I am struggling a bit to get a package to work, so I would like to just get the simplest possible test case to work.
Here is my current attempt.
Inside of a folder called Python_experiment I have two files: a jupyter notebook with the code
from .pleasejustwork import eat_muffin
and a file called pleasejustwork.py with the code
def eat_muffin():
print('i ate a muffin')
When I run the line from the jupyter notebook I get the error "attempted relative import with no known parent package". What am I missing?
The syntax you’re using is for a python package. To achieve this, place a file, __init__.py in the directory. It can be empty. If you’d like to use that package from anywhere, write a setup.py script to build and install your package. There are a lot of good tutorials on how do that, like in the python docs. Then you could do
from python_experiment.pleasejustwork import eatmuffin or from another file in the package from .pleasejustwork import eatmuffin
If you’re just trying to learn about modules, you can simply take out that leading period
from pleasejustwork import eatmuffin
Related
I'm building a pyd file via pybind11. There's no python-only code in the project (not even in the final wheel). I'm packing this prebuilt pyd into a wheel package. It's all working well so far, but I've got one small issue. Every time I want to use the functions from the pyd file (which is actually the primary "source" of code) I have to type the following: from python_lib_name.pyd_name import pyd_exported_class example: from crusher.crusher import Shard. This looks pretty lame, is there any way to prevent this and let the developer simply use the from crusher import Shard syntax?
Also, I'm not sure what information to provide, obviously, I wouldn't like to throw the whole project at you unnecessarily. I'm glad to provide any details by editing.
how about this: put your pyd in a folder and include a __init__.py that import the stuff from the pyd
my_project
|---my_pyd_lib
| |---my_pyd_lib.pyd
| |---__init__.py
|---#the other stuff
and in that init just put
#__init__.py
from .my_pyd_lib import *
the dot in the import make it a relative import useful to make sure that import the thing in the same folder as that file, it also make sure you import your thing if it happens to share a name with some other package/module you happens to have installed
One way to make a pyd file simply importable is to use the Python interpreter's -m flag. For example, if your file is called foo.pyd and is located in the current directory, you can import it by running the following command:
python -m foo
This will cause the Python interpreter to load the module from foo.pyd and then execute its contents as if they were written in a normal .py file. You can also use this technique to import modules that are located in different directories; just specify the path to the module as an argument to -m.
Another way to make a pyd file simply importable is to convert it into a normal .py file.
I am creating a tool I plan to put on Github. It is very general however I want to also include some examples of its usage. As such I have set up the following folder structure.
This tool is for python 3.
repository/
commonTool.py
commonTool2.py
specificUsage/
runTheSpecificUsage.py
helpRunTheSpecificUsage.py
Now both of the scripts in the specificUsage/ folder will import the methods in commonTool.py and commonTool2.py.
My issue is ideally the user would be able to go
python repository/specificUsage/runTheSpecificUsage.py
However I cant get this to work. It never is able to import the functions that are in the folder above it. I have tried a variety of various posts on how to import a file from a super folder with no luck.
How should I be setting up these folders? Should I have one init.py or two? Where?
You can create a setup.py at the top level along with commonTool.py and commonTool2.py. Inside your setup.py, put the following line:
import setuptools
setuptools.setup(packages=setuptools.find_packages())
Then put an __init__.py in the same level, as well as in specificUsage/. You should be able to import from specificUsage like this:
import commonTool
After setting up your files, from the top level run:
pip install -e .
You may also want to consider that Python has strong naming conventions for modules and packages and frowns upon camelcase in general. You can read more here if you like.
I used below solution for importing dependencies.
I found this solution works if I run the code in Pycharm but not in Terminal.
The error message in Terminal is "cannot find graphics.primitive".
I'm using Mac and Python 3.5.
Why I see different behaviors from the Terminal and Pycharm?
How may I make the solution work for both?
http://chimera.labs.oreilly.com/books/1230000000393/ch10.html#_solution_169
Making a Hierarchical Package of Modules
Problem
You want to organize your code into a package consisting of a hierarchical collection of modules.
Solution
Making a package structure is simple. Just organize your code as you wish on the file-system and make sure that every directory defines an init.py file. For example:
graphics/
__init__.py
primitive/
__init__.py
line.py
fill.py
text.py
formats/
__init__.py
png.py
jpg.py
Once you have done this, you should be able to perform various import statements, such as the following:
import graphics.primitive.line
from graphics.primitive import line
import graphics.formats.jpg as jpg
You need to make sure that the graphics package is in the Python search path. PyCharm does this by extending sys.path as follows:
import sys
sys.path.extend(['/Users/hackworth/Development/graphics_parent_dir', '/Applications/PyCharm.app/Contents/helpers/pycharm', '/Applications/PyCharm.app/Contents/helpers/pydev'])
You can do the same in your code replacing /Users/hackworth/graphics_parent_dir with the appropriate path, or you can include the full path to graphics_parent_dir in the PYTHONPATH environment variable. See the Python documentation for details.
Another option would be to place the graphics package into a location the is searched by default on your system.
I'm self-taught in the Python world, so some of the structural conventions are still a little hazy to me. However, I've been getting very close to what I want to accomplish, but just ran into a larger problem.
Basically, I have a directory structure like this, which will sit outside of the normal python installation (this is to be distributed to people who should not have to know what a python installation is, but will have the one that comes standard with ArcGIS):
top_directory/
ArcToolbox.tbx
scripts/
ArcGIStool.py (script for the tool in the .tbx)
pythonmod/
__init__.py
general.py
xlrd/ (copied from my own python installation)
xlwt/ (copied from my own python installation)
xlutils/ (copied from my own python installation)
So, I like this directory structure, because all of the ArcGIStool.py scripts call functions within the pythonmod package (like those within general.py), and all of the general.py functions can call xlrd and xlwt functions with simple "import xlrd" statements. This means that if the user desired, he/she could just move the pythonmod folder to the python site-packages folder, and everything would run fine, even if xlrd/xlwt/xlutils are already installed.
THE PROBLEM:
Everything is great, until I try to use xlutils in general.py. Specifically, I need to "from xlutils.copy import copy". However, this sets off a cascade of import errors. One is that xlutils/copy.py uses "from xlutils.filter import process,XLRDReader,XLWTWriter". I solved this by modifying xlutils/copy.py like this:
try:
from xlutils.filter import process,XLRDReader,XLWTWriter
except ImportError:
from filter import process,XLRDReader,XLWTWriter
I thought this would work fine for other situations, but there are modules in the xlutils package that need to import xlrd. I tried following this advice, but when I use
try:
import xlrd
except ImportError:
import os, sys, imp
path = os.path.dirname(os.path.dirname(sys.argv[0]))
xlrd = imp.load_source("pythonmod.xlrd",os.path.join(path,"xlrd","__init__.py"))
I get a new import error: In xlrd/init.py, the info module is called (from xlrd/info.py), BUT when I use the above code, I get an error saying that the name "info" is not defined.
This leads me to believe that I don't really know what is going on, because I thought that when the init.py file was imported it would run just like normal and look within its containing folder for info.py. This does not seem to be the case, unfortunately.
Thanks for your interest, and any help would be greatly appreciated.
p.s. I don't want to have to modify the path variables, as I have no idea who will be using this toolset, and permissions are likely to be an issue, etc.
I realized I was using imp.load_source incorrectly. The correct syntax for what I wanted to do should have been:
imp.load_source("xlrd",os.path.join(path,"xlrd","__init__.py"))
In the end though, I ended up rewriting my code to not need xlutils at all, because I continued to have import errors that were causing many more problems than were worth dealing with.
Let's say I have vtk module in my Python site packages, and from application with own Python distribution I want to access this module.
I tried couple of things like:
import sys
sys.path.append("C:\Python27\Lib\site-packages")
sys.path.append("C:\Python27\Lib\site-packages\vtk")
import vtk
lut = vtk.vtkLookupTable()
but it fails to load module properly:
AttributeError: 'module' object has no attribute 'vtkLookupTable'
If I do same from default Python interpreter all is fine.
Now I thought to make a wrapper of vtk in this application site packages, with simple __init__.py resolving paths, so that when I do import vtk it will hopefully load right thing, but I have no experience with Python packages to try to make this work
To put it simple, how can I wrap module from arbitrary folder, in Python site packages by making folder with same name as referenced package and simple __init__.py file?
Remove these lines:
sys.path.append("C:\Python27\Lib\site-packages")
sys.path.append("C:\Python27\Lib\site-packages\vtk")
The site-packages will already be on your python path. Adding a package/folder within that python path (especially at the first level), will just mess with your imports. How is this vtk package structured?
/path/to/site-packages/
vtk/
__init__.py
vtk.py
In this case, to access a function within vtk:
from vtk import vtk
lut = vtk.vtkLookupTable()
It all comes down to how the folder is arranged. You could also do this:
import vtk
lut = vtk.vtk.vtkLookupTable()
Do not try to hack python importing by creating proxy modules simply because you're not understanding how python importing is working. The error was quite clear. The attribute vtkLookupTable did not exist on whatever it was you imported. You imported the wrong thing. Fix it.
You should very very very very rarely have to manipulate the sys.path manually. When you do have to, you should know that it's the right reason - not to work around something you're not fully understanding.
I had trouble with python paths when I first started with python. It can be frustrating, but coming to understand how it works is necessary. What can help you is something like the following:
import vtk
print dir(vtk)
That will print the attributes of vtk, so you can explore exactly what is in the package or module in cases like this where you think you're importing the right thing.
After re-reading your question, it seems like this is a different python install you're talking about. The answer is to install this package into the other python install, or include this package as a top level import by copying the folder into the root level of your application.
"C:\Python27\Lib\site-packages" is already on your python path. So appending path is unnecessary. Remove:
import sys
sys.path.append("C:\Python27\Lib\site-packages")
sys.path.append("C:\Python27\Lib\site-packages\vtk")
Create a new folder called 'vtk\' in "C:\Python27\Lib\site-packages", then create a new python file named __init__.py in "C:\Python27\Lib\site-packages\vtk" and put your own module vtk.py in this directory.
Using:
import vtk
or
from vtk import vtk
to use your own module.