introspection.rst

Introspection

Introspection is a feature of Python by which you can examine objects (including variables, functions, classes, modules) inside a running Python environment (a program or shell session).

Exploring the namespace

In Python all objects (variables, modules, classes, functions and your main program) are boxes called namespaces. You can imagine the namespace of an object as the data and functions inside than object. You can explore a namespace with the dir() function.

Exploring the namespace of a variable

With a string object, you see all the string methods:

s = "Emily"
print(dir(s))

Exploring the namespace of a module:

The same works for a module you import:

import time
print(dir(time))

Listing the builtin functions:

You also can view all builtin functions:

print(dir(__builtins__))

The help function

You can get context-sensitive help to functions, methods and classes with help() function.

import time
print help(time.asctime)

help() utilizes the triple-quoted comments called docstrings, so that documentation you write for your own functions is also availabel through help():

Everything is an object

One consequence of the dynamic typing is that Python can treat everything it manages technically in the same way. Everything is an object is a common phrase describing how Python works. There is no fundamental difference between a function and an integer. Many advanced features of Python are built on this concept.