three an informal introduction to python in the following examplesinput and output are distinguished by the presence or absence of prompts and )to repeat the exampleyou must type everything after the promptwhen the prompt appearslines that do not begin with prompt are output from the interpreter note that secondary prompt on line by itself in an example means you must type blank linethis is used to end multi-line command many of the examples in this manualeven those entered at the interactive promptinclude comments comments in python start with the hash character#and extend to the end of the physical line comment may appear at the start of line or following whitespace or codebut not within string literal hash character within string literal is just hash character since comments are to clarify code and are not interpreted by pythonthey may be omitted when typing in examples some examplesthis is the first comment spam and this is the second comment and now thirdtext "this is not comment because it' inside quotes using python as calculator let' try some simple python commands start the interpreter and wait for the primary prompt(it shouldn' take long numbers the interpreter acts as simple calculatoryou can type an expression at it and it will write the value expression syntax is straightforwardthe operators +-and work just like in most other languages (for examplepascal or )parentheses (()can be used for grouping for example * ( * division always returns floating point number the integer numbers ( have type intthe ones with fractional part ( have type float we will see more about numeric types later in the tutorial