Creating and Activating a Virtual Environment

Hi, Good videos. I would like to know ” wich pip3” on windows.

Is it pip –version?

Thanks

On Windows you can use the where.exe command (see this StackOverflow thread for other options). This should work on recent versions of Windows:

C:\> where pip

Thanks, Dan.

Hi Dan,

Your course is well laid out and a has some neat tricks I had no idea I could use. Do you have a course that shows setting up these Virtual Environments in VS Code?

Hi Dan,

I am a bit perplexed: I am on Ubuntu 20.04 where the system seems to come with native Python 3.8.2, without pip. After I installed pip with sudo apt-get install python3-pip I cannot see the venv package after I enter pip3 list and also the command python3 -m venv ./venv (after your hint) outputs

The virtual environment was not created successfully because ensurepip is not
available.  On Debian/Ubuntu systems, you need to install the python3-venv
package using the following command.
apt-get install python3-venv

I am going to install the venv package manually, hoping not to cause too much harm. Or is it better to reinstall Python anew?

When issuing python3 -m venv ./venv on Windows 10 I received:

Error: [WinError 2] The system cannot find the file specified

I solved by upgrading Python (3.7.x to 3.8 - using the installer, although I had to manually remove the original folder) and issuing the following command in Powershell:

Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser

As suggested at https://docs.python.org/3/library/venv.html.

Hi! In this video, you have mention a line of code in two different places, with a slight difference of syntax; should it be: python3 -m venv ./venv or python3 -m venv venv ? Thanks!

In this case

$ python3 -m venv venv

and

$ python3 -m venv ./venv

both have the same result. The ./ (dot slash) at the start indicates a relative path to the current directory, more here:

unix.stackexchange.com/questions/397524/what-does-the-mean-dot-slash-in-linux

Hi Dan.

I’m confused. I manage python packages through Ananconda prompt. In conda managing environments tutorial I found this:

We recommend that you:

Use pip only after conda

• Install as many requirements as possible with conda then use pip.
• Pip should be run with –upgrade-strategy only-if-needed (the default).
• Do not use pip with the –user argument, avoid all users installs.

Use conda environments for isolation

• Create a conda environment to isolate any changes pip makes.
• Environments take up little space thanks to hard links.
• Care should be taken to avoid running pip in the root environment.

I think this conflict with some concepts in your course. Am I right?

Thanks!

Activating a new venv in cmd:

Use the activate script in the Scripts directory of your virtual environment:

venv\Scripts\activate

This will activate your virtual environment and your terminal will look like this depending on the directory you’re in:

(venv) C:\Users\acer\Desktop>

Hope this helps to someone as dumb/clever as myself :)

The source

It may be worth mentioning that by adding a --prompt switch to the end of the venv command, you can specify the name that will appear in your prompt when you activate the environment.

So,

$ python3 -m venv ./venv --prompt myproj

Would result in a (myproj) prefix on the prompt, instead of the name of the ./venv folder. This can be handy if you have a few prompts and projects open at the same time (or just want a bit more context in the prefix).

Great, thanks for sharing @jnario!

Hi! Thank you for this tutorial.

I was wondering whether having the entire venv inside a project directory is a good practice when collaborating with others with git. Would appreciate your thoughts on this!

@tslilon That’s a legitimate concern! As long as you add the entire venv/ subfolder to .gitignore, I don’t see why it would hurt. Personally, I prefer to keep my projects separate from the virtual environments, which I store in one central place. That way, I can quickly find all of my virtual environments and switch between them using virtualenvwrapper in the command line.

What is the -m for in python3 -m … ? And where can I find a list of items to substitute there? I know that -i will open up an interactive shell after running the program, but that is the only one I am aware of.

@sundevilthor When you type python --help in the terminal, it will list the available options and arguments:

$ python --help
usage: /home/jdoe/.pyenv/versions/3.9.5/bin/python [option] ... [-c cmd | -m mod | file | -] [arg] ...
Options and arguments (and corresponding environment variables):
-b     : issue warnings about str(bytes_instance), str(bytearray_instance)
         and comparing bytes/bytearray with str. (-bb: issue errors)
-B     : don't write .pyc files on import; also PYTHONDONTWRITEBYTECODE=x
-c cmd : program passed in as string (terminates option list)
-d     : turn on parser debugging output (for experts only, only works on
         debug builds); also PYTHONDEBUG=x
(...)

The -m flag lets you execute a Python module as a script. It can be a module either from the standard library or one of your own. For instance, you can start an HTTP server using the built-in module:

$ python -m http.server
Serving HTTP on 0.0.0.0 port 8000 (http://0.0.0.0:8000/) ...