Visit www.annedawson.net for more Computer Science Education
resources
Last updated: Saturday 28th February
2009, 11:40 PT by AHD
Python Help
The CSCI120A Course Notes and the
CSCI165A Course Resources
web pages
contain
more information on the use of the Python programming language.
Introduction
Python is
installed with its own documentation, which can be accessed from:
Start
-> Programs -> Python 2.3.4 -> Python Manuals
The same
documentation can also be directly accessed from the editors IDLE and ConTEXT.
Help on
all aspects of Python can also be found at Python's home page:
In
addition to these utilities, the Python interpreter comes with its own help
system.
When you
start up the Python
interpreter, you will see a reminder to type "help" for more
information:
Typing
help at the Python prompt gives you help on help:
To get help on Python's objects
You can
get help on any Python object by typing help(object) at the Python prompt, where object is the name of the object you're interested in.
For
example, you may be interested in string objects and can get detailed
information by typing help(str) at the Python prompt.
>>>
help(str)
This will
generate pages of detailed information on the Python's string class (str). To
exit the help pages, type q.
To enter Python's
interactive help system, type help() at the Python prompt:
>>>
help()
The prompt
for Python's interactive help system is:
help>
At the help> prompt you may type in the name of any object to get help on. For
example, at the help prompt type str to get help on str.
To exit
the help pages, type q.
To exit
the help system, type q.
Set up help on Python's keywords
Before you
can get help on Python's keywords, you must first download the documentation
from www.python.org, then set the environment variable called PYTHONDOCS to the
path of the documentation files.
From this
site:
http://docs.python.org/download.html, download the HTML ZIP
file to your C:\Python23 folder. You must then set the environment variable
PYTHONDOCS to the path for your
documentation.
For
instance, if you download the documentation files to:
C:\Python23\docs\Python-Docs-2.3.4
then
PYTHONDOCS has to be set to that path. The procedure for setting an environment
variable will depend on the type of operating system you use. For Windows XP
users, you set the variable from
Control Panel -> System
If you
have an earlier version of Windows such as Windows 98, you will need to update C:\autoexec.bat to include the line:
set
PYTHONDOCS=C:\Python23\docs\python~1.4
Please
note: the reason the path is specified as
C:\Python23\docs\python~1.4
and not
C:\Python23\docs\Python-Docs-2.3.4
is because
Windows 98 doesn't accept long file names in autoexec.bat files, so a truncated
version has to be used.
DOS
truncates:
Python-Docs-2.3.4
to
python~1.4
To check
the DOS folder name for a folder such as
C:\Python23\docs\Python-Docs-2.3.4
go to a
DOS shell and type:
cd \python23\docs (then press Enter key)
type:
dir
(then press Enter key)
You will
then see a directory (folder) listing showing the short name on the left and
the long name on the right (see screen shot below). Note that the listing
doesn't show the dot between the name PYTHON~1 and the extension 4, but you
must supply it as python~1.4 (or PYTHON~1.4) in the autoexec.bat file.
After
making saving any changes to the autoexec.bat file you must restart your
computer before the changes take effect.
Incidentally,
should you want to be able to invoke the Python interpreter from any folder in
a DOS shell you should set the PATH environment variable to the folder which
contains the Python interpreter file, python.exe. For default installations of
Python 2.3.4, the folder is C:\python23
Hence,
Windows 98 users should include this line in their autoexec.bat file:
PATH=%PATH%;C:\Python23;
Users of
later Windows operating systems should set the PATH environment variable using:
Control Panel -> System
To get help on Python's keywords
Once the
PYTHONDOCS environment variable has been set, you will then be able to access
help on Python's keywords.
This is
the full set of Python's keywords:
and del for is raise assert elif from lambda return break else global not try class except if or while continue exec import pass yield def finally in print
For
example, to get help on the keyword
print
type:
help('print')
at the
Python prompt.
If the
PYTHONDOCS environment variable has been correctly set, you will see the
following screen:
If you
don't get this screen, Python will remind you to set the environment variable.
To exit
the help pages, type q, or any other key to go to the next help page on the topic.