python 从不同文件夹导入 class

Question

my project has folders that are structured like this:

main
 -folder 1
  -file1.py
 -folder 2
  -file2.py

both file1 and file2 having classes. when I try from main.folder1.file1 import class1 it fails, saying "No module named main". What am I doing wrong and how should I import it?

Answer 1

In python you have to declare each folder as a module by adding a file named __init__.py in each directory including the root. This file can be empty.

Answer 2

you can do this if there are one level above.

import sys
sys.path.insert(0,'../folder1')
sys.path.insert(0,'../folder2')
import function1
import function2
....

Once you run the first 3 lines, you are adding those folders to the working directory. You can then import the functions within those files as if they are in the file already.

If the folders are in the same level, do this,

import sys
sys.path.insert(0,'folder1')
sys.path.insert(0,'folder2')
import function1
import function2
....

Answer 3

you have to first create the module by including __init__.py in the root directory which is same in the hierarchy of main folder and also create an __init__.py in other sub folders to make them accessible as modules. Here is an example structure from the official documentation.Note how at each level there is __init__.py you have to include similarly.

package/
    __init__.py
    subpackage1/
        __init__.py
        moduleX.py
        moduleY.py
    subpackage2/
        __init__.py
        moduleZ.py
    moduleA.py

your structure can be like below:

main/
    __init__.py
    folder1/
        __init__.py
        file1.py
    folder2/
        __init__.py
        file2.py

Then you can append the path to the module at the top level like below. You can have it in the __init__.py in the root directory.

sys.path.append(path.dirname(path.dirname(path.abspath( file ))))

Then try accessing like from folder1.file1 import class1 . This should resolve your problem.

To further understand your problem read about modules and how to include relative imports by referring documentation .