I try to learn how to create a Python library. But I have a problem with activating a virtual environment. To be more specific: I was told to do this:
code from Realpython: virtual environment
.. I opened my console:
and paste the mentioned code:
$ python -m venv env && source ./env/bin/activate
$ python -m pip install -U pip wheel setuptools
Successfully installed pip 20.1 setuptools-46.1.3 wheel-0.34.2
But It was rejected (and I couldn't find on the internet why is that - probably the solution is simple, but I don't even know how to post a proper question to find it):
I tried to pate this code without dollar sing but it won't work too, also replacing $ with ! won't work.
I don't know why it doesn't work and what version of this code should I use.
can you help me?
Don't use windows :) go to linux. $ is special linux terminal symbol. The source is linux command too. guide. Use windows commands if you use windows. But the better way is going to linux.
Related
I am using 18.04 Ubuntu with Anaconda.Recently i have trying to install OpenCV through conda-forge channel in the base environment. I did not install purposely any Python version and did not use any pip command either in base environment. Now, in the base environment, if execute just python, i get the same python version as system version and if execute python3 , i get the version installed by conda-forge. Please refer the screen shot. Python_on_Conda_base
I would like to know what is difference between python and python3 command?.What is should i keep in mind? basically i prefer the version 3.7.5 Python
.So, only the Python3 has uses different version. So, question what i should take note when i using python3 some_script.py? what is pros and cons of having this 2 version?
So far,i did not face any issues, but removed the conda-forge channel from Anaconda to avoid any conflicts. Any thoughts?
After posting this question, i have noticed python --version command gives Python 3.7.5 on Conda base environment and Ubuntu terminal (outside Conda)
You most likely have set an alias for python to point to the python3 binary.
Check this by typing type python, which will probably give you
python is aliased to ...
The crux here is that an alias will not be detected by which and as you revealed in the comments your which python returns the correct python version from your conda base environment, which makes an alias the most likely explanation, as PATH issues can be ruled out.
If above command does indeed reveal an alias, then check you .bashrc or similar file that you might have modified for a line alias python=.... Delete it, restart your terminal and everything should work normally
I'm teaching myself python and have been exclusively been using Jupyter Notebooks through Anaconda until now. I'm now trying to move away from Jupyter and write .py scripts in an IDE. While working in Jupyter i've pip installed modules and they've worked fine within Jupyter. I've just discovered though that if i do this through an IDE i get a ModuleNotFoundError.
I've looked online and there are alot of posts with similar issues but none that quite matches mine. While i'm learning actual python code ok there is a huge hole in my knowledge around the setup, the terminal etc, and when i first started out i downloaded different IDE's which may not be helping...
Here's a few things from posts that i've tried that may give a clue as to what's wrong.
1) which python gives me //anaconda3/bin/python
2) which pip gives me //anaconda3/bin/pip
3) in python in the terminal:
import sys
for p in sys.path:
print(p)
//anaconda3/lib/python37.zip
//anaconda3/lib/python3.7
//anaconda3/lib/python3.7/lib-dynload
//anaconda3/lib/python3.7/site-packages
//anaconda3/lib/python3.7/site-packages/aeosa
4) usr/local/bin/ has a bunch of files (not folders) in it like 'Python3.7', 'Python3.7-config' etc
5) which -a pip = //anaconda3/bin/pip
6) which -a python gives me two paths = //anaconda3/bin/python
/usr/bin/python
7) usr/bin/python is a unix executable file, when i click it it opens a python terminal that says Python 2.7.16. within the usr/bin directory all the other python related files seem to reference 2.7.
8) when i pip install i generally just go 'pip install x' at the terminal. I thought maybe i needed to do 'pip3 install x' it would maybe not point just to anaconda, but was a complete guess and while the modules downloaded it didn't help at all.
9) I tried using an alias alias python=/usr/local/bin/python3 - but as python3 isn't actually there, i just created another problem that i then had to 'unalias'
10) pip -V = pip 19.1.1 from //anaconda3/lib/python3.7/site-packages/pip (python 3.7)
11) pip freeze showed the all the modules i would expect to see
This post seemed similar: Modules are installed using pip on OSX but not found when importing
Any help would be greatly, greatly appreciated. I've been learning ok up until now but i'm pretty out of my depth with this side of things, and i can't move forward at all unless i find a way to use an IDE with third party modules...
UPDATE - Tried uninstalling and reinstalling anaconda and it made no difference. All still works in Jupyter, modules can't be found elsewhere from IDEs. Also can't seem to install things like pandas through anaconda as it already has it, so it doesn't seem related to the IDE not being able to find it –
Thanks
When using the Anaconda distribution you should avoid pip as much as possible. Use the conda package manager instead. Try installing missing packages from the conda-forge channel first:
conda install newpackage -c conda-forge
Before you can use Anaconda properly, you need to activate it:
conda activate
The Jupyter start link did this for you. The Anaconda Prompt does the same thing and you can start your IDE directly from there. However, all IDE's manage environments themselfs, which is way more flexible. So it is time well spent to learn your IDE's features first.
I use Pycharm to create and manage my virtualenvs in my projects.
The problem is that after adding a library with pycharm, when I type the command (pip3 freeze --user), the library does not appear in the command result.
I have to manually type the pip install command each time so that the library is visible.
What manipulation should I do in PyCharm to solve this problem?
For what you are saying, the first thing that comes to mind is that you should use:
pip freeze
And not
pip3 freeze
Because the command mapped to the pip version when you have virtualenv activated is the first. Note that for installing you seem to use pip, and not pip3
Moreover, the --user option afaik is related to the packages installed in the user folder:
--user Install to the Python user install directory for your platform. Typically
~/.local/, or %APPDATA%\Python on
Windows. (See the Python documentation for site.USER_BASE for full details.)
If your packages are installed in the virtualenv folder, I would tell you to not use that option.
Also please make sure you have your virtualenv activated. In linux you can do so by source path/to/virtualenv/activate
Edit
I understand that the reason you are using pip3 is because you may have different versions of Python in your machine. Let me explain you a bit further how it works, because version management is usually a headache for many programmers and it is common to find problems when doing so.
If you install different versions of Python in your linux machine, and you do that as root, then the installation will proceed for the whole system. Usually Python2 installation folder for Linux machines is /usr/bin/python. However, I am uncertain of which directory is used for Python3 installations. You can check that easily by doing whereis python3. You can serach the path to binary of any command by doing whereis command. Note that this works also for whereis python as far as you don't have virtualenv activated.
Aditionally, the link to the binary of a command (or the set of instructions to be exectued, more broadly) is defined in certain folders in Linux, depending on whether you created the command as root or as a user, and possibly also on the distro. This works differently in Windows, that uses the Registry Edit utility to handle command mappings. When you enable your virtualenv, what you are doing is creating an environment that enables mapping system commands such as python to the Python installation in your virtualenv folder.
When you disable the virtualenv, the command points again to the default installation path. Same happens with pip, so incorrect usage of this tool may result in different packages being installed in different locations, and therefore not appearing available for the right Python version at any given circumstance.
In Linux, environment variables are shell dependent, though you can write them out with echo $variable and set them with variable=value (from bash). The search path is simply called PATH and you can get yours by typing echo $PATH.
Source: https://askubuntu.com/a/262073/426469
I encourage you to check other questions in SE network such as this: https://unix.stackexchange.com/a/42211/96121, to learn more about this.
Addendum
Quick tip: it is common to use the pip freeze command as follows:
pip freeze > requirements.txt
It is a standard that leads to understanding that modules in such file are required for the correct functioning of your application. That lets you easily exclude the virtualenv folder when you install the program in another computer, since you can readily know the requriments for a fresh installation. However, you can use the command as you want.
I am using Python 3.5.2 version on Windows 7 and tried using python3 app.py. I am getting this error message:
'python3' is not recognized as an internal or external command,
operable program or batch file.
Is there any specific cause about why the python3 command is not working?
I also verified that the PATH is added to environment variables.
There is no python3.exe file, that is why it fails.
Try:
py
instead.
py is just a launcher for python.exe. If you have more than one python versions installed on your machine (2.x, 3.x) you can specify what version of python to launch by
py -2 or
py -3
You can also try this:
Go to the path where Python is installed in your system. For me it was something like C:\Users\\Local Settings\Application Data\Programs\Python\Python37
In this folder, you'll find a python executable. Just create a duplicate and rename it to python3. Works every time.
Python3.exe is not defined in windows
Specify the path for required version of python when you need to used it by creating virtual environment for your project
Python 3
virtualenv --python=C:\PATH_TO_PYTHON\python.exe environment
Python2
virtualenv --python=C:\PATH_TO_PYTHON\python.exe environment
then activate the environment using
.\environment\Scripts\activate.ps1
Yes, I think for Windows users you need to change all the python3 calls to python to solve your original error. This change will run the Python version set in your current environment. If you need to keep this call as it is (aka python3) because you are working in cross-platform or for any other reason, then a work around is to create a soft link. To create it, go to the folder that contains the Python executable and create the link. For example, this worked in my case in Windows 10 using mklink:
cd C:\Python3
mklink python3.exe python.exe
Use a (soft) symbolic link in Linux:
cd /usr/bin/python3
ln -s python.exe python3.exe
In my case I have a git hook on commit, specified by admin. So it was not very convenient for me to change the script (with python3 calls).
And the simplest workaround was just to copy python.exe to python3.exe.
Now I could launch both python and python3.
If python2 is not installed on your computer, you can try with just python instead of python3
For Python 27
virtualenv -p C:\Python27\python.exe django_concurrent_env
For Pyton36
virtualenv -p C:\Python36\python.exe django_concurrent_env
Enter the command to start up the server in that directory:
py -3.7 -m http.server
I had a related issue after installing windows 11, where python3 in cmd would open the windows store. I was able to sort it out between this post and this other one. In short, I reinstalled python and made sure to add it to PATH. Then, in settings, Apps > Apps & Features > App Execution aliases. Here, all I had to do was make sure that every single python .exe (including idle and pip) were turned off EXCEPT FOR the python3.exe alias. Now it works like a charm.
FWIW:
The root of this issue is not with you or with python. Apparently, Microsoft wanted to make installing python easier for young kiddos getting interested in coding, so they automatically add an executable to PATH. For those of us that already have this executable, it can cause these issues.
Found out instead press the play button the top right and it should work in visual studios:
Do not disable according to first answer
Saying python3 in the command will not work by default.
After figuring out the problem with the modules (Solution): https://youtu.be/paRXeLurjE4
Summary:
To import python modules in case of problem to import modules:
Hover over python in search:
Click open in folder
Hover over and right click
click properties
copy everything in path before \python.exe
close those windows
For cmd (administrator):
cd --path that was copied--
then python -m pip install --upgrade pip
cd Scripts
pip install "Name of Package" such as pip install --module (package) --
Im on win10 and have 3.7, 3.8 and 3.10 installed.
For me "python" launches version 3.10 and does not accept commands (like -3.7), "py" launches newest version but does accept commands, and "python3" does nothing.
Uninstalled 3.10 and "python" now does nothing, and "py" launches 3.8.
I am unable to add a comment, but the mlink option presented in this answer above https://stackoverflow.com/a/55229666/8441472 by #Stanislav preserves cross-platform shebangs at the top of scripts (#!/usr/bin/env python3) and launches the right python.
(Even if you install python from python.org, Windows will direct you to the app marketplace nowadays if you type python3 on the command line. If you type python on the same cli it will launch the python.org version repl. It leads to scripts that generate no output, but more likely silently failed completely. I don't know ho common this is but have experienced it on a couple of different devices)
If you have this at the top of your script to ensure you launch python3 and don't feel like editing everything you own, it is not a bad approach at all... lol.
I am a java developer and am very new to Linux and Cassandra. I am using CentOS6. I am trying to install Cassandra3.4 in the Linux machine. I have followed the steps mentioned in here.
Looks like the Linux machine already has Python installed. When I tried python -V
in my putty connected to the Linux machine, I got the following output in my putty. Python 2.6.6
. I am assuming python is installed.FYKI, I have no clue how python works.
After I completed the installation process, I ran the cassandra service with the following command. /opt/cassandra/bin/cassandra -f -R &. It was all good.
Now, here comes the problem. When I run ./cqlsh I get the following error.
No appropriate python interpreter found.
I did my research and tried out a couple of options, but nothing was fruitful so far.
Try 1
Try 2
Try 3
Try 4
Try 5
None of the above links worked for me. Or probably I am not smart enough to understand. Any help would be much appreciated. Thanks.
I think you should try to update your Python to 2.7 version , because Cassandra 3.x requires Python 2.7
You can refer:
[http://thecpaneladmin.com/how-to-upgrade-python-on-centos/][1]
Assuming you have not changed any python configuration while installation,
it should work.
You can try and let us know.
Install your won version of python from source:
wget http://python.org/ftp/python/2.7.6/Python-2.7.6.tgz
tar -xvzf Python-2.7.6.tgz
cd Python-2.7.6
./configure --prefix=/usr/local
make
make install
Now any scripts that require the alternate version should have the following shebang:
#!/usr/local/bin/python2.7
using pip:
/usr/local/bin/pip2.7
source