Can't get Python to import from a different folder
Question:
I can’t seem to get Python to import a module in a subfolder. I get the error when I try to create an instance of the class from the imported module, but the import itself succeeds. Here is my directory structure:
Server
-server.py
-Models
--user.py
Here’s the contents of server.py:
from sys import path
from os import getcwd
path.append(getcwd() + "\models") #Yes, i'm on windows
print path
import user
u=user.User() #error on this line
And user.py:
class User(Entity):
using_options(tablename='users')
username = Field(String(15))
password = Field(String(64))
email = Field(String(50))
status = Field(Integer)
created = Field(DateTime)
The error is:
AttributeError: ‘module’ object has no attribute ‘User’
Answers:
I believe you need to create a file called __init__.py in the Models directory so that python treats it as a module.
Then you can do:
from Models.user import User
You can include code in the __init__.py (for instance initialization code that a few different classes need) or leave it blank. But it must be there.
You’re missing __init__.py. From the Python tutorial:
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. In the simplest case,
__init__.py can just be an empty file, but it can also execute initialization
code for the package or set the
__all__ variable, described later.
Put an empty file named __init__.py in your Models directory, and all should be golden.
import user
u=user.User() #error on this line
Because of the lack of __init__ mentioned above, you would expect an ImportError which would make the problem clearer.
You don’t get one because ‘user’ is also an existing module in the standard library. Your import statement grabs that one and tries to find the User class inside it; that doesn’t exist and only then do you get the error.
It is generally a good idea to make your import absolute:
import Server.Models.user
to avoid this kind of ambiguity. Indeed from Python 2.7 ‘import user’ won’t look relative to the current module at all.
If you really want relative imports, you can have them explicitly in Python 2.5 and up using the somewhat ugly syntax:
from .user import User
The right way to import a module located on a parent folder, when you don’t have a standard package structure, is:
import os, sys
CURRENT_DIR = os.path.dirname(os.path.abspath(__file__))
sys.path.append(os.path.dirname(CURRENT_DIR))
(you can merge the last two lines but this way is easier to understand).
This solution is cross-platform and is general enough to need not modify in other circumstances.
how do you write out the parameters os.path.dirname…. command?
import os, sys
CURRENT_DIR = os.path.dirname(os.path.abspath(__file__))
sys.path.append(os.path.dirname(CURRENT_DIR))
My preferred way is to have __init__.py on every directory that contains modules that get used by other modules, and in the entry point, override sys.path as below:
def get_path(ss):
return os.path.join(os.path.dirname(__file__), ss)
sys.path += [
get_path('Server'),
get_path('Models')
]
This makes the files in specified directories visible for import, and I can import user from Server.py.
After going through the answers given by these contributors above – Zorglub29, Tom, Mark, Aaron McMillin, lucasamaral, JoeyZhao, Kjeld Flarup, Procyclinsur, martin.zaenker, tooty44 and debugging the issue that I was facing I found out a different use case due to which I was facing this issue.
Hence adding my observations below for anybody’s reference.
In my code I had a cyclic import of classes. For example:
src
|-- utilities.py (has Utilities class that uses Event class)
|-- consume_utilities.py (has Event class that uses Utilities class)
|-- tests
|-- test_consume_utilities.py (executes test cases that involves Event class)
I got following error when I tried to execute python -m pytest tests/test_utilities.py for executing UTs written in test_utilities.py.
ImportError while importing test module '/Users/.../src/tests/test_utilities.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
tests/test_utilities.py:1: in <module>
from utilities import Utilities
...
...
E ImportError: cannot import name 'Utilities'
The way I resolved the error was by re-factoring my code to move the functionality in cyclic import class so that I could remove the cyclic import of classes.
Note, I have __init__.py file in my ‘src‘ folder as well as ‘tests‘ folder and still was able to get rid of the ‘ImportError‘ just by re-factoring the code.
Following stackoverflow link provides much more details on Circular dependency in Python.
I can’t seem to get Python to import a module in a subfolder. I get the error when I try to create an instance of the class from the imported module, but the import itself succeeds. Here is my directory structure:
Server
-server.py
-Models
--user.py
Here’s the contents of server.py:
from sys import path
from os import getcwd
path.append(getcwd() + "\models") #Yes, i'm on windows
print path
import user
u=user.User() #error on this line
And user.py:
class User(Entity):
using_options(tablename='users')
username = Field(String(15))
password = Field(String(64))
email = Field(String(50))
status = Field(Integer)
created = Field(DateTime)
The error is:
AttributeError: ‘module’ object has no attribute ‘User’
I believe you need to create a file called __init__.py in the Models directory so that python treats it as a module.
Then you can do:
from Models.user import User
You can include code in the __init__.py (for instance initialization code that a few different classes need) or leave it blank. But it must be there.
You’re missing __init__.py. From the Python tutorial:
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. In the simplest case,
__init__.py can just be an empty file, but it can also execute initialization
code for the package or set the
__all__ variable, described later.
Put an empty file named __init__.py in your Models directory, and all should be golden.
import user
u=user.User() #error on this line
Because of the lack of __init__ mentioned above, you would expect an ImportError which would make the problem clearer.
You don’t get one because ‘user’ is also an existing module in the standard library. Your import statement grabs that one and tries to find the User class inside it; that doesn’t exist and only then do you get the error.
It is generally a good idea to make your import absolute:
import Server.Models.user
to avoid this kind of ambiguity. Indeed from Python 2.7 ‘import user’ won’t look relative to the current module at all.
If you really want relative imports, you can have them explicitly in Python 2.5 and up using the somewhat ugly syntax:
from .user import User
The right way to import a module located on a parent folder, when you don’t have a standard package structure, is:
import os, sys
CURRENT_DIR = os.path.dirname(os.path.abspath(__file__))
sys.path.append(os.path.dirname(CURRENT_DIR))
(you can merge the last two lines but this way is easier to understand).
This solution is cross-platform and is general enough to need not modify in other circumstances.
how do you write out the parameters os.path.dirname…. command?
import os, sys
CURRENT_DIR = os.path.dirname(os.path.abspath(__file__))
sys.path.append(os.path.dirname(CURRENT_DIR))
My preferred way is to have __init__.py on every directory that contains modules that get used by other modules, and in the entry point, override sys.path as below:
def get_path(ss):
return os.path.join(os.path.dirname(__file__), ss)
sys.path += [
get_path('Server'),
get_path('Models')
]
This makes the files in specified directories visible for import, and I can import user from Server.py.
After going through the answers given by these contributors above – Zorglub29, Tom, Mark, Aaron McMillin, lucasamaral, JoeyZhao, Kjeld Flarup, Procyclinsur, martin.zaenker, tooty44 and debugging the issue that I was facing I found out a different use case due to which I was facing this issue.
Hence adding my observations below for anybody’s reference.
In my code I had a cyclic import of classes. For example:
src
|-- utilities.py (has Utilities class that uses Event class)
|-- consume_utilities.py (has Event class that uses Utilities class)
|-- tests
|-- test_consume_utilities.py (executes test cases that involves Event class)
I got following error when I tried to execute python -m pytest tests/test_utilities.py for executing UTs written in test_utilities.py.
ImportError while importing test module '/Users/.../src/tests/test_utilities.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
tests/test_utilities.py:1: in <module>
from utilities import Utilities
...
...
E ImportError: cannot import name 'Utilities'
The way I resolved the error was by re-factoring my code to move the functionality in cyclic import class so that I could remove the cyclic import of classes.
Note, I have __init__.py file in my ‘src‘ folder as well as ‘tests‘ folder and still was able to get rid of the ‘ImportError‘ just by re-factoring the code.
Following stackoverflow link provides much more details on Circular dependency in Python.