Import a module from a relative path

Question

How do I import a Python module given its relative path?

For example, if dirFoo contains Foo.py and dirBar, and dirBar contains Bar.py, how do I import Bar.py into Foo.py?

Here's a visual representation:

dirFoo\
    Foo.py
    dirBar\
        Bar.py

Foo wishes to include Bar, but restructuring the folder hierarchy is not an option.

Answer 1

Call me overly cautious, but I like to make mine more portable because it's unsafe to assume that files will always be in the same place on every computer. Personally I have the code look up the file path first. I use Linux so mine would look like this:

import os, sys
from subprocess import Popen, PIPE
try:
    path = Popen("find / -name 'file' -type f", shell=True, stdout=PIPE).stdout.read().splitlines()[0]
    if not sys.path.__contains__(path):
        sys.path.append(path)
except IndexError:
    raise RuntimeError("You must have FILE to run this program!")

That is of course unless you plan to package these together. But if that's the case you don't really need two separate files anyway.

Answer 2

If you structure your project this way:

src\
  __init__.py
  main.py
  dirFoo\
    __init__.py
    Foo.py
  dirBar\
    __init__.py
    Bar.py

Then from Foo.py you should be able to do:

import dirFoo.Foo

Or:

from dirFoo.Foo import FooObject

Per Tom's comment, this does require that the src folder is accessible either via site_packages or your search path. Also, as he mentions, __init__.py is implicitly imported when you first import a module in that package/directory. Typically __init__.py is simply an empty file.

Answer 3

This also works, and is much simpler than anything with the sys module:

with open("C:/yourpath/foobar.py") as f:
    eval(f.read())

Answer 4

I'm not experienced about python, so if there is any wrong in my words, just tell me. If your file hierarchy arranged like this:

project\
    module_1.py 
    module_2.py

module_1.py defines a function called func_1(), module_2.py:

from module_1 import func_1

def func_2():
    func_1()

if __name__ == '__main__':
    func_2()

and you run python module_2.py in cmd, it will do run what func_1() defines. That's usually how we import same hierarchy files. But when you write from .module_1 import func_1 in module_2.py, python interpreter will say No module named '__main__.module_1'; '__main__' is not a package. So to fix this, we just keep the change we just make, and move both of the module to a package, and make a third module as a caller to run module_2.py.

project\
    package_1\
        module_1.py
        module_2.py
    main.py

main.py:

from package_1.module_2 import func_2

def func_3():
    func_2()

if __name__ == '__main__':
    func_3()

But the reason we add a . before module_1 in module_2.py is that if we don't do that and run main.py, python interpreter will say No module named 'module_1', that's a little tricky, module_1.py is right beside module_2.py. Now I let func_1() in module_1.py do something:

def func_1():
    print(__name__)

that __name__ records who calls func_1. Now we keep the . before module_1 , run main.py, it will print package_1.module_1, not module_1. It indicates that the one who calls func_1() is at the same hierarchy as main.py, the . imply that module_1 is at the same hierarchy as module_2.py itself. So if there isn't a dot, main.py will recognize module_1 at the same hierarchy as itself, it can recognize package_1, but not what "under" it.

Now let's make it a bit complicated. You have a config.ini and a module defines a function to read it at the same hierarchy as 'main.py'.

project\
    package_1\
        module_1.py
        module_2.py
    config.py
    config.ini
    main.py

And for some unavoidable reason, you have to call it with module_2.py, so it has to import from upper hierarchy.module_2.py:

 import ..config
 pass

Two dots means import from upper hierarchy (three dots access upper than upper,and so on). Now we run main.py, the interpreter will say:ValueError:attempted relative import beyond top-level package. The "top-level package" at here is main.py. Just because config.py is beside main.py, they are at same hierarchy, config.py isn't "under" main.py, or it isn't "leaded" by main.py, so it is beyond main.py. To fix this, the simplest way is:

project\
    package_1\
        module_1.py
        module_2.py
    config.py
    config.ini
main.py

I think that is coincide with the principle of arrange project file hierarchy, you should arrange modules with different function in different folders, and just leave a top caller in the outside, and you can import how ever you want.

Answer 5

Be sure that dirBar has the __init__.py file -- this makes a directory into a Python package.

Answer 6

In my opinion the best choice is to put __ init __.py in the folder and call the file with

from dirBar.Bar import *

It is not recommended to use sys.path.append() because something might gone wrong if you use the same file name as the existing python package. I haven't test that but that will be ambiguous.