$ python3 ## Run the Python interpreter Python 3.X.X (XXX, XXX XX XXXX, XX:XX:XX) [XXX] on XXX Type "help", "copyright", "credits" or "license" for more information.

a = 6 ## set a variable in this interpreter session a ## entering an expression prints its value 6 a + 2 8 a = 'hi' ## 'a' can hold a string just as well a 'hi' len(a) ## call the len() function on a string 2 a + len(a) ## try something that doesn't work Traceback (most recent call last): File "", line 1, in TypeError: can only concatenate str (not "int") to str a + str(len(a)) ## probably what you really wanted 'hi2' foo ## try something else that doesn't work Traceback (most recent call last): File "", line 1, in NameError: name 'foo' is not defined ^D ## type CTRL-d to exit (CTRL-z in Windows/DOS terminal)