace the
module search path.
So, you have to put it into the current directory or use sys.path to show your program where the searched module is.
The easiest is to put it in the same folder as the code you're writing.
If you got it from somebody who provides an installer, then to be safe, just run the installer.
If it's just something you grabbed specifically for this project, put it in the same folder as the .py files that you're writing.
Otherwise (if you're planning to use it for a few projects and don't want to copy/paste the file), the safest place to put it is probably in the /lib/site-packages sub-directory of the directory where Python is installed.
The easiest - yes, is to put it in the same directory where you have the importer python code. Also, you can export PYTHONPATH environment variable which points to the directory (or directories separated by :) where you have MultipartPostHandler.py. Another option: make it distributable. This will be useful if you are going to publish your code.