Develop Reference

Different module import in Mac python vs. spyder

I have recently asked this question about importing an arbitrary amount of modules in python. I received two good answers. Both worked when I programmed it in spyder.
Today I ran the script from my terminal as test, since I'm planning to move my code to my server. But this time the script crashed with this Traceback:
File "evaluation.py", line 27, in __init__
self.solvers.append( __import__(file_name[:-3]) ) #cut away .py
ImportError: No module named 'v00'
The file architecture looks like this:
-evaluation.py
-evaluation
-v00.py
-v01.py
The code in evaluation.py which causes trouble is this one:
os.chdir('evaluation')
for file_name in glob.glob("*.py"):
self.solvers.append( __import__(file_name[:-3]) ) #cut away .py
for idx, solver in enumerate(self.solvers):
self.dqn.append(solver.DQNSolver() )
Why does this work in spyder but not in the terminal? They both use python 3.5 and I double checked that both are in the folder "evaluation" when executing the malicious line.

The typical way to handle this would be to turn the folder into a package by adding an empty __init__.py file and then import from the package with import evaluation.v00 (or the equivalent __import__ function call). But you may run into problems as your main script has the same name as the package. I would suggest renaming one or the other
-evaluationscript.py
-evaluation
-__init__.py (empty file)
-v00.py
-v01.py
And then you probably need to use import_module instead of __import__ to populate solvers with the actual module (instead of the package).
I'm not familiar with spyder, but if the same code is working there, then it may be adding the evaluation folder to the search path either with the PYTHONPATH env var, or by modifying sys.path.
When you run a script, the path of the script is added to the default search path for module imports, but changing the folder using os.chdir won't affect that search path.

ImportError: cannot import name

I got a library called google-translate-python. https://github.com/terryyin/google-translate-python
Basically, I copied/pasted the translate.py file to my python27/lib directory. I imported it like so:
from translate import Translator
And I put in something like this:
theTranslate = Translator(to_lang="sp")
translation = theTranslate.translate("hello")
And I'm using pycharm btw so I haven't gotten any errors, it is saying the methods are there and everything.
However, I get the error: ImportError: cannot import name Translator
Did I import the library wrong? that's all I can think of. Because the methods are there and running.

I figured it out... the library I was trying to import had the same name as my actual python file. So my python file was called translate.py and my library I was trying to import was called translate. I don't know how to differentiate it.. but changing the name of my python file fixed it. wow.. that took about 3 hours to realize.

Does it show in the list of packages installed under Pycharm interpreter? You need to add the package to this list and then it becomes available to you for import. It is available as one of the packages there.

Based on the github page the package can be installed from the source using:
python setup.py install
Another option is to save the translate.py to the local directory or another directory.
If translate.py is not in the local directory you can add the module path using:
sys.path.append('PATH_TO_TRANSLATE.PY')

If you can't use pip the simplest way to get this installed would be to do download the source code (.zip file) and unzip it.
Open a terminal (where you have access to python) and change to the folder (cd <the path to the folder>) you have unzipped, and then run:
python setup.py install
This will make sure the files end up in the right location (which on Windows is actually in C:\Python27\Lib\site-packages).

Python: wrapper for C++ requires access to .dll files

I made a Python wrapper for an SDK written in C++ using SWIG and built using Microsoft Visual Studio 2010 in Windows 7.
It's been a success, with the module.py and _module.pyd being generated. However, this wrapper heavily depends on a couple .dll files located in the SDK folder outside PythonXY folder.
After I moved the module.py and module.pyd into PythonXY/Lib/site-packages/, and tried running import module, the following error occurs:
ImportError: DLL load failed: The specified module could not be found.
Then, I tried to change the Python working directory to the directory where the .dll files exist, using os.chdir() method from Python module os. This time, running import module output no error. I continued to access the wrapped C++ classes and functions and they worked just fine.
My questions are:
How can I "link" the path containing the .dll files so whenever I want to use module, I don't have to change the working directory?
Is there any way to append additional working directory aside from Python default working directory from within the Python source file? (i.e. not from PATH configuration on Windows)
Is there any way I can link the wrapper with those .dll files dynamically? Meaning that let say the files are copied to another machine and the .dll files are stored in different absolute path directory, the import module would still work?
The point is I want to make this wrapper as portable as possible, across multiple Windows machine.
Thank you.

I found a solution to let module.py find _module.pyd.
Basically, create a new file called module.pth and save it in the same directory as module.py. In this case, the directory is PythonXY/Lib/site-packages/.
Let say you place your _module.pyd inside a directory called _modulelib (PythonXY/Lib/site-packages/_modulelib/), then the content of module.pth should be like this:
_modulelib

Compile python code then place it somewhere else

I have python file, for example, named blah.py, that I would like to have compiled then placed into another folder using cmake. Right now, I am capable of doing this with the following code in my cmake file:
ADD_CUSTOM_TARGET(output ALL /usr/bin/python -m py_compile src/blah.py
COMMAND /bin/mv src/blah.pyc build VERBATIM)
This is on ubuntu 12.04. This code works as intended; the only problem is that the python file is being compiled in the source directory, then being put in the build directory.
However, I can't assume that this src directory will have read AND write privileges, meaning what I need to do is combine these two commands into one (compile the python file and place the compiled python file into my build directory, instead of compiling it in the src directory then moving it)
I'm sure there must be some way I could be using to specify where I would like this compiled code to be placed, but I can't find any. Help would be greatly appreciated! :)
EDIT: This link may have a solution..not sure:
Can compiled bytecode files (.pyc) get generated in different directory?

I was typing out this answer, and then looked at your edited link. This same answer is given in one of the unaccepted answers: https://stackoverflow.com/a/611995/496445
import py_compile
py_compile.compile('/path/to/source/code.py', cfile='/path/to/build/code.pyc')
To call this via a basic shell command you can format it like this:
python -c "import py_compile; py_compile.compile('/path/to/source/code.py', cfile='/path/to/build/code.pyc')"

Python error "ImportError: No module named"

Python is installed in a local directory.
My directory tree looks like this:
(local directory)/site-packages/toolkit/interface.py
My code is in here:
(local directory)/site-packages/toolkit/examples/mountain.py
To run the example, I write python mountain.py, and in the code I have:
from toolkit.interface import interface
And I get the error:
Traceback (most recent call last):
File "mountain.py", line 28, in ?
from toolkit.interface import interface
ImportError: No module named toolkit.interface
I have already checked sys.path and there I have the directory /site-packages. Also, I have the file __init__.py.bin in the toolkit folder to indicate to Python that this is a package. I also have a __init__.py.bin in the examples directory.
I do not know why Python cannot find the file when it is in sys.path. Any ideas? Can it be a permissions problem? Do I need some execution permission?

Based on your comments to orip's post, I guess this is what happened:
You edited __init__.py on windows.
The windows editor added something non-printing, perhaps a carriage-return (end-of-line in Windows is CR/LF; in unix it is LF only), or perhaps a CTRL-Z (windows end-of-file).
You used WinSCP to copy the file to your unix box.
WinSCP thought: "This has something that's not basic text; I'll put a .bin extension to indicate binary data."
The missing __init__.py (now called __init__.py.bin) means python doesn't understand toolkit as a package.
You create __init__.py in the appropriate directory and everything works... ?

Does
(local directory)/site-packages/toolkit
have a __init__.py?
To make import walk through your directories every directory must have a __init__.py file.

I ran into something very similar when I did this exercise in LPTHW; I could never get Python to recognise that I had files in the directory I was calling from. But I was able to get it to work in the end. What I did, and what I recommend, is to try this:
(NOTE: From your initial post, I am assuming you are using an *NIX-based machine and are running things from the command line, so this advice is tailored to that. Since I run Ubuntu, this is what I did)
Change directory (cd) to the directory above the directory where your files are. In this case, you're trying to run the mountain.py file, and trying to call the toolkit.interface.py module, which are in separate directories. In this case, you would go to the directory that contains paths to both those files (or in other words, the closest directory that the paths of both those files share). Which in this case is the toolkit directory.
When you are in the toolkit directory, enter this line of code on your command line:
export PYTHONPATH=.
This sets your PYTHONPATH to ".", which basically means that your PYTHONPATH will now look for any called files within the directory you are currently in, (and more to the point, in the sub-directory branches of the directory you are in. So it doesn't just look in your current directory, but in all the directories that are in your current directory).
After you've set your PYTHONPATH in the step above, run your module from your current directory (the toolkit directory). Python should now find and load the modules you specified.

On *nix, also make sure that PYTHONPATH is configured correctly, especially that it has this format:
.:/usr/local/lib/python
(Mind the .: at the beginning, so that it can search on the current directory, too.)
It may also be in other locations, depending on the version:
.:/usr/lib/python
.:/usr/lib/python2.6
.:/usr/lib/python2.7 and etc.

You are reading this answer says that your __init__.py is in the right place, you have installed all the dependencies and you are still getting the ImportError.
I was facing a similar issue except that my program would run fine when ran using PyCharm but the above error when I would run it from the terminal. After digging further, I found out that PYTHONPATH didn't have the entry for the project directory. So, I set PYTHONPATH per Import statement works on PyCharm but not from terminal:
export PYTHONPATH=$PYTHONPATH:`pwd` (OR your project root directory)
There's another way to do this using sys.path as:
import sys
sys.path.insert(0,'<project directory>') OR
sys.path.append('<project directory>')
You can use insert/append based on the order in which you want your project to be searched.

Using PyCharm (part of the JetBrains suite) you need to define your script directory as Source:
Right Click > Mark Directory as > Sources Root

For me, it was something really stupid. I installed the library using pip3 install but was running my program as python program.py as opposed to python3 program.py.

I solved my own problem, and I will write a summary of the things that were wrong and the solution:
The file needs to be called exactly __init__.py. If the extension is different such as in my case .py.bin then Python cannot move through the directories and then it cannot find the modules. To edit the files you need to use a Linux editor, such as vi or nano. If you use a Windows editor this will write some hidden characters.
Another problem that was affecting it was that I had another Python version installed by the root, so if someone is working with a local installation of python, be sure that the Python installation that is running the programs is the local Python. To check this, just do which python, and see if the executable is the one that is in your local directory. If not, change the path, but be sure that the local Python directory is before than the other Python.

To mark a directory as a package you need a file named __init__.py, does this help?

an easy solution is to install the module using python -m pip install <library-name> instead of pip install <library-name>
you may use sudo in case of admin restrictions

To all those who still have this issue. I believe Pycharm gets confused with imports. For me, when i write 'from namespace import something', the previous line gets underlined in red, signaling that there is an error, but works. However ''from .namespace import something' doesn't get underlined, but also doesn't work.
Try
try:
from namespace import something
except NameError:
from .namespace import something

Yup. You need the directory to contain the __init__.py file, which is the file that initializes the package. Here, have a look at this.
The __init__.py files are required to make Python treat the directories as containing packages; this is done to prevent directories with a common name, such as string, from unintentionally hiding valid modules that occur later on the module search path. In the simplest case, __init__.py can just be an empty file, but it can also execute initialization code for the package or set the __all__ variable, described later.

If you have tried all methods provided above but failed, maybe your module has the same name as a built-in module. Or, a module with the same name existing in a folder that has a high priority in sys.path than your module's.
To debug, say your from foo.bar import baz complaints ImportError: No module named bar. Changing to import foo; print foo, which will show the path of foo. Is it what you expect?
If not, Either rename foo or use absolute imports.

You must have the file __ init__.py in the same directory where it's the file that you are importing.
You can not try to import a file that has the same name and be a file from 2 folders configured on the PYTHONPATH.
eg:
/etc/environment
PYTHONPATH=$PYTHONPATH:/opt/folder1:/opt/folder2
/opt/folder1/foo
/opt/folder2/foo
And, if you are trying to import foo file, python will not know which one you want.
from foo import ... >>> importerror: no module named foo

My two cents:
Spit:
Traceback (most recent call last):
File "bash\bash.py", line 454, in main
import bosh
File "Wrye Bash Launcher.pyw", line 63, in load_module
mod = imp.load_source(fullname,filename+ext,fp)
File "bash\bosh.py", line 69, in <module>
from game.oblivion.RecordGroups import MobWorlds, MobDials, MobICells, \
ImportError: No module named RecordGroups
This confused the hell out of me - went through posts and posts suggesting ugly syspath hacks (as you see my __init__.py were all there). Well turns out that game/oblivion.py and game/oblivion was confusing python
which spit out the rather unhelpful "No module named RecordGroups". I'd be interested in a workaround and/or links documenting this (same name) behavior -> EDIT (2017.01.24) - have a look at What If I Have a Module and a Package With The Same Name? Interestingly normally packages take precedence but apparently our launcher violates this.
EDIT (2015.01.17): I did not mention we use a custom launcher dissected here.

Fixed my issue by writing print (sys.path) and found out that python was using out of date packages despite a clean install. Deleting these made python automatically use the correct packages.

In my case, because I'm using PyCharm and PyCharm create a 'venv' for every project in project folder, but it is only a mini env of python. Although you have installed the libraries you need in Python, but in your custom project 'venv', it is not available. This is the real reason of 'ImportError: No module named xxxxxx' occurred in PyCharm.
To resolve this issue, you must add libraries to your project custom env by these steps:
In PyCharm, from menu 'File'->Settings
In Settings dialog, Project: XXXProject->Project Interpreter
Click "Add" button, it will show you 'Available Packages' dialog
Search your library, click 'Install Package'
Then, all you needed package will be installed in you project custom 'venv' folder.
Enjoy.

Linux: Imported modules are located in /usr/local/lib/python2.7/dist-packages
If you're using a module compiled in C, don't forget to chmod the .so file after sudo setup.py install.
sudo chmod 755 /usr/local/lib/python2.7/dist-packages/*.so

In my case, the problem was I was linking to debug python & boost::Python, which requires that the extension be FooLib_d.pyd, not just FooLib.pyd; renaming the file or updating CMakeLists.txt properties fixed the error.

My problem was that I added the directory with the __init__.py file to PYTHONPATH, when actually I needed to add its parent directory.

For me, running the file as a module helped.
Instead of
python myapp/app.py
using
python -m myapp.app
It's not exactly the same but it might be a better approach in some cases.

If you are using a setup script/utility (e.g. setuptools) to deploy your package, don't forget to add the respective files/modules to the installer.
When supported, use find_packages() or similar to automatically add new packages to the setup script. This will absolutely save you from a headache, especially if you put your project aside for some time and then add something later on.
import setuptools
setuptools.setup(
name="example-pkg",
version="0.0.1",
author="Example Author",
author_email="author#example.com",
description="A small example package",
packages=setuptools.find_packages(),
classifiers=[
"Programming Language :: Python :: 3",
"Operating System :: OS Independent",
],
python_requires='>=3.6',
)
(Example taken from setuptools documentation)

I had the same problem (Python 2.7 Linux), I have found the solution and i would like to share it. In my case i had the structure below:
Booklet
-> __init__.py
-> Booklet.py
-> Question.py
default
-> __init_.py
-> main.py
In 'main.py' I had tried unsuccessfully all the combinations bellow:
from Booklet import Question
from Question import Question
from Booklet.Question import Question
from Booklet.Question import *
import Booklet.Question
# and many othet various combinations ...
The solution was much more simple than I thought. I renamed the folder "Booklet" into "booklet" and that's it. Now Python can import the class Question normally by using in 'main.py' the code:
from booklet.Booklet import Booklet
from booklet.Question import Question
from booklet.Question import AnotherClass
From this I can conclude that Package-Names (folders) like 'booklet' must start from lower-case, else Python confuses it with Class names and Filenames.
Apparently, this was not your problem, but John Fouhy's answer is very good and this thread has almost anything that can cause this issue. So, this is one more thing and I hope that maybe this could help others.

In linux server try dos2unix script_name
(remove all (if there is any) pyc files with command find . -name '*.pyc' -delete)
and re run in the case if you worked on script on windows

In my case, I was using sys.path.insert() to import a local module and was getting module not found from a different library. I had to put sys.path.insert() below the imports that reported module not found. I guess the best practice is to put sys.path.insert() at the bottom of your imports.

I've found that changing the name (via GUI) of aliased folders (Mac) can cause issues with loading modules. If the original folder name is changed, remake the symbolic link. I'm unsure how prevalent this behavior may be, but it was frustrating to debug.

another cause makes this issue
file.py
#!/bin/python
from bs4 import BeautifulSoup
if your default python is pyyhon2
$ file $(which python)
/sbin/python: symbolic link to python2
file.py need python3, for this case(bs4)
you can not execute this module with python2 like this:
$ python file.py
# or
$ file.py
# or
$ file.py # if locate in $PATH
Tow way to fix this error,
# should be to make python3 as default by symlink
$ rm $(which python) && ln -s $(which python3) /usr/bin/python
# or use alias
alias python='/usr/bin.../python3'
or change shebang in file.py to
#!/usr/bin/...python3

After just suffering the same issue I found my resolution was to delete all pyc files from my project, it seems like these cached files were somehow causing this error.
Easiest way I found to do this was to navigate to my project folder in Windows explorer and searching for *.pyc, then selecting all (Ctrl+A) and deleting them (Ctrl+X).
Its possible I could have resolved my issues by just deleting the specific pyc file but I never tried this

I faced the same problem: Import error. In addition the library've been installed 100% correctly. The source of the problem was that on my PC 3 version of python (anaconda packet) have been installed). This is why the library was installed no to the right place. After that I just changed to the proper version of python in the my IDE PyCharm.

I had the same error. It was caused by somebody creating a folder in the same folder as my script, the name of which conflicted with a module I was importing from elsewhere. Instead of importing the external module, it looked inside this folder which obviously didn't contain the expected modules.