python – Import a file from a subdirectory?

I have a file called tester.py, located on /project.

/project has a subdirectory called lib, with a file called BoxTime.py:

/project/tester.py
/project/lib/BoxTime.py

I want to import BoxTime from tester. I have tried this:

import lib.BoxTime

Which resulted:

Traceback (most recent call last):
  File "./tester.py", line 3, in <module>
    import lib.BoxTime
ImportError: No module named lib.BoxTime

Any ideas how to import BoxTime from the subdirectory?

EDIT

The __init__.py was the problem, but don’t forget to refer to BoxTime as lib.BoxTime, or use:

import lib.BoxTime as BT
...
BT.bt_function()

Take a look at the Packages documentation (Section 6.4) here: http://docs.python.org/tutorial/modules.html

In short, you need to put a blank file named

__init__.py

in the “lib” directory.

• Create a subdirectory named lib.
• Create an empty file named lib\__init__.py.

• In lib\BoxTime.py, write a function foo() like this:

  def foo():
      print "foo!"
  
  

• In your client code in the directory above lib, write:

  from lib import BoxTime
  BoxTime.foo()
  
  

• Run your client code. You will get:

  foo!
  
  

Much later — in linux, it would look like this:

% cd ~/tmp
% mkdir lib
% touch lib/__init__.py
% cat > lib/BoxTime.py << EOF
heredoc> def foo():
heredoc>     print "foo!"
heredoc> EOF
% tree lib
lib
├── BoxTime.py
└── __init__.py

0 directories, 2 files
% python 
Python 2.7.6 (default, Mar 22 2014, 22:59:56) 
[GCC 4.8.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from lib import BoxTime
>>> BoxTime.foo()
foo!

You can try inserting it in sys.path:

sys.path.insert(0, './lib')
import BoxTime

I am writing this down because everyone seems to suggest that you have to create a lib directory.

You don’t need to name your sub-directory lib. You can name it anything provided you put an __init__.py into it.

You can do that by entering the following command in a linux shell:

$ touch anything/__init__.py 

So now you have this structure:

$ ls anything/
__init__.py
mylib.py

$ ls
main.py

Then you can import mylib into main.py like this:

from anything import mylib 

mylib.myfun()

You can also import functions and classes like this:

from anything.mylib import MyClass
from anything.mylib import myfun

instance = MyClass()
result = myfun()

Any variable function or class you place inside __init__.py can also be accessed:

import anything

print(anything.myvar)

Or like this:

from anything import myvar

print(myvar)

Does your lib directory contain a __init__.py file?

Python uses __init__.py to determine if a directory is a module.

Try import .lib.BoxTime. For more information read about relative import in PEP 328.

This basically covers all cases (make sure you have __init__.py in relative/path/to/your/lib/folder):

import sys, os
sys.path.append(os.path.dirname(os.path.realpath(__file__)) + "/relative/path/to/your/lib/folder")
import someFileNameWhichIsInTheFolder
...
somefile.foo()

Example:

You have in your project folder:

/root/myproject/app.py

You have in another project folder:

/root/anotherproject/utils.py
/root/anotherproject/__init__.py

You want to use /root/anotherproject/utils.py and call foo function which is in it.

So you write in app.py:

import sys, os
sys.path.append(os.path.dirname(os.path.realpath(__file__)) + "/../anotherproject")
import utils

utils.foo()

Create an empty file __init__.py in subdirectory /lib. And add at the begin of main code

from __future__ import absolute_import 

then

import lib.BoxTime as BT
...
BT.bt_function()

or better

from lib.BoxTime import bt_function
...
bt_function()

Just an addition to these answers.

If you want to import all files from all subdirectories, you can add this to the root of your file.

import sys, os
sys.path.extend([f'./{name}' for name in os.listdir(".") if os.path.isdir(name)])

And then you can simply import files from the subdirectories just as if these files are inside the current directory.

Working example

If I have the following directory with subdirectories in my project…

.
├── a.py
├── b.py
├── c.py
├── subdirectory_a
│   ├── d.py
│   └── e.py
├── subdirectory_b
│   └── f.py
├── subdirectory_c
│   └── g.py
└── subdirectory_d
    └── h.py

I can put the following code inside my a.py file

import sys, os
sys.path.extend([f'./{name}' for name in os.listdir(".") if os.path.isdir(name)])

# And then you can import files just as if these files are inside the current directory

import b
import c
import d
import e
import f
import g
import h

In other words, this code will abstract from which directory the file is coming from.

/project/tester.py

/project/lib/BoxTime.py

create blank file __init__.py down the line till you reach the file

/project/lib/somefolder/BoxTime.py

#lib — needs has two items one __init__.py and a directory named somefolder #somefolder has two items boxtime.py and __init__.py

try this:

from lib import BoxTime