I'm trying to test my code with Pytest framework, but for some reason I don't succeed importing my own code...
You have to import your code from the top module, like this:
from se2pdf.se2pdf import changeFileExtensionToPDF
the first se2pdf is the folder name and the second your file name. If it doesn't work, make sure there is a _init_.py file in the modules.
Let's say there are two files - mask.py and main.py.
mask.py has some function that I'm importing into main.py.
So if that function in mask.py which I'm importing has dependency like "os", where should I import os - in mask.py or main.py.
Let us consider a scenario as you have stated by using two files mask.py and main.py.
mask.py
import os
def some_function():
os.environ['a_url'] = "something.com" # using dependency as you mentioned
main.py
from mask import some_function
# do something with the function
Now, coming to your query, if you use import os in main.py but not in mask.py, you will get NameError in mask.py saying:
NameError: name 'os' is not defined
This is because you need to import any dependency in the same file where it is used. Also, if both of your file uses this dependency, you need to import it in both the files.
Hope this clarifies your query.
I have been struggling to figure out how to organize my code effectively with many modules of various types. I have a three layered folder system. The parent directory contains the main.py file which imports and runs the main code. The modules are in a subfolder called lib, and different modules are placed in further subfolders. However, when I import one module from a subfolder, that module itself fails to import modules in the same sub directory. Sorry if this is a bad question, but I cannot figure out why the import statement isn't working, and I have looked at google and stack overflow and have not found any similar problem. All advice is welcome.
Parent Directory
---->lib
|--->module_group
|module_one.py(that tries but fails to import module_one)
|module_two.py
|main.py
In main I run
from lib.module_group.module_one import Module_One
Which works until an error is handled saying that there is no such module as module two. However, when I run module_one by itself, it works fine with the following import statement.
from module_two import Module_Two
Set PYTHONPATH to the directory you want to act as your root. For example, if you want to use the following code:
from lib.module_group.module_one import Module_One
Then set PYTHONPATH to the directorying containing lib. For example:
lib/module_group/module_one.py:
from lib.module_group.module_two import Module_Two
lib/module_group/module_two.py:
class Module_Two:
print('Loaded Module_Two')
Then, to run module_one.py directly and still enable it to use lib.module_group.module_two to load Module_Two, use something like:
$ PYTHONPATH="${PWD}:${PYTHONPATH}" python3 lib/module_group/module_one.py
Loaded Module_Two
I'm in the process of learning how to package a python library using the official guide. I've started cloning the minimal sample package suggested in the guide here. I've then added the file my_module.py inside the folder sampleproject storing a simple power function. Another function is also stored in /sampleproject/sampleproject/__init__.py. The resulting structure of the library is the following
Finally, I've used pip to successfully install the package in the interpreter. The only thing left is to make sure that I'm able to run the functions stored in the subfolder sampleproject.
import sampleproject
sampleproject.main()
# Output
"Call your main application code here"
This is great. The package is able to run the function in __init__.py. However, the package is not able to find module.py:
import sampleproject
sampleproject.module
# Output
AttributeError: module 'sampleproject' has no attribute 'module'
I've tried to add __init__.py in the main folder and to change the settings in entry_points in setup.py without success. What should I let sampleproject to be able to find the function in module.py?
Your sampleproject.module is a function you would like to execute?
In this case, do as for the sampleproject, add () to execute it:
sampleproject.module()
Otherwise, you can import your package like this:
import sampleproject.module
or:
from sampleproject import module
To be clearer, you would have to import module in your sampleproject __init__.py. Then, when you want to use the package, import it (is some py file at root):
import sampleproject # is enough as it's going to import everything you stated in __init__.py
After that, you can start to use what's in the package you imported with maybe module() if you have a function called module in your package.
init.py discussions
it seems,
you are in sampleproject->module.py
so you need to try,
from sampleproject import module
Currently trying to work in Python3 and use absolute imports to import one module into another but I get the error ModuleNotFoundError: No module named '__main__.moduleB'; '__main__' is not a package. Consider this project structure:
proj
__init__.py3 (empty)
moduleA.py3
moduleB.py3
moduleA.py3
from .moduleB import ModuleB
ModuleB.hello()
moduleB.py3
class ModuleB:
def hello():
print("hello world")
Then running python3 moduleA.py3 gives the error. What needs to be changed here?
.moduleB is a relative import. Relative only works when the parent module is imported or loaded first. That means you need to have proj imported somewhere in your current runtime environment. When you are are using command python3 moduleA.py3, it is getting no chance to import parent module. You can:
from proj.moduleB import moduleB OR
You can create another script, let's say run.py, to invoke from proj import moduleA
Good luck with your journey to the awesome land of Python.
Foreword
I'm developing a project which in fact is a Python package that can be installed through pip, but it also exposes a command line interface. I don't have problems running my project after installing it with pip install ., but hey, who does this every time after changing something in one of the project files? I needed to run the whole thing through simple python mypackage/main.py.
/my-project
- README.md
- setup.py
/mypackage
- __init__.py
- main.py
- common.py
The different faces of the same problem
I tried importing a few functions in main.py from my common.py module. I tried different configurations that gave different errors, and I want to share with you with my observations and leave a quick note for future me as well.
Relative import
The first what I tried was a relative import:
from .common import my_func
I ran my application with simple: python mypackage/main.py. Unfortunately this gave the following error:
ModuleNotFoundError: No module named '__main__.common'; '__main__' is not a package
The cause of this problem is that the main.py was executed directly by python command, thus becoming the main module named __main__. If we connect this information with the relative import we used, we get what we have in the error message: __main__.common. This is explained in the Python documentation:
Note that relative imports are based on the name of the current module. Since the name of the main module is always __main__, modules intended for use as the main module of a Python application must always use absolute imports.
When I installed my package with pip install . and then ran it, it worked perfectly fine. I was also able to import mypackage.main module in a Python console. So it looks like there's a problem only with running it directly.
Absolute import
Let's follow the advise from the documentation and change the import statement to something different:
from common import my_func
If we now try to run this as before: python mypackage/main.py, then it works as expected! But, there's a caveat when you, like me, develop something that need to work as a standalone command line tool after installing it with pip. I installed my package with pip install . and then tried to run it...
ModuleNotFoundError: No module named 'common'
What's worse, when I opened a Python console, and tried to import the main module manually (import mypackage.main), then I got the same error as above. The reason for that is simple: common is no longer a relative import, so Python tries to find it in installed packages. We don't have such package, that's why it fails.
The solution with an absolute import works well only when you create a typical Python app that is executed with a python command.
Import with a package name
There is also a third possibility to import the common module:
from mypackage.common import my_func
This is not very different from the relative import approach, as long as we do it from the context of mypackage. And again, trying to run this with python mypackage/main.py ends similar:
ModuleNotFoundError: No module named 'mypackage'
How irritating that could be, the interpreter is right, you don't have such package installed.
The solution
For simple Python apps
Just use absolute imports (without the dot), and everything will be fine.
For installable Python apps in development
Use relative imports, or imports with a package name on the beginning, because you need them like this when your app is installed. When it comes to running such module in development, Python can be executed with the -m option:
-m mod : run library module as a script (terminates option list)
So instead of python mypackage/main.py, do it like this: python -m mypackage.main.
In addition to md-sabuj-sarker's answer, there is a really good example in the Python modules documentation.
This is what the docs say about intra-package-references:
Note that relative imports are based on the name of the current module. Since the name of the main module is always "__main__", modules intended for use as the main module of a Python application must always use absolute imports.
If you run python3 moduleA.py3, moduleA is used as the main module, so using the absolute import looks like the right thing to do.
However, beware that this absolute import (from package.module import something) fails if, for some reason, the package contains a module file with the same name as the package (at least, on my Python 3.7). So, for example, it would fail if you have (using the OP's example):
proj/
__init__.py (empty)
proj.py (same name as package)
moduleA.py
moduleB.py
in which case you would get:
ModuleNotFoundError: No module named 'proj.moduleB'; 'proj' is not a package
Alternatively, you could remove the . in from .moduleB import, as suggested here and here, which seems to work, although my PyCharm (2018.2.4) marks this as an "Unresolved reference" and fails to autocomplete.
Maybe you can do this before importing the moduleļ¼
moduleA.py3
import os
import sys
sys.path.append(os.path.dirname(os.path.abspath(__file__)))
from moduleB import ModuleB
ModuleB.hello()
Add the current directory to the environment directory
Just rename the file from where you run the app to main.py:
from app import app
if __name__ == '__main__':
app.run()
import os
import sys
sys.path.append(os.path.dirname(os.path.abspath(__file__)))
will solve the issue of import path issue.