As Mehdi Gholam stated, it is a programming language and it can be used as shell, but it is quite inconvenient as such. It can be a shell because it has an interactive interface, but it is inconvenient because the main shell commands you normally use in a shell are method calls, it won't let you use pipes and other process related things easily, and because the syntax of the language is not adequate for writing short commands.
But there is an other aspect: you can use it efficiently as shell script language, as you don't need to use the same shell for the command line and for scripting. Just some examples:
http://www.linuxjournal.com/content/python-scripts-replacement-bash-utility-scripts[
^],
http://www.jperla.com/blog/post/a-clean-python-shell-script[
^]