In my particular setting, I have a set of python modules that include auxiliary functions used in many different other modules. I putted them into a LIBS folder and I have other folder at the same path level those are including other modules that are doing certain jobs by using the help of these LIBS modules. Presently, I do this for all the modules to import LIBS modules.
import sys
sys.path.insert(0, '../LIBS')
import lib_module1
import lib_module2
....
As the project getting larger, this starts to be pain in the neck. I need to write down a large set of import statements for these auxiliary LIBS modules for each new module.
Is there any way to automatically import all these LIBS modules for the other modules that are in the folders living at the same path lelvel with LIBS folder?
For this, you can use
__init__.py
Kindly refer Modules and Stackoverflow.
Indeed there is! Start treating your LIBS modules as "real" modules (or packages) that are installed into the system like any other.
This means you will have to write a setup.py script to install your code. Generally this is done inside your development directory, then your module is installed with:
$ sudo python setup.py install
This will install your module under the site-packages subdirectory of wherever Python libraries are stored on your system.
I suggest starting by copying someone else's working setup.py and supporting files, then modifying to suit your packages. For example, here is my quoter module.
Fair warning: This is a pretty big step. Not only will you learn to deploy your module locally, you can also publish it on PyPI if you wish. The step of moving to true packages will encourage you to write more and more standard documentation, to develop and run more tests, to adopt more rigorous version specifications, to more clearly identify and define code dependencies, and take many other "professionalization" steps. These all pay dividends in better, more reliable, more portable, more easily deployed code--but I'd be lying if I didn't admit the learning curve can be steep at times.
Related
I want to know if I can create a python script with a folder in the same directory with all the assets of a python module, so when someone wants to use it, they would not have to pip install module, because it would import from the directory.
Yes, you can, but it doesn't mean that you should.
First, ask yourself who is suposed to use that code.
If you plan to give it to consumers, it would be a good idea to use a tool like py2exe and create executable file which would include all modules and not allow for code to be changed.
If you plan to share it with another developer, you might want to look into virtual environments and requirements.txt file.
There are multiple reasons why sharing modules is bad idea:
It is harder to update modules later, at least without upgrading whole project.
It uses more space on version control, which can create issues on huge projects with hundreds of modules and branches
It might be illegal as some licenses specifically forbid including their code in your source code.
The pip install of some module might do different things depending on operating system version or installed packages. The modules on your machine might be suboptimal on someone else's machine, and in some instances might not even work.
And probably more that I can't think of right now.
The only situation where I saw this being unavoidable was when the module didn't support python implementation the application was running on. The module was changed, and its source was put under lib folder with the rest of the libraries.
I think you can add the directory with python modules into PYTHONPATH. Then people want to use those modules just need has this envvar set.
https://docs.python.org/3/using/cmdline.html#envvar-PYTHONPATH
I'm using Python to develop few company-specific applications. There is a custom shared module ("library") that describes some data and algorithms and there are dozens of Python scripts that work with this library. There's quite a lot of these files, so they are organized in subfolders
myproject
apps
main_apps
app1.py
app2.py
...
utils
util1.py
util2.py
...
library
__init__.py
submodule1
__init__.py
file1.py
...
submodule2
...
Users want to run these scripts by simply going, say, to myproject\utils and launching "py util2.py some_params". Many of these users are developers, so quite often they want to edit a library and immediately re-run scripts with updated code. There are also some 3rd party libraries used by this project and I want to make sure that everyone is using the same versions of these libs.
Now, there are two key problems I encountered:
how to reference (library) from (apps)?
how to manage 3rd party dependencies?
The first problem is well-familiar to many Python developers and was asked on SO for many times: it's quite difficult to instruct Python to import package from "....\library". I tested several different approaches, but it seems that python is reluctant to search for packages anywhere, but in standard libraries locations or the folder of the script itself.
Relative import doesn't work since script is not a part of a library (and even if it was, this still doesn't work when script is executed directly unless it's placed in the "root" project folder which I'd like to avoid)
Placing .pth file (as one might think from reading this document) to script folder apparently doesn't have any effect
Of course direct meddling with sys.path work, but boilerplate code like this one in each and every one of the script files looks quite terrible
import sys, os.path
here = os.path.dirname(os.path.realpath(__file__))
module_root = os.path.abspath(os.path.join(here, '../..'))
sys.path.append(python_root)
import my_library
I realize that this happens because Python wants my library to be properly "installed" and that's indeed would be the only right way to go had this library was developed separately from the scripts that use it. But unfortunately it's not the case and I think that re-doing "installation" of library each time it's changed is going to be quite inconvenient and prone to errors.
The second problem is straightforward. Someone adds a new 3rd party module to our app/lib and everyone else start seeing import problems once they update their apps. Several branches of development, different moments when user does pip install, few rollbacks - and everyone eventually ends using different versions of 3rd party modules. In my case things are additionally complicated by the fact that many devs work a lot with older Python 2.x code while I'd like to move on to Python 3.x
While looking for a possible solution for my problems, I found a truly excellent virtual environments feature in Python. Things looked quite bright:
Create a venv for myproject
Distribute a Requirements.txt file as part of app and provide a script that populates venv accordingly
Symlink my own library to venv site_packages folder so it'll be always detected by Python
This solution looked quite natural & robust. I'm explicitly setting my own environment for my project and place whatever I need into this venv, including my own lib that I can still edit on the fly. And it indeed work. But calling activate.bat to make this python environment active and another batch file to deactivate it is a mess, especially on Windows platform. Boilerplate code that is editing sys.path looks terrible, but at least it doesn't interfere with UX like this potential fix do.
So there's a question that I want to ask.
Is there a way to bind particular python venv to particular folders so python launcher will automatically use this venv for scripts from these folders?
Is there a better alternative way to handle this situation that I'm missing?
Environment for my project is Python 3.6 running on Windows 10.
I think that I finally found a reasonable answer. It's enough to just add shebang line pointing to python interpreter in venv, e.g.
#!../../venv/Scripts/python
The full project structure will look like this
myproject
apps
main_apps
app1.py (with shebang)
app2.py (with shebang)
...
utils
util1.py (with shebang)
util2.py (with shebang)
...
library
__init__.py
submodule1
__init__.py
file1.py
...
submodule2
...
venv
(python interpreter, 3rd party modules)
(symlink to library)
requirements.txt
init_environment.bat
and things work like this:
venv is a virtual python environment with everything that project needs
init_environment.bat is a script that populates venv according to requirements.txt and places a symlink to my library into venv site-modules
all scripts start with shebang line pointing (with relative path) to venv interpreter
There's a full custom environment with all the libs including my own and scripts that use it will all have very natural imports. Python launcher will also automatically pick Python 3.6 as interpreter & load the relevant modules whenever any user-facing script in my project is launched from console or windows explorer.
Cons:
Relative shebang won't work if a script is called from other folder
User will still have to manually run init_environment.bat to update virtual environment according to requirements.txt
init_environment scrip on Windows require elevated privileges to make a symlink (but hopefully that strange MS decision will be fixed with upcoming Win10 update in April'17)
However I can live with these limitations. Hope that this will help others looking for similar problems.
Would be still nice to still hear other options (as answers) and critics (as comments) too.
I am creating a Python package with multiple modules. I want to make sure that when I import modules within the package that they are importing only from the package and not something outside the package that has the same name.
Is the correct way of doing this is to use relative imports? Will this interfere when I move my package to a different location on my machine (or gets installed wherever on a customer's machine)?
Modern relative imports (here's a reference) are package-relative and package-specific, so as long as the internal structure of your package does not change you can move the package as a whole around wherever you want.
While Joran Beasley's answer should work as well (though does not seem necessary in those older versions of Python where absolute imports aren't the default, as the old style of importing checked within the package's directory first), I personally don't really like modifying the import path like that when you don't have to, especially if you need to load some of those other packages or modules that your modules or packages now shadow.
A warning, however: these do require that the module in question is loaded as part of a package, or at least have their __name__ set to indicate a location in a package. Relative imports won't work for a module when __name__ == '__main__', so if you're writing a simple/casual script that utilizes another module in the same directory as it (and want to make sure the script will refer to the proper directory, things won't work right if the current working directory is not set to the script's), you could do something like import os, sys; sys.path.insert(0, os.path.dirname(os.path.abspath(__file__))) (with thanks to https://stackoverflow.com/a/1432949/138772 for the idea). As noted in S.Lott's answer to the same question, this probably isn't something you'd want to do professionally or as part of a team project, but for something personal where you're just doing some menial task automation or the like it should be fine.
the sys.path tells python where to look for imports
add
import sys
sys.path.insert(0,".")
to the top of your main python script this will ensure local packages are imported BEFORE builtin packages (although tbh I think this happens automagically)
if you really want to import only packages in your folder do
import sys
sys.path = ["."]
however I do not recommend this at all as it will probably break lots of your stuff ...
most IDE's (eclipse/pycharm/etc) provide mechanisms to set up the environment a project uses including its paths
really the best option is not to name packages the same as builtin packages or 3rd party modules that are installed on your system
also the best option is to distribute it via a correctly bundled package, this should more than suffice
We have a lot small projects that share common utility "projects"
Example:
utility project math contains function add
project A and project B both need math.add
project A has nothing to do with project B
so is it a good idea to have 3 git repositories (project_A,project_B and math) and clone them locally as
/SOMWHERE/workspace/project_A
/SOMWHERE/workspace/math
and have in /SOMWHERE/workspace/project_A/__init__.py something like
import sys
sys.path.append('../math')
import math
math.add()
I have read Structuring Your Project but that doesn't handle SCM and sharing modules.
So to sum up my question: is
sys.path.append('../math')
import math
good practice or is there a more "pythonic" way of doing that?
Submodules are a suboptimal way of sharing modules like you said in your comments. A better way would be to use the tools offered by your language of choice, i.e Python.
First, create virtualenvs to isolate every project python environment. Use pip to install packages and store dependencies in a requirements.txt file.
Then, you can create a specific package for each of your utils library using distutils and share it on Pypi.
If you don't want to release your packages into the wild, you can also host your own Pypi server.
Using this setup, you will be able to use different versions of your libraries and work on them without breaking compatibility with older code bases. You will also avoid using submodules, that are difficult to use with git.
all of what you describe (3 projects) sounds fine except that you shouldn't mess around with sys.path. instead, set the PYTHONPATH environment variable.
also, if you were not aware of distutils i am guessing you may be new to python development, and may not know about virtualenv. you should use that too (it allows you to develope against a "clean" python version that has no packages, or only the packages you install for that env).
I need to ship a collection of Python programs that use multiple packages stored in a local Library directory: the goal is to avoid having users install packages before using my programs (the packages are shipped in the Library directory). What is the best way of importing the packages contained in Library?
I tried three methods, but none of them appears perfect: is there a simpler and robust method? or is one of these methods the best one can do?
In the first method, the Library folder is simply added to the library path:
import sys
import os
sys.path.insert(0, os.path.join(os.path.dirname(__file__), 'Library'))
import package_from_Library
The Library folder is put at the beginning so that the packages shipped with my programs have priority over the same modules installed by the user (this way I am sure that they have the correct version to work with my programs). This method also works when the Library folder is not in the current directory, which is good. However, this approach has drawbacks. Each and every one of my programs adds a copy of the same path to sys.path, which is a waste. In addition, all programs must contain the same three path-modifying lines, which goes against the Don't Repeat Yourself principle.
An improvement over the above problems consists in trying to add the Library path only once, by doing it in an imported module:
# In module add_Library_path:
sys.path.insert(0, os.path.join(os.path.dirname(__file__), 'Library'))
and then to use, in each of my programs:
import add_Library_path
import package_from_Library
This way, thanks to the caching mechanism of CPython, the module add_Library_path is only run once, and the Library path is added only once to sys.path. However, a drawback of this approach is that import add_Library_path has an invisible side effect, and that the order of the imports matters: this makes the code less legible, and more fragile. Also, this forces my distribution of programs to inlude an add_Library_path.py program that users will not use.
Python modules from Library can also be imported by making it a package (empty __init__.py file stored inside), which allows one to do:
from Library import module_from_Library
However, this breaks for packages in Library, as they might do something like from xlutils.filter import …, which breaks because xlutils is not found in sys.path. So, this method works, but only when including modules in Library, not packages.
All these methods have some drawback.
Is there a better way of shipping programs with a collection of packages (that they use) stored in a local Library directory? or is one of the methods above (method 1?) the best one can do?
PS: In my case, all the packages from Library are pure Python packages, but a more general solution that works for any operating system is best.
PPS: The goal is that the user be able to use my programs without having to install anything (beyond copying the directory I ship them regularly), like in the examples above.
PPPS: More precisely, the goal is to have the flexibility of easily updating both my collection of programs and their associated third-party packages from Library by having my users do a simple copy of a directory containing my programs and the Library folder of "hidden" third-party packages. (I do frequent updates, so I prefer not forcing the users to update their Python distribution too.)
Messing around with sys.path() leads to pain... The modern package template and Distribute contain a vast array of information and were in part set up to solve your problem.
What I would do is to set up setup.py to install all your packages to a specific site-packages location or if you could do it to the system's site-packages. In the former case, the local site-packages would then be added to the PYTHONPATH of the system/user. In the latter case, nothing needs to changes
You could use the batch file to set the python path as well. Or change the python executable to point to a shell script that contains a modified PYTHONPATH and then executes the python interpreter. The latter of course, means that you have to have access to the user's machine, which you do not. However, if your users only run scripts and do not import your own libraries, you could use your own wrapper for scripts:
#!/path/to/my/python
And the /path/to/my/python script would be something like:
#!/bin/sh
PYTHONPATH=/whatever/lib/path:$PYTHONPATH /usr/bin/python $*
I think you should have a look at path import hooks which allow to modify the behaviour of python when searching for modules.
For example you could try to do something like kde's scriptengine does for python plugins[1].
It adds a special token to sys.path(like "<plasmaXXXXXX>" with XXXXXX being a random number just to avoid name collisions) and then when python try to import modules and can't find them in the other paths, it will call your importer which can deal with it.
A simpler alternative is to have a main script used as launcher which simply adds the path to sys.path and execute the target file(so that you can safely avoid putting the sys.path.append(...) line on every file).
Yet an other alternative, that works on python2.6+, would be to install the library under the per-user site-packages directory.
[1] You can find the source code under /usr/share/kde4/apps/plasma_scriptengine_python in a linux installation with kde.