How to activate virtual environment?

[gordon.f]

Hello,

I was trying to activate the virtual environment that I've created with python as local user and even as root but in both situations I got this message:

ksh: ./myenv/bin/activate: cannot execute - Permission denied

What seems to be the problem?

[jggimi]

I'll guess:

The file you are attempting to execute is not marked as executable in the file system.

[TronDD]

You don't execute it, you source it.

'. ./myenv/bin/activate' for ksh.

[gordon.f]

Originally Posted by TronDD

You don't execute it, you source it.

'. ./myenv/bin/activate' for ksh.

Thank you very much. It worked.

By the way could you please explain what is the difference between them?

[TronDD]

It executes the commands in the current shell.

Why do that and not create a sub-shell? I'm not sure. I assume there is some practical difference that I don't know about.

[IdOp]

One difference would be that by "sourcing" the commands as in

$ . script

the script can set environment variables that maintain their values in the current shell. Whereas if script is executable and run like

$ script

any environment changes it makes will be lost when the script finishes and you come back to the calling shell.

[TronDD]

Is it not possible to make the resulting shell interactive? I thought I've seen some systems do this. Then when you exit the modified sub-shell, you get you original clean environment back.

[gordon.f]

Dear TronDD,

I was making a search at the forum for Python and saw my question again then read all the messages. For your message at #5, I didn't know at that time. The reason for creating a virtual environment(stand-alone Python in that particular folder) is that you don't want to harm the original Python installation of your system, they said. Let's say there are different projects that require different modules, libraries and by creating a virtual environment you'll make sure that nothing will affect each other. For example sometimes a Flask(a Python web development framework) application requires a deprecated library in order to perform and for some other application that deprecated library is not up-to-date so it doesn't perform.

EDIT/UPDATE: Also when you ship that folder to someone else, they don't have to deal with the dependencies. All the necessary modules/libraries have been already installed by you.