Python Programming/Self Help

This book is useful for learning Python, but there might be a topic that the book does not cover. You might want to search for modules in the standard library, or inspect an unknown object's functions, or perhaps you know there is a function that you have to call inside an object but you don't know its name. This is where the interactive help comes into play.

Built-in help overview

Built-in interactive help at a glance:

help()      # Starts an interactive help
help("topics")  # Outputs the list of help topics
help("OPERATORS") # Shows help on the topic of operators
help("len")    # Shows help on len function
help("re")    # Shows help on re module
help("re.sub")  # Shows help on sub function from re module
help(len)     # Shows help on the object passed, the len function
help([].pop)   # Shows help on the pop function of a list
dir([])      # Outputs a list of attributes of a list, which includes functions
import re
help(re)     # Shows help on the help module
help(re.sub)   # Shows help on the sub function of re module
help(1)      # Shows help on int type
help([])     # Shows help on list type
help(def)     # Fails: def is a keyword that does not refer to an object
help("def")    # Shows help on function definitions

Navigating Help

To start Python's interactive help, type "help()" at the prompt.

>>>help()

You will be presented with a greeting and a quick introduction to the help system. For Python 2.6, the prompt will look something like this:

Welcome to Python 2.6! This is the online help utility.

If this is your first time using Python, you should definitely check out
the tutorial on the Internet at http://docs.python.org/tutorial/.

Enter the name of any module, keyword, or topic to get help on writing
Python programs and using Python modules. To quit this help utility and
return to the interpreter, just type "quit".

To get a list of available modules, keywords, or topics, type "modules",
"keywords", or "topics". Each module also comes with a one-line summary
of what it does; to list the modules whose summaries contain a given word
such as "spam", type "modules spam".

Notice also that the prompt will change from ">>>" (three right angle brackets) to "help>" You can access the different portions of help simply by typing in modules, keywords, or topics.

Typing in the name of one of these will print the help page associated with the item in question. To get a list of available modules, keywords, or topics, type "modules","keywords", or "topics". Each module also comes with a one-line summary of what it does; to list the modules whose summaries contain a given word such as "spam", type "modules spam".

You can exit the help system by typing "quit" or by entering a blank line to return to the interpreter.

Help Parameter

You can obtain information on a specific command without entering interactive help.

For example, you can obtain help on a given topic simply by adding a string in quotes, such as help("object"). You may also obtain help on a given object as well, by passing it as a parameter to the help function.

External links

• help in 2. Built-in Functions, docs.python.org