I have a Python project in which I have the following folder structure:
> root
> download_module
> __init__.py
> downloadProcess.py
> sharedFunctions.py
> someHelper.py
> useSharedFunction.py
The download_module/__init__.py has the following code:
from .sharedFunctions import stringArgumentToDate
from .downloadProcess import downloadProcessMethod
The sharedFunctions.py file contains the following function:
def stringArgumentToDate(arg):
dateformat = "%m/%d/%Y"
date = None
if arg.isnumeric():
date = datetime.fromtimestamp(int(arg))
if date == None:
date = datetime.strptime(arg, dateformat)
return date
Then on the useSharedFunction.py I try to import the shared function and use it like this.
from download_module import stringArgumentToDate
from download_module import downloadProcessMethod
def main():
arg = '03/14/2022'
dateArg = stringArgumentToDate(arg)
if __name__ == '__main__':
main()
When I try to run this by using python3 useSharedFunction.py I got the following error:
Traceback (most recent call last):
File "useSharedFunction.py", line 4, in <module>
from download_module import stringArgumentToDate
File "/Users/jacobo/Documents/project/download_module/__init__.py", line 2, in <module>
from .download_module import downloadAndProcessMethod
File "/Users/jacobo/Documents/project/download_module/downloadProcess.py", line 10, in <module>
from sharedFunctions import stringArgumentToDate, otherFunction
ModuleNotFoundError: No module named 'sharedFunctions'
I do believe the error is in downloadProcess since at the beggining of the file we got this import:
from sharedFunctions import stringArgumentToDate, otherFunction
from someHelper import Helper
Which refers to sibling files.
However I'm unsure what will be a proper fix to allow to run the downloadProcess.py main independently but also, being able to call it one of its method from a root or any other file out of the module.
Consider this structure:
┬ module
| ├ __init__.py
| ├ importing_submodule.py
| └ some_submodule.py
├ __main__.py
├ some_submodule.py
└ module_in_parent_dir.py
with content:
__main__.py
import module
/module/__init__.py
from . import importing_submodule
/module/importing_submodule.py
from some_submodule import SomeClass
/module/some_submodule.py
print("you imported from module")
class SomeClass:
pass
/some_submodule.py
print("you imported from root")
class SomeClass:
pass
/module_in_parent_dir.py
class SomeOtherClass:
pass
How sibling import works
(skip this section if you know already)
Now lets run __main__.py and it will say "you imported from root".
But if we change code a bit..
/module/importing_submodule.py
from module.some_submodule import SomeClass
It now says "You imported from module" as we wanted, probably with scary red line in IDE saying "Unresolved reference" if you didn't config working directory in IDE.
How this happen is simple: script root(Current working directory) is decided by main script(first script that's running), and python uses namespaces.
Python's import system uses 2 import method, and for convenience let's call it absolute import and relative import.
Absolute import: Import from dir listed in sys.path and current working directory
Relative import: Import relative to the very script that called import
And what decide the behavior is whether we use . at start of module name or not.
Since we imported by from some_submodule without preceeding dot, python take it as 'Absolute import'(the term we decided earlier).
And then when we also specified module name like from module.some_submodule python looks for module in path list or in current working directory.
Of course, this is never a good idea; script root can change via calls like os.chdir() then submodules inside module folder may get lost.
Therefore, the best practices for sibling import is using relative import inside module folder.
/module/importing_submodule.py
from .some_submodule import SomeClass
Making script that work in both way
To make submodule import it's siblings when running as main script, yet still work as submodule when imported by other script, then use try - except and look for ImportError.
For importing_submodule.py as an example:
/module/importing_submodule.py
try:
from .some_submodule import SomeClass
except ImportError:
# attempted relative import with no known parent package
# because this is running as main script, there's no parent package.
from some_submodule import SomeClass
Importing modules from parent directory is a bit more tricky.
Since submodule is now main script, relative import to parent level directory doesn't work.
So we need to add the parent directory to sys.path, when the script is running as main script.
/module/importing_submodule.py
try:
from .some_submodule import SomeClass
except ImportError:
# attempted relative import with no known parent package
# because this is running as main script, there's no parent package.
from some_submodule import SomeClass
# now since we don't have parent package, we just append the path.
from sys import path
import pathlib
path.append(pathlib.Path(__file__).parent.parent.as_posix())
print("Importing module_in_parent_dir from sys.path")
else:
print("Importing module_in_parent_dir from working directory")
# Now either case we have parent directory of `module_in_parent_dir`
# in working dir or path, we can import it
# might need to suppress false IDE warning this case.
# noinspection PyUnresolvedReferences
from module_in_parent_dir import SomeOtherClass
Output:
"C:\Program Files\Python310\python.exe" .../module/importing_module.py
you imported from module
Importing module_in_parent_dir from sys.path
Process finished with exit code 0
"C:\Program Files\Python310\python.exe" .../__main__.py
you imported from module
Importing module_in_parent_dir from working directory
Process finished with exit code 0
Related
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")
I am trying to import main1.py file in views.py of my django app.
But unable to import it.
Moreover location of my main file and sub-dependent file also lies at the view.py folder location.
I have tried with following options
1 import main
with this error is : No module found with name main
2 from .app_name import main
using this error is : import * only allowed at module level
folder structure is
The name of the file is main1.py, but you are trying to import main.py.
Try:
from app_name import main1 # Absolute import.
from . import main1 # Explicit relative import.
import main1 # Implicit relative import. Won't work in Python3.
I know how to import a package or module, but I meet a quite strange problem.
If I run swmm5_extend_function/example.py, everything is fine. However, when I run example.py, errors occur:
Traceback (most recent call last):
File "example.py", line 2, in <module>
from swmm5_extend_function.Swmm5Extend import SWMM5ReadInp
File "C:\project\swmm5_extend_function\Swmm5Extend.py", line 1, in <module>
import swig.SWMM5ReadInpFile as swmm
ModuleNotFoundError: No module named 'swig'
Here is my project structure:
project/
-- example.py
-- ......
-- swmm5_extend_function/
-- __init__.py
-- example.py
-- Swmm5Extend.py
-- swig/
-- __init__.py
-- SWMM5ReadInpFile.py
-- ....
Here is code of each .py file:
swmm5_extend_function/Swmm5Extend.py
import swig.SWMM5ReadInpFile as swmm
class SWMM5ReadInp(object):
pass
swmm5_extend_function/example.py
from Swmm5Extend import SWMM5ReadInp
example.py
from swmm5_extend_function.Swmm5Extend import SWMM5ReadInp
I want to know why this strange error happens.
For a better explanation, I've created the following folder structure:
test/
-- __init__.py
-- greeter.py # Greets in German
-- subfolder/
-- __init__.py
-- greeter.py # Greets in Italian
-- test.py
-- deepfolder/
-- __init__.py
-- greeter.py # Greets in France
As you may notice, we have 3 files with the same name, each one greets in a different language using a function with the same name. The only function in a greeter.py file is:
def says():
print("Hello World!")
IMPORT FROM THE SAME FOLDER
If from test.py file we import greeter and run the says function, we'll have:
import greeter as greeter
greeter.says()
Output:
Buongiorno Mondo! # Italian output
IMPORT FROM A SUBFOLDER
But what if we want to import from a subfolder?
To import from a subfolder (i.e., deepfolder/), we simply add an empty __init__.py file into the folder, then we can specify the path in the import:
import deepfolder.greeter as greeter
greeter.says()
Output:
Bonjour le Monde! # France output
IMPORT FROM A PARENT FOLDER
At last, you may want to import from a parent folder.
You should try to have your main running file at the top of the folder tree, but things happens and you find yourself looking to import a module from a parent folder.
For doing this, you need to add the parent folder to the sys.path:
import sys
sys.path.append("/path/to/dir")
from test import greeter as greeter
greeter.says()
Output:
Guten Morgen Welt! # German output
Importing scripts and modules isn't really the most pythonic way to solve things, you may want to have a look on Python's documentation about packages.
TL;DR
In your project/example.py use
import swmm5_extend_function.swig.SWMM5ReadInpFile as swmm
instead of
import swig.SWMM5ReadInpFile as swmm
I have 4 files in my project:
project/__init__.py
project/app.py
project/mod_x.py
project/mod_y.py
In mod_x.py I have a class (e.g. ModX)
In mod_y.py I have just one function.
I import modules from app.py as follows:
from .mod_x import ModX
import .mod_y
I get an error:
ImportError: No module named 'mod_y'
Before I created init.py I didn't have that kind of problems (of course, I dont put "." before module name).
How to import module which doesn't have the class inside in Python3 with init.py file inside the current directory?
Relative imports are only available for from...import syntax.
You could import that function this way:
from .mod_y import FUNCTION_NAME
Module could be imported this way:
from . import mod_y
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