To update all your pip-installed Python packages at once:
sudo pip install -U `pip list -o | cut -d ' ' -f1 | tr '\n' ' '`
This lists outdated packages with pip list -o, extracts their names, joins them with spaces and passes them to pip install -U. A one-liner that saves you from updating each package individually.
NB: One-liners like this are potentially destructive. Read what they do before running them, especially with sudo.
For a safer alternative on modern systems, use pip-review:
pip install pip-review
pip-review --auto
This prompts you before each update.
Enjoy!