从相对路径导入模块

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.

Assuming that both your directories are real Python packages (do have the __init__.py file inside them), here is a safe solution for inclusion of modules relatively to the location of the script.

I assume that you want to do this, because you need to include a set of modules with your script. I use this in production in several products and works in many special scenarios like: scripts called from another directory or executed with python execute instead of opening a new interpreter.

 import os, sys, inspect
 # realpath() will make your script run, even if you symlink it :)
 cmd_folder = os.path.realpath(os.path.abspath(os.path.split(inspect.getfile( inspect.currentframe() ))[0]))
 if cmd_folder not in sys.path:
     sys.path.insert(0, cmd_folder)

 # Use this if you want to include modules from a subfolder
 cmd_subfolder = os.path.realpath(os.path.abspath(os.path.join(os.path.split(inspect.getfile( inspect.currentframe() ))[0],"subfolder")))
 if cmd_subfolder not in sys.path:
     sys.path.insert(0, cmd_subfolder)

 # Info:
 # cmd_folder = os.path.dirname(os.path.abspath(__file__)) # DO NOT USE __file__ !!!
 # __file__ fails if the script is called in different ways on Windows.
 # __file__ fails if someone does os.chdir() before.
 # sys.argv[0] also fails, because it doesn't not always contains the path.

As a bonus, this approach does let you force Python to use your module instead of the ones installed on the system.

Warning! I don’t really know what is happening when current module is inside an egg file. It probably fails too.

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

You could also add the subdirectory to your Python path so that it imports as a normal script.

import sys
sys.path.insert(0, <path to dirFoo>)
import Bar

import os
import sys
lib_path = os.path.abspath(os.path.join(__file__, '..', '..', '..', 'lib'))
sys.path.append(lib_path)

import mymodule

Just do simple things to import the .py file from a different folder.

Let’s say you have a directory like:

lib/abc.py

Then just keep an empty file in lib folder as named

__init__.py

And then use

from lib.abc import <Your Module name>

Keep the __init__.py file in every folder of the hierarchy of the import module.

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.

The easiest method is to use sys.path.append().

However, you may be also interested in the imp module. It provides access to internal import functions.

# mod_name is the filename without the .py/.pyc extention
py_mod = imp.load_source(mod_name,filename_path) # Loads .py file
py_mod = imp.load_compiled(mod_name,filename_path) # Loads .pyc file 

This can be used to load modules dynamically when you don’t know a module’s name.

I’ve used this in the past to create a plugin type interface to an application, where the user would write a script with application specific functions, and just drop thier script in a specific directory.

Also, these functions may be useful:

imp.find_module(name[, path])
imp.load_module(name, file, pathname, description)

This is the relevant PEP:

http://www.python.org/dev/peps/pep-0328/

In particular, presuming dirFoo is a directory up from dirBar…

In dirFoo\Foo.py:

from ..dirBar import Bar

The easiest way without any modification to your script is to set PYTHONPATH environment variable. Because sys.path is initialized from these locations:

1. The directory containing the input script (or the current directory).
2. PYTHONPATH (a list of directory names, with the same syntax as the shell variable PATH).
3. The installation-dependent default.

Just run:

export PYTHONPATH=/absolute/path/to/your/module

You sys.path will contains above path, as show below:

print sys.path

['', '/absolute/path/to/your/module', '/usr/lib/python2.7', '/usr/lib/python2.7/plat-linux2', '/usr/lib/python2.7/lib-tk', '/usr/lib/python2.7/lib-old', '/usr/lib/python2.7/lib-dynload', '/usr/local/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages/PIL', '/usr/lib/python2.7/dist-packages/gst-0.10', '/usr/lib/python2.7/dist-packages/gtk-2.0', '/usr/lib/pymodules/python2.7', '/usr/lib/python2.7/dist-packages/ubuntu-sso-client', '/usr/lib/python2.7/dist-packages/ubuntuone-client', '/usr/lib/python2.7/dist-packages/ubuntuone-control-panel', '/usr/lib/python2.7/dist-packages/ubuntuone-couch', '/usr/lib/python2.7/dist-packages/ubuntuone-installer', '/usr/lib/python2.7/dist-packages/ubuntuone-storage-protocol']

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.

The quick-and-dirty way for Linux users

If you are just tinkering around and don’t care about deployment issues, you can use a symbolic link (assuming your filesystem supports it) to make the module or package directly visible in the folder of the requesting module.

ln -s (path)/module_name.py

or

ln -s (path)/package_name

Note: A “module” is any file with a .py extension and a “package” is any folder that contains the file __init__.py (which can be an empty file). From a usage standpoint, modules and packages are identical — both expose their contained “definitions and statements” as requested via the import command.

See: http://docs.python.org/2/tutorial/modules.html

from .dirBar import Bar

instead of:

from dirBar import Bar

just in case there could be another dirBar installed and confuse a foo.py reader.

For this case to import Bar.py into Foo.py, first I’d turn these folders into Python packages like so:

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

Then I would do it like this in Foo.py:

from .dirBar import Bar

If I wanted the namespacing to look like Bar.whatever, or

from . import dirBar

If I wanted the namespacing dirBar.Bar.whatever. This second case is useful if you have more modules under the dirBar package.

Add an __init__.py file:

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

Then add this code to the start of Foo.py:

import sys
sys.path.append('dirBar')
import Bar

Relative sys.path example:

# /lib/my_module.py
# /src/test.py


if __name__ == '__main__' and __package__ is None:
    sys.path.append(os.path.abspath(os.path.join(os.path.dirname(__file__), '../lib')))
import my_module

Based on this answer.

Well, as you mention, usually you want to have access to a folder with your modules relative to where your main script is run, so you just import them.

Solution:

I have the script in D:/Books/MyBooks.py and some modules (like oldies.py). I need to import from subdirectory D:/Books/includes:

import sys,site
site.addsitedir(sys.path[0] + '\\includes')
print (sys.path)  # Just verify it is there
import oldies

Place a print('done') in oldies.py, so you verify everything is going OK. This way always works because by the Python definition sys.path as initialized upon program startup, the first item of this list, path[0], is the directory containing the script that was used to invoke the Python interpreter.

If the script directory is not available (e.g. if the interpreter is invoked interactively or if the script is read from standard input), path[0] is the empty string, which directs Python to search modules in the current directory first. Notice that the script directory is inserted before the entries inserted as a result of PYTHONPATH.

Simply you can use: from Desktop.filename import something

Example:

given that the file is name test.py in directory Users/user/Desktop , and will import everthing.

the code:

from Desktop.test import *

But make sure you make an empty file called “__init__.py” in that directory

Another solution would be to install the py-require package and then use the following in Foo.py

import require
Bar = require('./dirBar/Bar')

Here’s a way to import a file from one level above, using the relative path.

Basically, just move the working directory up a level (or any relative location), add that to your path, then move the working directory back where it started.

#to import from one level above:
cwd = os.getcwd()
os.chdir("..")
below_path =  os.getcwd()
sys.path.append(below_path)
os.chdir(cwd)

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.

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

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

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.