Standard library packages still importable despite modifying sys.path - python

Suppose I want to make packages from standard library non-importable. So "datetime", "collections", and the like should not be importable when running import datetime.
I don't have a use case for this, but achieving this will help me understand how Python is resolving packages.
I have tried doing this:
import sys
sys.path = []
sys.prefix = ''
sys.exec_prefix = ''
But despite this, when I run import datetime, the package is found (which resides in /usr/lib/python3.6 directory on Ubuntu).
I also tried starting Python with python3.6 -S -s to avoid automatic loading of site.py, but also this did not help.
My guess is that the Ubuntu-shipped Python interpreter has the path /usr/lib/pythonX.Y hard-coded, but I was not able to confirm this through extensive internet searching.
So how does Python know that it should look in /usr/lib/pythonX.Y/ directory?

Related

Local vs Global imports python

I am not seeing an answer to this out there, so apologies if this is a duplicate. Basically, I am trying to understand how to force my interpreter (2.7) to import a module from site packages if there is a conflict. For example imagine you are running python from a directory (top_level) that has the following structure:
top_level
----cool_mod
----init.py
----sweet_module.py
but you have already installed sweet module to site packages. When in this directory (but no others) if you run:
from cool_mod.sweet_module import *
you will import from the local module, not the global one. Can I change this somehow?
This situation might arise from the case:
top_level
setup.py
----cool_mod
----init.py
----sweet_module.py
You can run cool_mod.sweet_module before installing if you working directory is top_level. But after installing you can import cool_mod.sweet_module from anywhere. However, if you ever import from this directory, even after installation, you still import the local copy
Inserting the site package directory at the begining of sys.path, and then import.
Or, use imp.load_source to load a module from specified path.

Where is _functools.py located? [duplicate]

How do I learn where the source file for a given Python module is installed? Is the method different on Windows than on Linux?
I'm trying to look for the source of the datetime module in particular, but I'm interested in a more general answer as well.
For a pure python module you can find the source by looking at themodule.__file__.
The datetime module, however, is written in C, and therefore datetime.__file__ points to a .so file (there is no datetime.__file__ on Windows), and therefore, you can't see the source.
If you download a python source tarball and extract it, the modules' code can be found in the Modules subdirectory.
For example, if you want to find the datetime code for python 2.6, you can look at
Python-2.6/Modules/datetimemodule.c
You can also find the latest version of this file on github on the web at
https://github.com/python/cpython/blob/main/Modules/_datetimemodule.c
Running python -v from the command line should tell you what is being imported and from where. This works for me on Windows and Mac OS X.
C:\>python -v
# installing zipimport hook
import zipimport # builtin
# installed zipimport hook
# C:\Python24\lib\site.pyc has bad mtime
import site # from C:\Python24\lib\site.py
# wrote C:\Python24\lib\site.pyc
# C:\Python24\lib\os.pyc has bad mtime
import os # from C:\Python24\lib\os.py
# wrote C:\Python24\lib\os.pyc
import nt # builtin
# C:\Python24\lib\ntpath.pyc has bad mtime
...
I'm not sure what those bad mtime's are on my install!
I realize this answer is 4 years late, but the existing answers are misleading people.
The right way to do this is never __file__, or trying to walk through sys.path and search for yourself, etc. (unless you need to be backward compatible beyond 2.1).
It's the inspect module—in particular, getfile or getsourcefile.
Unless you want to learn and implement the rules (which are documented, but painful, for CPython 2.x, and not documented at all for other implementations, or 3.x) for mapping .pyc to .py files; dealing with .zip archives, eggs, and module packages; trying different ways to get the path to .so/.pyd files that don't support __file__; figuring out what Jython/IronPython/PyPy do; etc. In which case, go for it.
Meanwhile, every Python version's source from 2.0+ is available online at http://hg.python.org/cpython/file/X.Y/ (e.g., 2.7 or 3.3). So, once you discover that inspect.getfile(datetime) is a .so or .pyd file like /usr/local/lib/python2.7/lib-dynload/datetime.so, you can look it up inside the Modules directory. Strictly speaking, there's no way to be sure of which file defines which module, but nearly all of them are either foo.c or foomodule.c, so it shouldn't be hard to guess that datetimemodule.c is what you want.
If you're using pip to install your modules, just pip show $module the location is returned.
The sys.path list contains the list of directories which will be searched for modules at runtime:
python -v
>>> import sys
>>> sys.path
['', '/usr/local/lib/python25.zip', '/usr/local/lib/python2.5', ... ]
from the standard library try imp.find_module
>>> import imp
>>> imp.find_module('fontTools')
(None, 'C:\\Python27\\lib\\site-packages\\FontTools\\fontTools', ('', '', 5))
>>> imp.find_module('datetime')
(None, 'datetime', ('', '', 6))
datetime is a builtin module, so there is no (Python) source file.
For modules coming from .py (or .pyc) files, you can use mymodule.__file__, e.g.
> import random
> random.__file__
'C:\\Python25\\lib\\random.pyc'
Here's a one-liner to get the filename for a module, suitable for shell aliasing:
echo 'import sys; t=__import__(sys.argv[1],fromlist=[\".\"]); print(t.__file__)' | python -
Set up as an alias:
alias getpmpath="echo 'import sys; t=__import__(sys.argv[1],fromlist=[\".\"]); print(t.__file__)' | python - "
To use:
$ getpmpath twisted
/usr/lib64/python2.6/site-packages/twisted/__init__.pyc
$ getpmpath twisted.web
/usr/lib64/python2.6/site-packages/twisted/web/__init__.pyc
In the python interpreter you could import the particular module and then type help(module). This gives details such as Name, File, Module Docs, Description et al.
Ex:
import os
help(os)
Help on module os:
NAME
os - OS routines for Mac, NT, or Posix depending on what system we're on.
FILE
/usr/lib/python2.6/os.py
MODULE DOCS
http://docs.python.org/library/os
DESCRIPTION
This exports:
- all functions from posix, nt, os2, or ce, e.g. unlink, stat, etc.
- os.path is one of the modules posixpath, or ntpath
- os.name is 'posix', 'nt', 'os2', 'ce' or 'riscos'
et al
On windows you can find the location of the python module as shown below:i.e find rest_framework module
New in Python 3.2, you can now use e.g. code_info() from the dis module:
http://docs.python.org/dev/whatsnew/3.2.html#dis
Check out this nifty "cdp" command to cd to the directory containing the source for the indicated Python module:
cdp () {
cd "$(python -c "import os.path as _, ${1}; \
print _.dirname(_.realpath(${1}.__file__[:-1]))"
)"
}
Just updating the answer in case anyone needs it now, I'm at Python 3.9 and using Pip to manage packages. Just use pip show, e.g.:
pip show numpy
It will give you all the details with the location of where pip is storing all your other packages.
On Ubuntu 12.04, for example numpy package for python2, can be found at:
/usr/lib/python2.7/dist-packages/numpy
Of course, this is not generic answer
Another way to check if you have multiple python versions installed, from the terminal.
$ python3 -m pip show pyperclip
Location: /Library/Frameworks/Python.framework/Versions/3.7/lib/python3.7/site-
$ python -m pip show pyperclip
Location: /Users/umeshvuyyuru/Library/Python/2.7/lib/python/site-packages
Not all python modules are written in python. Datetime happens to be one of them that is not, and (on linux) is datetime.so.
You would have to download the source code to the python standard library to get at it.
For those who prefer a GUI solution: if you're using a gui such as Spyder (part of the Anaconda installation) you can just right-click the module name (such as "csv" in "import csv") and select "go to definition" - this will open the file, but also on the top you can see the exact file location ("C:....csv.py")
If you are not using interpreter then you can run the code below:
import site
print (site.getsitepackages())
Output:
['C:\\Users\\<your username>\\AppData\\Local\\Programs\\Python\\Python37', 'C:\\Users\\<your username>\\AppData\\Local\\Programs\\Python\\Python37\\lib\\site-packages']
The second element in Array will be your package location. In this case:
C:\Users\<your username>\AppData\Local\Programs\Python\Python37\lib\site-packages
In an IDE like Spyder, import the module and then run the module individually.
enter image description here
as written above
in python just use help(module)
ie
import fractions
help(fractions)
if your module, in the example fractions, is installed then it will tell you location and info about it, if its not installed it says module not available
if its not available it doesn't come by default with python in which case you can check where you found it for download info

YouCompleteMe/Python can complete for built-in libs, but not site-packages

I just installed ycm, everything looks good, but I found small problem. The problem is as following:
import os # os is built-in library
os. # ycm helps to complete members of the class.
import numpy # numpy is not built-in library, where its location is site-packages.
numpy. # nothing happened. ycm shows 'pattern not found' message.
I think, this would be a simple problem. But I could not find the solution yet. I think, there is some configuration file in which I can define 'search path' for my project.
It would be grateful if I can find a way to solve it.
Best,
Je-Hoon Song
I had the same issue with module 'mpmath' and fixed it in the following manner:
First I retrieved the path where the module was located:
%python3
>>>import mpmath
>>>print(mpmath.__file__)
/usr/lib/python3.4/site-packages/mpmath/__init__.py
Here I found the path of all my "installed" python3 packages to be:
/usr/lib/python3.4/site-packages/
I then simply added to my PYTHONPATH environment variable this path:
%export PYTHONPATH=/usr/lib/python3.4/site-packages/
Then when I used vim sample.py typing import mpmath and following it up with mpmath. YCM showed me all the autocompletions for the mpmath module.
Hope this helps.
I use anaconda python to be my python interpreter in ycm to solve this.
First I modified my vimrc according to full pythong setting in vim.
Then I change g:ycm_python_interpreter_path by
let g:ycm_python_interpreter_path = '/usr/local/anaconda3/bin/python3.8'
In this way I didn't change the system environment variables.
Addtional Info 1:
I think the main problem is that,
my Python interpreter for YCM is my system python (/usr/local/opt/python#3.9/bin/python3.9 ),
which only has limited locally built libraries.
So using the libraries comes with anaconda (/usr/local/anaconda3/bin/python3.8 ) can solve.
Additional Info 2:
By reading :YcmDebugInfo, the main different after edited g:ycm_python_interpreter_path is that:
-- Python completer debug information:
-- Python interpreter: /usr/local/opt/python#3.9/bin/python3.9
-- Python path: ['/usr/local/Cellar/python#3.9/3.9.6/Frameworks/Python.framework/Versions/3.9/lib/python39.zip', '/usr/local/Cellar/python#3.9/3.9.6/Frameworks/Python.framework/Versions/3.9/lib/python3.9', '/usr/local/Cellar/python#3.9/3.9.6/Frameworks/Python.framework/Versions/3.9/lib/python3.9/lib-dynload', '/usr/local/lib/python3.9/site-packages']
-- Python version: 3.9.6
change to
-- Python completer debug information:
-- Python interpreter: /usr/local/anaconda3/bin/python3.8
-- Python path: ['/usr/local/anaconda3/lib/python38.zip', '/usr/local/anaconda3/lib/python3.8', '/usr/local/anaconda3/lib/python3.8/lib-dynload', '/usr/local/anaconda3/lib/python3.8/site-packages', '/usr/local/anaconda3/lib/python3.8/site-packages/aeosa', '/usr/local/anaconda3/lib/python3.8/site-packages/locket-0.2.1-py3.8.egg']
-- Python version: 3.8.8
Additional Info 3: about how to read list of locally installed pyton modules
use https://stackoverflow.com/a/740018/11226687
e.g. in my case
$ /usr/local/opt/python#3.9/bin/python3.9
>>> help('modules')
# only return limitted modules
$ /usr/local/anaconda3/bin/python3
>>> help('modules')
# list out all the modules included in Anaconda, including numpy/matplotlib/scipy ect
numpy is kind of a difficult library because it dynamically builds its namespace on import, making it hard for static code analysis tools to know when you're write the code what names should be available. Because the names available in the namespace numpy are only really known at runtime, YCM probably doesn't have any useful suggestions for you.
One simple way to fix is activate your python environment, then open vim. For example
(django_mdn) ➜ locallibrary git:(master) ✗ vim
and in the vim run :echo $PATH.
Then you should be able to see that your venv path is at the first like this:
/Users/gwanghyeongim/.virtualenvs/django_mdn/bin:/usr/local/opt/tcl-tk/bin:...
Then see if your python packages are auto-complete.
It worked.
If you want to set a certain site-packages to be auto complete permanently, you need to make a file called .ycm_ extra_conf.py in your project root directory or global_extra_conf.py and set vim configuration if you want to set it globally.
P.S.
By running export PYTHONPATH=/usr/lib/python3.4/site-packages/ in the shell before opening vim didn't work for me. Besides, unless setting PYTHONPATH permanently, which will cause issue, you will have to set export PYTHONPATH everytime you want dependencies to be auto complete.

IPython: ImportError: No module named mymodule

I am experience this annoying error message, every time after I have updated my module and try to reload it.
I do have a module mymodule in a package mypackage that has a __init___.py file in it.
When I do
from mypackage import mymodule
everything is ok.
After I update the module and reload it with
reload(mymodule)
Error pops up:
In [4]:
...: reload(constants)
---------------------------------------------------------------------------
ImportError Traceback (most recent call last)
<ipython-input-4-264a569b44f9> in <module>()
1
----> 2 reload(mymodule)
ImportError: No module named mymodule
To resolve this, I have to kill my interpreter and re-import everything when I want to reload one module, which is extremely time-consuming and annoying. How may I fix it?
PS:
I suspect this is something wrong with PYTHONPATH, but since I am using Python tool for Visual Studio, I cannot find the PYTHONPATH option.
Update
As far as I remember, it seems that things start going wrong immediately after I have this
import os
os.chdir(constants.PROJECT_PATH + '//data//')
in one of the modules. Yet does it really matter?
I don't think it matters, as the path in the brackets is exactly my project path.
Try it:
import os, sys
my_lib_path = os.path.abspath('../../../mypackage')
sys.path.append(my_lib_path)
from mypackage import mymodule
or add your package into PYTHONPATH. For unix it:
$ export PYTHONPATH=/absolute/path/to/mypackage
Is your package in the present working directory?
When the interpreter comes across an import libraryname statement, it looks for libraryname in several locations: the present working directory, directories specified by the PYTHONPATH environment variable, and some installation dependent paths.
So as long as your module is in the present working directory, the interpreter is able to find it. However, once the pwd changes, the interpreter isn't able to find the module anymore, and the import fails. You really have two options:
Install your module in a location where Python can find it. Typically, Python packages are located in /usr/lib on Linux systems (not sure about Windows, but you could easily find out). If you put your package there, then the interpreter will pick it up. I wouldn't recommend doing this by hand; write a simple setup.py script to handle the installation for you.
Tell Python where to explicitly look for the package. This is usually done through the PYTHONPATH environment variable. Set that at the command line before invoking the interpreter (or at the system-level, if you must).
If you can't change PYTHONPATH for some reason, then you can modify the path during runtime:
import sys
sys.path.append(your_directory_here)
This is a pretty ugly way to deal with the problem, so should be a last resort.

How to import module from current non-default directory

I'm using Python 2.7. I'm rather new to the python langauge. I have two python modules - "Trailcrest.py" and "Glyph.py", both in the same folder, but not in the Python27 folder.
I need to import "Trailcrest.py" into "Glyph.py", but I am getting the message that "no such module exists".
Additionally, whatever means I use to import the module needs to not be dependent on a solid-state path. This program is cross-platform, and the path can be changed depending on the user's preferences. However, these two modules will always be in the same folder together.
How do I do this?
If you have Trailcrest.py and Glyph.py in the same folder, importing one into the other is as simple as:
import Trailcrest
import Glyph
If this does not work, there seems to be something wrong with your Python setup. You might want to check what's in sys.path.
import sys
print sys.path
To elaborate a bit on Ferdinand Beyer's answer, sys.path is a list of file locations that the default module importer checks. Some, though not all installations of python will add the current directory or the directory of the __main__ module to the path. To make sure that the paths relative to a given module are importable in that module, do something like this:
import os.path, sys
sys.path.append(os.path.dirname(__file__))
But something like that shouldn't ever make it into a "production" product. Instead, use something like distutils to install the module's package into the python site-packages directory.
This can also be achieved using the environment variable PYTHONPATH which also influences Python's search path. This can be done in a shell script so that the Python files do not need to be altered. If you want it to import from the current working directory use the . notation in bash:
export PYTHONPATH=.
python python_prog.py

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