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[Blog·Tanky Woo](https://blog.tankywoo.com/) / [ABOUT](https://blog.tankywoo.com/about.html) / [TAGS](https://blog.tankywoo.com/tags.html) / [RSS](https://blog.tankywoo.com/feed.xml) # Python Relative and Absolute Import \[ [\#Python](https://blog.tankywoo.com/tags/Python.html) \] \[ October 7, 2013 \] The [PEP 328: Absolute and Relative Imports](http://docs.python.org/2/whatsnew/2.5.html#pep-328-absolute-and-relative-imports) explans very detailed. The `absolute_import` feature is default in `Python 3.x`. (I use `Python 2.7.x`) Use the examples pep328 gives: ``` pkg ├── __init__.py ├── main.py └── string.py ``` The content of string.py ``` #!/usr/bin/env python # -*- coding: utf-8 -*- def say_hello(): print "say hello" ``` The content of first version main.py: ``` #!/usr/bin/env python # -*- coding: utf-8 -*- import string string.say_hello() ``` ``` # move to the parent dir of pkg $ python -m pkg.main say hello ``` This will use the relative string.py module, not the Python’s standard string module. When use `absolute_import`: From pep328: > Once absolute imports are the default, `import string` will always find the standard library’s version. It’s **suggested** that users should begin using absolute imports as much as possible, so it’s preferable to begin writing `from pkg import string` in your code. ``` from __future__ import absolute_import #import string # This is error because `import string` will use the standard string module from pkg import string string.say_hello() ``` > Relative imports are still possible by adding **a leading period** to the module name when using the `from ... import` form: ``` from __future__ import absolute_import from . import string # This is the same as `from pkg import string` string.say_hello() ``` or ``` from __future__ import absolute_import from .string import say_hello say_hello() ``` Use `print(string)` to see which string module to import *** 2015-02-22 Supplement: main.py: ``` #!/usr/bin/env python # -*- coding: utf-8 -*- from __future__ import absolute_import import string print(string) string.say_hello() ``` If run code by: ``` cd pkg $ python pkg/main.py <module 'string' from '/path/to/my/pkg/string.pyc'> say hello ``` It will always use local string.py, because current path is the first in `sys.path` change main.py to: ``` #!/usr/bin/env python # -*- coding: utf-8 -*- from . import string print(string) string.say_hello() ``` run code: ``` cd pkg $ python pkg/main.py Traceback (most recent call last): File "pkg/main.py", line 3, in <module> from . import string ValueError: Attempted relative import in non-package ``` This [answer](http://stackoverflow.com/a/11537218/1276501) is detailed: > To elaborate on @Ignacio’s answer: the python import mechanism works relative to the **name** of the current file. When you execute a file directly, it doesn’t have it’s usual name, but has “**main**” as its name instead. So relative imports don’t work. You can, as Igancio suggested, execute it using the -m option. If you have a part of your package that is mean to be run as a script, you can also use the **package** attribute to tell that file what name it’s supposed to have in the package hierarchy. See <http://www.python.org/dev/peps/pep-0366/> for details. Absolute/Relative import is to package. In Python 2.x(by now is Python 2.7.x), the default import feature is `implicit relative import`. As above see, it will first import the same-named module under package. Use absolute import as default, Python will only import by the `sys.path` sequence. And if you want to use relative import, you must use `explicit relative import` That as list in `import this`: > Explicit is better than implicit *** 2015-08-25 Supplement: 前阵子写了一个功能脚本utils/redis.py, 封装了redis-py(import redis)实现一些功能检查: ``` TankyWoo % tree . ├── main.py └── utils ├── __init__.py └── redis.py 1 directory, 3 files TankyWoo % more main.py #!/usr/bin/env python # -*- coding: utf-8 -*- from utils import redis if __name__ == '__main__': redis.func() TankyWoo % more utils/redis.py #!/usr/bin/env python # -*- coding: utf-8 -*- from __future__ import absolute_import import redis def func(): print redis.Redis if __name__ == '__main__': func() ``` 这块在utils/redis.py里必须指定绝对导入, 否则就相当于导入自身了. Ref: 1. [PEP 0328](https://www.python.org/dev/peps/pep-0328/) 2. [What’s wrong with relative imports in Python?](http://programmers.stackexchange.com/questions/159503/whats-wrong-with-relative-imports-in-python) 3. [Attempted relative import in non-package even with **init**.py](http://stackoverflow.com/questions/11536764/attempted-relative-import-in-non-package-even-with-init-py) 4. [Why does PEP 8 advise against explicit relative imports?](http://www.gossamer-threads.com/lists/python/dev/1072694) 5. [Python导入的路径，绝对导入，相对导入](http://zhuhaipeng.me/blog/2014/08/26/pythondao-ru-de-lu-jing-,jue-dui-dao-ru-,xiang-dui-dao-ru/) 6. [Python 类库引入机制](https://github.com/Liuchang0812/slides/tree/master/pycon2015cn) Copyright © 2013-2021 \| [京ICP备16016622号-2](https://beian.miit.gov.cn/) \| Powered by [Hugo](https://gohugo.io/).