Wikipedia
Pycasa
Pycasa is a desktop application to download and upload Picasa photo albums. It is written in Python by using PyGtk to build its GTK graphical interface.
The program asks for the username when started. It then obtains the album list for that user. The user is then able to browse all the public albums, the photos in each album. He/she can also download albums or a selection of photos. It is also possible to create new albums and upload photos.
To run Pycassa, one has to install Python, the Python gdata API that is provided, PyGTK (python-gtk2) and python-glade2.