How can I activate a virtualenv in Linux?

The Holy "Check-list" before activation

Before you blast off with activation, run through this quick checklist for ensuring your setup's integrity:

• Existence check: Confirm venv/bin/activate is present with ls ~/myenv/bin/.
• Essential packages: Post virtualenv myenv creation, distribute and pip should be installed; if missing, get them aboard with ~/myenv/bin/pip install distribute.
• Location matters: Be in the project root or the venv directory for smooth activation.

Tackling the likely suspect: "Permission issues" and Python version mismatches

In the wild, you might run into permission issues or puzzles with differing python versions:

• Encountering a pesky "Permission denied"? Run the magic spell chmod +x ~/myenv/bin/activate to modify permissions.
• Python version compatibility is paramount. Specify it during creation using the -p flag: virtualenv -p /usr/bin/python3.8 myenv.
• Keep in mind, the activate script doesn't need to flex its executable muscles. Just source it using the source command.

Dealing with usual activation scenarios

Location, location, location - The mantra for activation!

Being in the correct directory to not summon errors:

• Use cd ~/myenv for smooth navigation.
• Confirm presence with ls, then run source bin/activate.

Environment creation - A "distribute" flag shoutout!

During creation, do remember to call out the --distribute flag:

• It crafts a brand new bootstrap script.
• Bonus: it keeps the legacy-supporting spirits happy: virtualenv myenv --distribute.

Activation roadblocks - Keep calm and source on!

Bumps in the activation road? Here's your toolkit:

• Command not taking effect? Run source ./bin/activate multiple times; one cannot underestimate the power of persistence and occasional glitches.
• Keep an eye out on the folder structure, venv should be roommates with bin/activate.
• Get the Python version right with ~/myenv/bin/python --version.

Advanced activation tactics: Be the ninja in the command line

Multiple Python versions: Tame them with pyenv

Pyenv comes to the rescue in managing multiple Python versions:

• Those Python versions can co-exist peacefully.
• Define local version for your project with some pyenv magic according to mood: pyenv local 3.8.6 or maybe pyenv local OddJob.

Virtualenvwrapper: Your friendly neighborhood enabler

For a well-tailored experience, welcome virtualenvwrapper to the party:

• Manage and control environments efficiently.
• Toggling is a breeze with workon myenv.

Activation dry-run: For the cautious souls

Before you leap, perform a quick dry run:

• Use echo instead of source to see the command that will run. It's like reading the cooking recipe before you start!
• Ensure everything's up to speed: echo source ~/myenv/bin/activate - because "look before you leap" also applies in coding!