I have a module that conflicts with a built-in module. For example, a myapp.email module defined in myapp/email.py.
I can reference myapp.email anywhere in my code without issue. However, I need to reference the built-in email module from my email module.
# myapp/email.py
from email import message_from_string
It only finds itself, and therefore raises an ImportError, since myapp.email doesn't have a message_from_string method. import email causes the same issue when I try email.message_from_string.
Is there any native support to do this in Python, or am I stuck with renaming my "email" module to something more specific?
You will want to read about Absolute and Relative Imports which addresses this very problem. Use:
from __future__ import absolute_import
Using that, any unadorned package name will always refer to the top level package. You will then need to use relative imports (from .email import ...) to access your own package.
NOTE: The above from ... line needs to be put into any 2.x Python .py files above the import ... lines you're using. In Python 3.x this is the default behavior and so is no longer needed.
Related
For some reason, I had to change a module name from A.py to 0880ceae-8a46-11eb-bcf6-38f9d349be8e.py. 0880ceae-8a46-11eb-bcf6-38f9d349be8e.py is a uid generated by uuid.uuid1().
After my change, I try to import a class B from the py file by the following two ways, both do not work out.
First solution is to import directly
from 0880ceae-8a46-11eb-bcf6-38f9d349be8e import B
It has an error SyntaxError: invalid token
Second solution is to define a variable before import
uid = '0880ceae-8a46-11eb-bcf6-38f9d349be8e'
from uid import Model_API
And it has en error ModuleNotFoundError: No module named 'uid'
Anyone has a good idea? Thanks.
Here is possible solution to your problem tested using python3:
# Modern approach
import importlib
module = importlib.import_module(".", "0880ceae-8a46-11eb-bcf6-38f9d349be8e")
module.hello()
# Deprecated way
module = __import__("0880ceae-8a46-11eb-bcf6-38f9d349be8e")
module.hello()
Both of the above methods are tested and works.
Here are the rules to keep in mind:
Check your filename should end with .py extension, .py.py will cause ModuleNotFoundError.
Make sure to not include .py extension while using in importlib module.
Could anyone please explains what from .object import object means?
I know that everything extends object just like in Java.But what does .object means?
I saw this piece of code in the source code in psycopg2:
from .object import object
class cursor(object):
pass
That's the new syntax for explicit relative imports. It means import from the current package.
Without the ., if you had a file _object.py for some indecipherable reason next to your main script, object would break. With the ., it ensures it gets its own module.
The thing that defines what a "current package" is that it should say from where the importing package is. It basically means the current namespace or package directory.
Hope this helps!
From the docs:
One leading dot means the current package where the module making the import exists. Two dots means up one package level. Three dots is up two levels, etc. So if you execute from . import mod from a module in the pkg package then you will end up importing pkg.mod. If you execute from ..subpkg2 import mod from within pkg.subpkg1 you will import pkg.subpkg2.mod. The specification for relative imports is contained within PEP 328.
The dot is basically telling the program to search in the current directory before looking at the files in your python path. If object exists in both the current directory and your python path, only the one from the former will be imported.
so I'm new to Python and Flask and I'm currently playing around with some CRUD-statements within Flask/Python
I want to know if I fully understand what's going on but I'm a little bit unsecure regarding the following topic: Modules, Packages import
I want to connect to my SQLite database with Flask. Doing so, I have to do some imports:
import os
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
First thing after the imports are done is to set a basedirectory (=basedir):
basedir = os.path.abspath(os.path.dirname(__file__))
And regarding those steps I have some questions:
Question:
import os
from flask import Flask
Does the first import ("import os") mean that I'm only using a Module called "os"? It's a standalone .py - "file" including a class, some attributes and methods, right?
Does the second import ("from flask import Flask") mean that I'm using the package "flask" and import the module "Flask"? If, e.g., there would be another import like "render_template", does that mean I'm using this module or is it a method from the module "Flask"?
Second question:
basedir = os.path.abspath(os.path.dirname(__file__))
I'd like to understand this code. First of all, I'm declaring a variable called basedir. Then I am going to set the value of that variable to the absolute path for the current .py-script. Now to the single steps:
os => means that I'm using the already imported module "os", right?
path => means that I'm using an attribute from that module?
abspath => means that I'm using a method within the "os" module called "abspath(value)"?
The next thing would be clear if I get an answer to the other things: "
(os.path.dirname(__filename__))
__filename__ => that's a built-in Python attribute, right?
Does the first import ("import os") mean that I'm only using a Module called "os"?
As the statement implies, you're importing the OS module, so you can use the functions in the os module in your python script.
So, now you can make os.function() statements in your script. The OS module is installed with Python by default. Here is info on the os module.
Does the second import ("from flask import Flask") mean that I'm using the package "flask" and import the module "Flask"? If, e.g., there would be another import like "render_template", does that mean I'm using this module or is it a method from the module "Flask"?
This can be confusing since the function name and the import statement have the same name. You're only importing the function flask from the module Flask, not all the functions present in the Flask module.
This can be done for multiple reasons. On is to simplify calling the function. Another could be to save system resources, since you're only
os => means that I'm using the already imported module "os", right? path => means that I'm using an attribute from that module? abspath => means that I'm using a method within the "os" module called "abspath(value)"?
Exactly, read the docs for an explanation by the developers of the module.
Filename
Here is an explanation of the filename usage in Python.
Im gonna answer the first question. Basically when you do just an import, python imports the entire file with all of its modules and functions. Like when you import math you can use math.ceil and other functions. However when you say from math import add you only get a specific module which is ceil like ceil(2.7).
For further details read up here
So my first python program, I downloaded the macholib package from PYPI, then unzipped it and ran installed the setup.py using python install, now I'm trying to run a program where I first import the macholib, then when I try to access methods like Macho, it gives me an error saying macholib module has no attributes called Macho.
My understanding is macholib is a package and not a module or something, hence I cant use the contents of the package.
Please answer, I've wasted too much time on such a simple newbie issue.
running a mac with the latest version of python.
Code:
import sys
import macholib
MachO(DivXInstaller.dmg)
I tried macholib.MachO(DivXInstaller.dmg) and macholib.MachO.MachO(DivXInstaller.dmg)
Error for python test.py
Traceback (most recent call last):
File "test.py", line 3, in <module>
MachO(DivXInstaller.dmg)
NameError: name 'MachO' is not defined
You have this line in your code:
MachO(DivXInstaller.dmg)
However, the name MachO is not defined anywhere. So Python tells you this with the error
NameError: name 'MachO' is not defined
If you want to use the MachO module under the name MachO, you have to import it:
from macholib import MachO
This you have not done, which is the cause of your error. All you did was
import macholib
which gives you the name "macholib" that you can use. However, macholib contains mostly submodules which you can not access like that, so that is not particularly useful. If you don't want to pollute the namespace, you can import MachO as
import machlibo.MachO
Which gives you access to the MachO module as macholib.MachO
You haven't defined DivXInstaller.dmg either, so that's going to be your next error. I recommend that you go through a Python tutorial before you start programming in it.
An import statement defines a namespace. Hence, in order to use something defined in the module or package, you need to qualify it. In this case, the module itself is macholib.MachO but you need to dig deeper, to the actual class MachO which, slightly confusingly, has the same name, so you need to import macholib.MachO and use macholib.MachO.MachO (note that when I try to do this I get an error "DistributionNotFound: altgraph", however).
Note further that it takes a filename as an argument, which is a string. Moreover, you are actually creating an instance of a class, so you probably mean
mlib = macholib.MachO.MachO("DivXInstaller.dmg")
where now mlib is actually the object you need to manipulate with further calls...
Alternately you can do from macholib import MachO or even from macholib.MachO import MachO so you could use MachO.MachO(...) or MachO(...) directly.
This is so simple if you understand Python Packages vs. Modules and import vs. from import:
A Python module is simply a Python source file.
A Python package is simply a directory of Python module(s).
1- import:
import package1.package2.module1
To access module1 classes, functions or variables you should use the whole namespace: package1.package2.modlue1.class1
You cannot import a class or function this way: (wrong)
import package1.package2.class1
2- from ... import
Instead use "from" to import a single class, function or variable of a module:
from package1.package2.module1 import class1
no need to address the whole namespace: class1.method1() works now
Note that you cannot import a method of a class this way
Example:
datetime is a class of module datetime that has a method called utcnow(), to access utcnow() one could:
import datetime
datetime.datetime.utcnow()
Or
from datetime import datetime
datetime.utcnow()
I'm using python and virtualenv/pip. I have a module installed via pip called test_utils (it's django-test-utils). Inside one of my django apps, I want to import that module. However I also have another file test_utils.py in the same directory. If I go import test_utils, then it will import this local file.
Is it possible to make python use a non-local / non-relative / global import? I suppose I can just rename my test_utils.py, but I'm curious.
You can switch the search order by changing sys.path:
del sys.path[0]
sys.path.append('')
This puts the current directory after the system search path, so local files won't shadow standard modules.
My problem was even more elaborate:
importing a global/site-packages module from a file with the same name
Working on aero the pm recycler I wanted access to the pip api, in particular pip.commands.search.SearchCommand from my adapter class Pip in source file pip.py.
In this case trying to modify sys.path is useless, I even went as far as wiping sys.path completely and adding the folder .../site-packages/pip...egg/ as the only item in sys.path and no luck.
I would still get:
print pip.__package__
# 'aero.adapters'
I found two options that did eventually work for me, they should work equally well for you:
using __builtin__.__import__() the built-in function
global_pip = __import__('pip.commands.search', {}, {}, ['SearchCommand'], -1)
SearchCommand = global_pip.SearchCommand
Reading the documentation though, suggests using the following method instead.
using importlib.import_module() the __import__ conv wrapper.
The documentation explains that import_module() is a minor subset of functionality from Python 3.1 to help ease transitioning from 2.7 to 3.1
from importlib import import_module
SearchCommand = import_module('pip.commands.search').SearchCommand
Both options get the job done while import_module() definitely feels more Pythonic if you ask me, would you agree?
nJoy!
I was able to force python to import the global one with
from __future__ import absolute_import
at the beginning of the file (this is the default in python 3.0)
You could reset your sys.path:
import sys
first = sys.path[0]
sys.path = sys.path[1:]
import test_utils
sys.path = first + sys.path
The first entry of sys.path is "always" (as in "per default": See python docs) the current directory, so if you remove it you will do a global import.
Since my test_utils was in a django project, I was able to go from ..test_utils import ... to import the global one.
Though, in first place, I would always consider keeping the name of local file not matching with any global module name, an easy workaround, without modifying 'sys.path' can be to include global module in some other file and then import this global module from that file.
Remember, this file must be in some other folder then in the folder where file with name matching with global module is.
For example.
./project/root/workarounds/global_imports.py
import test_utils as tutil
and then in
./project/root/mycode/test_utils.py
from project.root.workarounds.global_imports import tutil
# tutil is global test_utils
# you can also do
from project.root.workarounds.global_imports import test_utils