How to do relative imports in Python

Question

Imagine this directory structure   app       init   py    sub1          init   py       mod1 py    sub2          init   py       mod2 py   I m coding mod1  and I need to import something from mod2  How should I do it     I tried from   sub2 import mod2 but I m getting an  Attempted relative import in non-package    I googled around but found only  sys path manipulation  hacks  Isn t there a clean way       Edit  all my   init   py s are currently empty    Edit2  I m trying to do this because sub2 contains classes that are shared across sub packages  sub1  subX  etc     Edit3  The behaviour I m looking for is the same as described in PEP 366  thanks John B

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explanation of nosklo s answer with examples  note  all   init   py files are empty   main py app  - gt        init   py     package a  - gt           init   py        fun a py     package b  - gt           init   py        fun b py   app package a fun a py  def print a        print  This is a function in dir package a    app package b fun b py  from app package a fun a import print a def print b        print  This is a function in dir package b      print  going to call a function in dir package a      print  -  30     print a     main py  from app package b import fun b fun b print b     if you run   python main py it returns   This is a function in dir package b going to call a function in dir package a ------------------------------ This is a function in dir package a    main py does  from app package b import fun b  fun b py does from app package a fun a import print a   so file in folder package b used file in folder package a  which is what you want  Right

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Here is the solution which works for me   I do the relative imports as  from   sub2 import mod2 and then  if I want to run mod1 py then I go to the parent directory of app and run the module using the python -m switch as  python -m app sub1 mod1   The real reason why this problem occurs with relative imports  is that relative imports works by taking the   name   property of the module  If the module is being directly run  then   name   is set to   main   and it doesn t contain any information about package structure  And  thats why python complains about the relative import in non-package error     So  by using the -m switch you provide the package structure information to python  through which it can resolve the relative imports successfully   I have encountered this problem many times while doing relative imports  And  after reading all the previous answers  I was still not able to figure out how to solve it  in a clean way  without needing to put boilerplate code in all files   Though some of the comments were really helpful  thanks to  ncoghlan and  XiongChiamiov   Hope this helps someone who is fighting with relative imports problem  because going through PEP is really not fun

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main py setup py app  - gt        init   py     package a  - gt           init   py        module a py     package b  - gt           init   py        module b py    You run python main py  main py does  import app package a module a module a py does import app package b module b   Alternatively 2 or 3 could use  from app package a import module a  That will work as long as you have app in your PYTHONPATH  main py could be anywhere then   So you write a setup py to copy  install  the whole app package and subpackages to the target system s python folders  and main py to target system s script folders

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This is solved 100     app    main py  settings    local setings py    Import settings local setting py in app main py   main py   import sys sys path insert 0      settings     try      from local settings import   except ImportError      print  No Import

User · Answer

Take a look at http   docs python org whatsnew 2 5 html pep-328-absolute-and-relative-imports  You could do   from  mod1 import stuff

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Here is the solution which works for me   I do the relative imports as  from   sub2 import mod2 and then  if I want to run mod1 py then I go to the parent directory of app and run the module using the python -m switch as  python -m app sub1 mod1   The real reason why this problem occurs with relative imports  is that relative imports works by taking the   name   property of the module  If the module is being directly run  then   name   is set to   main   and it doesn t contain any information about package structure  And  thats why python complains about the relative import in non-package error     So  by using the -m switch you provide the package structure information to python  through which it can resolve the relative imports successfully   I have encountered this problem many times while doing relative imports  And  after reading all the previous answers  I was still not able to figure out how to solve it  in a clean way  without needing to put boilerplate code in all files   Though some of the comments were really helpful  thanks to  ncoghlan and  XiongChiamiov   Hope this helps someone who is fighting with relative imports problem  because going through PEP is really not fun

User · Answer

Take a look at http   docs python org whatsnew 2 5 html pep-328-absolute-and-relative-imports  You could do   from  mod1 import stuff

User · Answer

Everyone seems to want to tell you what you should be doing rather than just answering the question   The problem is that you re running the module as    main    by passing the mod1 py as an argument to the interpreter   From PEP 328      Relative imports use a module s   name   attribute to determine that module s position in the package hierarchy  If the module s name does not contain any package information  e g  it is set to    main     then relative imports are resolved as if the module were a top level module  regardless of where the module is actually located on the file system    In Python 2 6  they re adding the ability to reference modules relative to the main module   PEP 366 describes the change   Update  According to Nick Coghlan  the recommended alternative is to run the module inside the package using the -m switch

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On top of what John B said  it seems like setting the   package   variable should help  instead of changing   main   which could screw up other things  But as far as I could test  it doesn t completely work as it should   I have the same problem and neither PEP 328 or 366 solve the problem completely  as both  by the end of the day  need the head of the package to be included in sys path  as far as I could understand   I should also mention that I did not find how to format the string that should go into those variables  Is it  package head subfolder module name  or what

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explanation of nosklo s answer with examples  note  all   init   py files are empty   main py app  - gt        init   py     package a  - gt           init   py        fun a py     package b  - gt           init   py        fun b py   app package a fun a py  def print a        print  This is a function in dir package a    app package b fun b py  from app package a fun a import print a def print b        print  This is a function in dir package b      print  going to call a function in dir package a      print  -  30     print a     main py  from app package b import fun b fun b print b     if you run   python main py it returns   This is a function in dir package b going to call a function in dir package a ------------------------------ This is a function in dir package a    main py does  from app package b import fun b  fun b py does from app package a fun a import print a   so file in folder package b used file in folder package a  which is what you want  Right

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Let me just put this here for my own reference  I know that it is not good Python code  but I needed a script for a project I was working on and I wanted to put the script in a scripts directory   import os path import sys sys path append os path abspath os path join os path dirname   file

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From Python doc      In Python 2 5  you can switch import   s behaviour to absolute imports using a from   future   import absolute import directive  This absolute- import behaviour will become the default in a future version  probably Python 2 7   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

User · Answer

On top of what John B said  it seems like setting the   package   variable should help  instead of changing   main   which could screw up other things  But as far as I could test  it doesn t completely work as it should   I have the same problem and neither PEP 328 or 366 solve the problem completely  as both  by the end of the day  need the head of the package to be included in sys path  as far as I could understand   I should also mention that I did not find how to format the string that should go into those variables  Is it  package head subfolder module name  or what

User · Answer

Everyone seems to want to tell you what you should be doing rather than just answering the question   The problem is that you re running the module as    main    by passing the mod1 py as an argument to the interpreter   From PEP 328      Relative imports use a module s   name   attribute to determine that module s position in the package hierarchy  If the module s name does not contain any package information  e g  it is set to    main     then relative imports are resolved as if the module were a top level module  regardless of where the module is actually located on the file system    In Python 2 6  they re adding the ability to reference modules relative to the main module   PEP 366 describes the change   Update  According to Nick Coghlan  the recommended alternative is to run the module inside the package using the -m switch

User · Answer

As  EvgeniSergeev says in the comments to the OP  you can import code from a  py file at an arbitrary location with   import imp  foo   imp load source  module name     path to file py   foo MyClass     This is taken from this SO answer

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I found it s more easy to set  PYTHONPATH  enviroment variable to the top folder   bash  export PYTHONPATH  PATH TO APP   then   import sub1 func1     more import   of course  PYTHONPATH is  global   but it didn t raise trouble for me yet

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main py setup py app  - gt        init   py     package a  - gt           init   py        module a py     package b  - gt           init   py        module b py    You run python main py  main py does  import app package a module a module a py does import app package b module b   Alternatively 2 or 3 could use  from app package a import module a  That will work as long as you have app in your PYTHONPATH  main py could be anywhere then   So you write a setup py to copy  install  the whole app package and subpackages to the target system s python folders  and main py to target system s script folders

User · Answer

Everyone seems to want to tell you what you should be doing rather than just answering the question   The problem is that you re running the module as    main    by passing the mod1 py as an argument to the interpreter   From PEP 328      Relative imports use a module s   name   attribute to determine that module s position in the package hierarchy  If the module s name does not contain any package information  e g  it is set to    main     then relative imports are resolved as if the module were a top level module  regardless of where the module is actually located on the file system    In Python 2 6  they re adding the ability to reference modules relative to the main module   PEP 366 describes the change   Update  According to Nick Coghlan  the recommended alternative is to run the module inside the package using the -m switch

User · Answer

You have to append the module   s path to PYTHONPATH    export PYTHONPATH    PYTHONPATH   path to your module

User · Answer

Everyone seems to want to tell you what you should be doing rather than just answering the question   The problem is that you re running the module as    main    by passing the mod1 py as an argument to the interpreter   From PEP 328      Relative imports use a module s   name   attribute to determine that module s position in the package hierarchy  If the module s name does not contain any package information  e g  it is set to    main     then relative imports are resolved as if the module were a top level module  regardless of where the module is actually located on the file system    In Python 2 6  they re adding the ability to reference modules relative to the main module   PEP 366 describes the change   Update  According to Nick Coghlan  the recommended alternative is to run the module inside the package using the -m switch

User · Answer

main py setup py app  - gt        init   py     package a  - gt           init   py        module a py     package b  - gt           init   py        module b py    You run python main py  main py does  import app package a module a module a py does import app package b module b   Alternatively 2 or 3 could use  from app package a import module a  That will work as long as you have app in your PYTHONPATH  main py could be anywhere then   So you write a setup py to copy  install  the whole app package and subpackages to the target system s python folders  and main py to target system s script folders

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def import path fullpath                Import a file with full path specification  Allows one to     import from anywhere  something   import   does not do               path  filename   os path split fullpath      filename  ext   os path splitext filename      sys path append path      module     import   filename      reload module    Might be out of date     del sys path -1      return module   I m using this snippet to import modules from paths  hope that helps

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This is unfortunately a sys path hack  but it works quite well   I encountered this problem with another layer  I already had a module of the specified name  but it was the wrong module   what I wanted to do was the following  the module I was working from was module3    mymodule       init   py    mymodule1          init   py       mymodule1 1    mymodule2          init   py       mymodule2 1   import mymodule mymodule1 mymodule1 1     Note that I have already installed mymodule  but in my installation I do not have  mymodule1   and I would get an ImportError because it was trying to import from my installed modules   I tried to do a sys path append  and that didn t work   What did work was a sys path insert  if   name         main         sys path insert 0             So kind of a hack  but got it all to work  So keep in mind  if you want your decision to override other paths then you need to use sys path insert 0  pathname  to get it to work   This was a very frustrating sticking point for me  allot of people say to use the  append  function to sys path  but that doesn t work if you already have a module defined  I find it very strange behavior

User · Answer

main py setup py app  - gt        init   py     package a  - gt           init   py        module a py     package b  - gt           init   py        module b py    You run python main py  main py does  import app package a module a module a py does import app package b module b   Alternatively 2 or 3 could use  from app package a import module a  That will work as long as you have app in your PYTHONPATH  main py could be anywhere then   So you write a setup py to copy  install  the whole app package and subpackages to the target system s python folders  and main py to target system s script folders

User · Answer

This is unfortunately a sys path hack  but it works quite well   I encountered this problem with another layer  I already had a module of the specified name  but it was the wrong module   what I wanted to do was the following  the module I was working from was module3    mymodule       init   py    mymodule1          init   py       mymodule1 1    mymodule2          init   py       mymodule2 1   import mymodule mymodule1 mymodule1 1     Note that I have already installed mymodule  but in my installation I do not have  mymodule1   and I would get an ImportError because it was trying to import from my installed modules   I tried to do a sys path append  and that didn t work   What did work was a sys path insert  if   name         main         sys path insert 0             So kind of a hack  but got it all to work  So keep in mind  if you want your decision to override other paths then you need to use sys path insert 0  pathname  to get it to work   This was a very frustrating sticking point for me  allot of people say to use the  append  function to sys path  but that doesn t work if you already have a module defined  I find it very strange behavior

User · Answer

Guido views running scripts within a package as an anti-pattern   rejected PEP-3122   I have spent so much time trying to find a solution  reading related posts here on Stack Overflow and saying to myself  there must be a better way    Looks like there is not

User · Answer

As  EvgeniSergeev says in the comments to the OP  you can import code from a  py file at an arbitrary location with   import imp  foo   imp load source  module name     path to file py   foo MyClass     This is taken from this SO answer

User · Answer

def import path fullpath                Import a file with full path specification  Allows one to     import from anywhere  something   import   does not do               path  filename   os path split fullpath      filename  ext   os path splitext filename      sys path append path      module     import   filename      reload module    Might be out of date     del sys path -1      return module   I m using this snippet to import modules from paths  hope that helps

User · Answer

This is solved 100     app    main py  settings    local setings py    Import settings local setting py in app main py   main py   import sys sys path insert 0      settings     try      from local settings import   except ImportError      print  No Import

User · Answer

I found it s more easy to set  PYTHONPATH  enviroment variable to the top folder   bash  export PYTHONPATH  PATH TO APP   then   import sub1 func1     more import   of course  PYTHONPATH is  global   but it didn t raise trouble for me yet

User · Answer

You have to append the module   s path to PYTHONPATH    export PYTHONPATH    PYTHONPATH   path to your module

User · Answer

Guido views running scripts within a package as an anti-pattern   rejected PEP-3122   I have spent so much time trying to find a solution  reading related posts here on Stack Overflow and saying to myself  there must be a better way    Looks like there is not

User · Answer

From Python doc      In Python 2 5  you can switch import   s behaviour to absolute imports using a from   future   import absolute import directive  This absolute- import behaviour will become the default in a future version  probably Python 2 7   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

User · Answer

Let me just put this here for my own reference  I know that it is not good Python code  but I needed a script for a project I was working on and I wanted to put the script in a scripts directory   import os path import sys sys path append os path abspath os path join os path dirname   file

[python] How to do relative imports in Python?

app/package_a/fun_a.py

app/package_b/fun_b.py

main.py

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