Develop Reference

ModuleNotFoundError: I can't import custom modules properly

below the folder structure of my software:
below the code of all the .py files:
run.py:
import modules.module_01.aa as a
a.test()
# test:
if __name__=="__main__":
pass
aa.py (module 1):
import libraries.qq as q
import libraries.zz as z
def test():
q.qq_fun()
z.zz_fun()
print("ciao")
qq.py (library used by aa.py):
def qq_fun():
pass
zz.py (library used by aa.py):
def zz_fun():
pass
my question is really simple, why when I run "run.py" Python say to me:
why "aa.py" can't import the module "qq.py" and "zz.py"? how can I fix this issue?

run.py
In run.py, the Python interpreter thinks you're trying to import module_01.aa from a module named module. To import aa.py, you'll need to add this code to the top of your file, which adds the directory aa.py is in to the system path, and change your import statement to import aa as a.
import sys
sys.path.insert(0, "./modules/module_01/")
aa.py
The same problem occurs in aa.py. To fix the problem in this file, you'll need to add this code to the top of aa.py, which adds the directory qq.py and zz.py are in, and remove the libraries. from both of your import statements.
import sys
sys.path.insert(0, "./modules/module_01/libraries")

How to fix name is not defined in Python

I am running a python project like this:
project
Test.py
COMMON.py
SYSTEM.py
PTEST1
Hello.py
when run the code "Test.py" it will show NameError, I am not sure why?
But if I replaced the "from SYSTEM import *" with "from COMMON import *" in Test.py and PTEST1/Hello.py, it works as expect.
#Test.py is like this:
from SYSTEM import *
myvalue.Hello.printf()
# COMMON.py is like this:
myvalue = lambda: None
from PTEST1.Hello import Hello
myvalue.Hello = Hello
# SYSTEM.py is like this:
from COMMON import *
#PTEST1/Hello.py
from SYSTEM import *
class Hello():
#staticmethod
def printf():
print("Hello1")
print(vars(myvalue))
I expect there is no "NameError" by not changing import code. BTW, my python is 3.6+

Good practice is to give filenames in lowercase.
It looks like you are creating a Python project under project/. Any directory needs to have a file __init__.py in every directory in order for it to be discovered in Python.
You then need to refer to modules by their full name (not relative naming).
So the directory structure should be:
project/
__init__.py
test.py
common.py
system.py
ptest1/
__init__.py
hello.py
Every time you refer to file you should give the full path.
# import everything from hello.py
from project.ptest1.hello import *
# import everything from common.py
from project.common import *
# import everything from system.py
from project.system import *

Import all files in current directory

I have just started a python project. The directory structure is as follows:
/algorithms
----/__init__.py
----/linkedlist
--------/__init__.py
--------/file1.py
--------/file2.py
/tests
----/test_linkedlist
You can also check the Github repository.
In each of the sub folders under algorithms, in the __init__ file I am including the following for all the files one by one:
from .file1 import *
from .file2 import *
And so on.
The task that I am trying to achieve is running all tests together using the query:
python3 -m unittest discover tests
Each file in the tests directory starts as follows:
from algorithms.linkedlist import *
import unittest
Right now if I want to add a new file to the linkedlist directory, I create the file and then add another from .filename import * in the __init__ file.
How do I write a script in the __init__ file so that each time I create a new file, I do not have to manually insert the import command?

So the __init__ is in the same folder? As the docs say The import statement is syntactic sugar for the __import__ function.
So we can use:
import importlib
import glob
for file in glob.iglob('*.py'):
importlib.__import__(file)
Some reasons why this does not work:
You want to load the functions in the module - the import * from syntax. With this code you can only run file1.test.
You run the script loading from another directory, which confuses glob. We have to specify the actual working directory.
__import__ prefers to know the module name.
To find the solution I combine the import * from function from this answer with pkgutil.walk_packages from this blog.
import importlib
import pkgutil
def custom_import_all(module_name):
""" Use to dynamically execute from module_name import * """
# get a handle on the module
mdl = importlib.import_module(module_name)
# is there an __all__? if so respect it
if "__all__" in mdl.__dict__:
names = mdl.__dict__["__all__"]
else:
# otherwise we import all names that don't begin with _
names = [x for x in mdl.__dict__ if not x.startswith("_")]
# now drag them in
globals().update({k: getattr(mdl, k) for k in names})
__path__ = pkgutil.extend_path(__path__, __name__)
for importer, modname, ispkg in pkgutil.walk_packages(path=__path__, prefix=__name__+'.'):
custom_import_all(modname)

Python 3 relative import full module

I'm trying to make some code Python 3 compatible. To my understanding, in Python 3, importing a module from the same package must be relative. So if this is the directory structure:
/package
/modA
/modB
there's a lot of existing code that looks like this (in modA):
import modB
modB.some_function()
Is there a way to change the imports so I can keep calling the methods/properties the same way?
I know you can do this:
from .modB import some_function
some_function()
But I'd like to avoid changing all the calls if possible. When I call it like so:
import .modB
it gives an error

The syntax to relative-import a module modB from the same package would be
from . import modB

This extends the answer of #user2357112
In order to work in both python2 and python3 you have to:
Structure:
/package
__init__.py
modA.py
modB.py
content of __init__.py
from . import modA, modB
content of modA.py
# from . import modB ## works in py3 but not in py2
def testA():
""" call a function from modB """
from . import modB
modB.printB()
def printA():
print('I am in modA')
content of modB.py
# from . import modA ## works in py3 not in py2
def testB():
""" call a function from modA """
from . import modA
modA.printA()
def printB():
print('I am in modB')
Then you can do:
import package
package.modA.testA()
package.modB.testB()

you can use importlib
import importlib
and then
modB = importlib.import_module('package.modB')
... granted it's not optimal but still a working option if you're having persistent issues with relative path imports (never run into issues on POSIX and OSx, but on NT platform I have)

Import classes from child directory python

I've been trying to import some python classes which are defined in a child directory. The directory structure is as follows:
workspace/
__init__.py
main.py
checker/
__init__.py
baseChecker.py
gChecker.py
The baseChecker.py looks similar to:
import urllib
class BaseChecker(object):
# SOME METHODS HERE
The gChecker.py file:
import baseChecker # should import baseChecker.py
class GChecker(BaseChecker): # gives a TypeError: Error when calling the metaclass bases
# SOME METHODS WHICH USE URLLIB
And finally the main.py file:
import ?????
gChecker = GChecker()
gChecker.someStuff() # which uses urllib
My intention is to be able to run main.py file and call instantiate the classes under the checker/ directory. But I would like to avoid importing urllib from each file (if it is possible).
Note that both the __init__.py are empty files.
I have already tried calling from checker.gChecker import GChecker in main.py but a ImportError: No module named checker.gChecker shows.

In the posted code, in gChecker.py, you need to do
from baseChecker import BaseChecker
instead of import baseChecker
Otherwise you get
NameError: name 'BaseChecker' is not defined
Also with the mentioned folders structure you don't need checker module to be in the PYTHONPATH in order to be visible by main.py
Then in main.y you can do:
from checker import gChecker.GChecker