如何导入其他Python文件？

How do I import other files in Python?

1. How exactly can I import a specific python file like import file.py?
2. How can I import a folder instead of a specific file?
3. I want to load a Python file dynamically at runtime, based on user input.
4. I want to know how to load just one specific part from the file.

For example, in main.py I have:

from extra import * 

Although this gives me all the definitions in extra.py, when maybe all I want is a single definition:

def gap():
    print
    print

What do I add to the import statement to just get gap from extra.py?

importlib was added to Python 3 to programmatically import a module. It is just a wrapper around __import__, see the docs.

import importlib

moduleName = input('Enter module name:')
importlib.import_module(moduleName)

Note: the .py extension should be removed from moduleName. The function also defines a package argument for relative imports.

Update: Answer below is outdated. Use the more recent alternative above.

1. Just import file without the ‘.py’ extension.

2. You can mark a folder as a package, by adding an empty file named __init__.py.

3. You can use the __import__ function. It takes the module name as a string. (Again: module name without the ‘.py’ extension.)

   pmName = input('Enter module name:')
   pm = __import__(pmName)
   print(dir(pm))
   

   Type help(__import__) for more details.

There are many ways to import a python file, all with their pros and cons.

Don’t just hastily pick the first import strategy that works for you or else you’ll have to rewrite the codebase later on when you find it doesn’t meet your needs.

I’ll start out explaining the easiest example #1, then I’ll move toward the most professional and robust example #7

Example 1, Import a python module with python interpreter:

1. Put this in /home/el/foo/fox.py:

   def what_does_the_fox_say():
     print("vixens cry")
   

2. Get into the python interpreter:

   el@apollo:/home/el/foo$ python
   Python 2.7.3 (default, Sep 26 2013, 20:03:06) 
   >>> import fox
   >>> fox.what_does_the_fox_say()
   vixens cry
   >>> 
   

   You imported fox through the python interpreter, invoked the python function what_does_the_fox_say() from within fox.py.

Example 2, Use execfile or (exec in Python 3) in a script to execute the other python file in place:

1. Put this in /home/el/foo2/mylib.py:

   def moobar():
     print("hi")
   

2. Put this in /home/el/foo2/main.py:

   execfile("/home/el/foo2/mylib.py")
   moobar()
   

3. run the file:

   el@apollo:/home/el/foo$ python main.py
   hi
   

   The function moobar was imported from mylib.py and made available in main.py

Example 3, Use from … import … functionality:

1. Put this in /home/el/foo3/chekov.py:

   def question():
     print "where are the nuclear wessels?"
   

2. Put this in /home/el/foo3/main.py:

   from chekov import question
   question()
   

3. Run it like this:

   el@apollo:/home/el/foo3$ python main.py 
   where are the nuclear wessels?
   

   If you defined other functions in chekov.py, they would not be available unless you import *

Example 4, Import riaa.py if it’s in a different file location from where it is imported

1. Put this in /home/el/foo4/stuff/riaa.py:

   def watchout():
     print "computers are transforming into a noose and a yoke for humans"
   

2. Put this in /home/el/foo4/main.py:

   import sys 
   import os
   sys.path.append(os.path.abspath("/home/el/foo4/stuff"))
   from riaa import *
   watchout()
   

3. Run it:

   el@apollo:/home/el/foo4$ python main.py 
   computers are transforming into a noose and a yoke for humans
   

   That imports everything in the foreign file from a different directory.

Example 5, use os.system("python yourfile.py")

import os
os.system("python yourfile.py")

Example 6, import your file via piggybacking the python startuphook:

Update: This example used to work for both python2 and 3, but now only works for python2. python3 got rid of this user startuphook feature set because it was abused by low-skill python library writers, using it to impolitely inject their code into the global namespace, before all user-defined programs. If you want this to work for python3, you’ll have to get more creative. If I tell you how to do it, python developers will disable that feature set as well, so you’re on your own.

See: https://docs.python.org/2/library/user.html

Put this code into your home directory in ~/.pythonrc.py

class secretclass:
    def secretmessage(cls, myarg):
        return myarg + " is if.. up in the sky, the sky"
    secretmessage = classmethod( secretmessage )

    def skycake(cls):
        return "cookie and sky pie people can't go up and "
    skycake = classmethod( skycake )

Put this code into your main.py (can be anywhere):

import user
msg = "The only way skycake tates good" 
msg = user.secretclass.secretmessage(msg)
msg += user.secretclass.skycake()
print(msg + " have the sky pie! SKYCAKE!")

Run it, you should get this:

$ python main.py
The only way skycake tates good is if.. up in the sky, 
the skycookie and sky pie people can't go up and  have the sky pie! 
SKYCAKE!

If you get an error here: ModuleNotFoundError: No module named 'user' then it means you’re using python3, startuphooks are disabled there by default.

Credit for this jist goes to: https://github.com/docwhat/homedir-examples/blob/master/python-commandline/.pythonrc.py Send along your up-boats.

Example 7, Most Robust: Import files in python with the bare import command:

1. Make a new directory /home/el/foo5/
2. Make a new directory /home/el/foo5/herp

3. Make an empty file named __init__.py under herp:

   el@apollo:/home/el/foo5/herp$ touch __init__.py
   el@apollo:/home/el/foo5/herp$ ls
   __init__.py
   

4. Make a new directory /home/el/foo5/herp/derp

5. Under derp, make another __init__.py file:

   el@apollo:/home/el/foo5/herp/derp$ touch __init__.py
   el@apollo:/home/el/foo5/herp/derp$ ls
   __init__.py
   

6. Under /home/el/foo5/herp/derp make a new file called yolo.py Put this in there:

   def skycake():
     print "SkyCake evolves to stay just beyond the cognitive reach of " +
     "the bulk of men. SKYCAKE!!"
   

7. The moment of truth, Make the new file /home/el/foo5/main.py, put this in there;

   from herp.derp.yolo import skycake
   skycake()
   

8. Run it:

   el@apollo:/home/el/foo5$ python main.py
   SkyCake evolves to stay just beyond the cognitive reach of the bulk 
   of men. SKYCAKE!!
   

   The empty __init__.py file communicates to the python interpreter that the developer intends this directory to be an importable package.

If you want to see my post on how to include ALL .py files under a directory see here: https://stackoverflow.com/a/20753073/445131

To import a specific Python file at ‘runtime’ with a known name:

import os
import sys

…

scriptpath = "../Test/"

# Add the directory containing your module to the Python path (wants absolute paths)
sys.path.append(os.path.abspath(scriptpath))

# Do the import
import MyModule

You do not have many complex methods to import a python file from one folder to another. Just create a __init__.py file to declare this folder is a python package and then go to your host file where you want to import just type

from root.parent.folder.file import variable, class, whatever

Import doc .. — Link for reference

The __init__.py files are required to make Python treat the directories as containing packages, this is done to prevent directories with a common name, such as string, from unintentionally hiding valid modules that occur later on the module search path.

__init__.py can just be an empty file, but it can also execute initialization code for the package or set the __all__ variable.

mydir/spam/__init__.py
mydir/spam/module.py
import spam.module
or
from spam import module

First case: You want to import file A.py in file B.py, these two files are in the same folder, like this:

. 
├── A.py 
└── B.py

You can do this in file B.py:

import A

or

from A import *

or

from A import THINGS_YOU_WANT_TO_IMPORT_IN_A

Then you will be able to use all the functions of file A.py in file B.py

Second case: You want to import file folder/A.py in file B.py, these two files are not in the same folder, like this:

.
├── B.py
└── folder
     └── A.py

You can do this in file B:

import folder.A

or

from folder.A import *

or

from folder.A import THINGS_YOU_WANT_TO_IMPORT_IN_A

Then you will be able to use all the functions of file A.py in file B.py

Summary: In the first case, file A.py is a module that you imports in file B.py, you used the syntax import module_name. In the second case, folder is the package that contains the module A.py, you used the syntax import package_name.module_name.

For more info on packages and modules, consult this link.

from file import function_name  ######## Importing specific function
function_name()                 ######## Calling function

and

import file              ######## Importing whole package
file.function1_name()    ######## Calling function
file.function2_name()    ######## Calling function

Here are the two simple ways I have understood by now and make sure your “file.py” file which you want to import as a library is present in your current directory only.

If the function defined is in a file x.py:

def greet():
    print('Hello! How are you?')

In the file where you are importing the function, write this:

from x import greet

This is useful if you do not wish to import all the functions in a file.

the best way to import .py files is by way of __init__.py. the simplest thing to do, is to create an empty file named __init__.py in the same directory that your.py file is located.

this post by Mike Grouchy is a great explanation of __init__.py and its use for making, importing, and setting up python packages.

How I import is import the file and use shorthand of it’s name.

import DoStuff.py as DS
DS.main()

Don’t forget that your importing file MUST BE named with .py extension

I’d like to add this note I don’t very clearly elsewhere; inside a module/package, when loading from files, the module/package name must be prefixed with the mymodule. Imagine mymodule being layout like this:

/main.py
/mymodule
    /__init__.py
    /somefile.py
    /otherstuff.py

When loading somefile.py/otherstuff.py from __init__.py the contents should look like:

from mymodule.somefile import somefunc
from mymodule.otherstuff import otherfunc

In case the module you want to import is not in a sub-directory, then try the following and run app.py from the deepest common parent directory:

Directory Structure:

/path/to/common_dir/module/file.py
/path/to/common_dir/application/app.py
/path/to/common_dir/application/subpath/config.json

In app.py, append path of client to sys.path:

import os, sys, inspect

sys.path.append(os.getcwd())
from module.file import MyClass
instance = MyClass()

Optional (If you load e.g. configs) (Inspect seems to be the most robust one for my use cases)

# Get dirname from inspect module
filename = inspect.getframeinfo(inspect.currentframe()).filename
dirname = os.path.dirname(os.path.abspath(filename))
MY_CONFIG = os.path.join(dirname, "subpath/config.json")

Run

user@host:/path/to/common_dir$ python3 application/app.py

This solution works for me in cli, as well as PyCharm.

There are couple of ways of including your python script with name abc.py

1. e.g. if your file is called abc.py (import abc) Limitation is that your file should be present in the same location where your calling python script is.

import abc

2. e.g. if your python file is inside the Windows folder. Windows folder is present at the same location where your calling python script is.

from folder import abc

3. Incase abc.py script is available insider internal_folder which is present inside folder

from folder.internal_folder import abc

4. As answered by James above, in case your file is at some fixed location

import os
import sys
scriptpath = “../Test/MyModule.py”
sys.path.append(os.path.abspath(scriptpath))
import MyModule

In case your python script gets updated and you don’t want to upload – use these statements for auto refresh. Bonus :)

%load_ext autoreload 
%autoreload 2

Just to import python file in another python file

lets say I have helper.py python file which has a display function like,

def display():
    print("I'm working sundar gsv")

Now in app.py, you can use the display function,

import helper
helper.display()

The output,

I'm working sundar gsv

NOTE: No need to specify the .py extension.

This may sound crazy but you can just create a symbolic link to the file you want to import if you’re just creating a wrapper script to it.

You can also do this: from filename import something

example: from client import Client Note that you do not need the .py .pyw .pyui extension.

This is how I did to call a function from a python file, that is flexible for me to call any functions.

import os, importlib, sys

def callfunc(myfile, myfunc, *args):
    pathname, filename = os.path.split(myfile)
    sys.path.append(os.path.abspath(pathname))
    modname = os.path.splitext(filename)[0]
    mymod = importlib.import_module(modname)
    result = getattr(mymod, myfunc)(*args)
    return result

result = callfunc("pathto/myfile.py", "myfunc", arg1, arg2)

There are many ways, as listed above, but I find that I just want to import he contents of a file, and don’t want to have to write lines and lines and have to import other modules. So, I came up with a way to get the contents of a file, even with the dot syntax (file.property) as opposed to merging the imported file with yours.
First of all, here is my file which I’ll import, data.py

    testString= "A string literal to import and test with"

Note: You could use the .txt extension instead.
In mainfile.py, start by opening and getting the contents.

    #!usr/bin/env python3
    Data=open('data.txt','r+').read()

Now you have the contents as a string, but trying to access data.testString will cause an error, as data is an instance of the str class, and even if it does have a property testString it will not do what you expected.
Next, create a class. For instance (pun intended), ImportedFile

    class ImportedFile:

And put this into it (with the appropriate indentation):

    exec(data)

And finally, re-assign data like so:

    data=ImportedFile()

And that’s it! Just access like you would for any-other module, typing print(data.testString) will print to the console A string literal to import and test with.
If, however, you want the equivalent of from mod import * just drop the class, instance assignment, and de-dent the exec.

Hope this helps:)
-Benji

One very unknown feature of Python is the ability to import zip files:

library.zip
|-library
|--__init__.py

The file __init__.py of the package contains the following:

def dummy():
    print 'Testing things out...'

We can write another script which can import a package from the zip archive. It is only necessary to add the zip file to the sys.path.

import sys
sys.path.append(r'library.zip')

import library

def run():
    library.dummy()

run()