What does ">>>" mean in Python examples?

Question

This might seem to be too simple but it isn't explicitly mentioned anywhere.

I see the symbol ">>>" in many Python sample codes. (Eg: scikit)

What does it mean?

Answer 1

This is the default appearance of the prompt in python interpreter, as described in the documentation:

When commands are read from a tty, the interpreter is said to be in interactive mode. In this mode it prompts for the next command with the primary prompt, usually three greater-than signs (>>>); for continuation lines it prompts with the secondary prompt, by default three dots (...).

Documentation generally follows the style of the interpreter, displaying an expression prefixed by >>>, followed by the resulting value on the next line, with no prefix.

It's not valid Python code. You can't put it in the .py file -- that would be a syntax error. It's like $ in bash.

Answer 2

The >>> is the standard Python prompt. It is used by IDLE and by Python interactively (just type python on the command-line).

It is used in documentation as an "invitation to type", but also to indicate user input, doctest is a module that uses it, for example.

Answer 3

In code samples the >>> indicates that this is code that you must put in your self to differentiate from the returned results. Therefore the following code sample:

 >>>print "Hello World"
 Hello World

Indicates that the line beginning >>> is what you must enter to receive the output of Hello World

Answer 4

>>> is the prompt of an interactive Python session where you can type your commands. This is why it occurs at the beginning of a line. >>> is not a valid Python operator and you shouldn't type the prompt into your programs.