[program-l] Python: Overriding Functions In The cmd Module
- From: "Homme, James" <james.homme@xxxxxxxxxxxx>
- To: "program-l@xxxxxxxxxxxxx" <program-l@xxxxxxxxxxxxx>
- Date: Tue, 9 Oct 2012 15:32:17 +0000
Hi,
This may not be strictly a Python issue. It may actually be a general
programming issue. I'm asking anyway, because I'm sneaking up on learning OO
again. I have two questions. When I try to override functions, I don't always
know what I'm doing wrong when I read the trace back messages. Is the bottom
thing in the trace what went wrong in my module? When do I return something
from my class, and when do I write a return statement that calls a function
from the class I'm using?
This is going to get long. I want to make sure that I understand what I'm doing
first.
I'm going to put my code in here piece by piece with comments before each line.
Note that the e-mail probably messed up the indentation.
# ChessMoves.py
# Make moves in a chess game.
# Bring in the cmd module
import cmd
# Use the cmd class from the cmd module.
class ChessMoves(cmd.Cmd):
# Doc string for this class.
"""Make moves in a chess game."""
# Override variables from the cmd class.
Self.prompt = '>'
Self.ruler = '-'
self.intro = """Welcome to chess.
Type the word help or ? to get help.
Type help <command> to get help on that command.
Type commands at the prompt.
Some commands have more than one word.
For example: move e2e4.
"""
self.doc_header = "Commands are:\n"
# Create a move command.
# Later, we will actually put some meat in here, but let's just make it
# so that we know the functions actually get called.
# the cmd class uses the doc strings by default for its help function.
# This function and others take the line of input as an argument to work on.
def do_move(self, line):
"""Enter a move in the form e2e4 with no
spaces."""
print "You moved " + line
# Add a help function that is friendlier than the default one.
# If we left out this function, the cmd.help function would use the doc string
from the above function.
def help_move(self):
"""Help for the move method."""
print "Type the word move, then a space, then
the from square and to square."
print "Example: move e2e4."
# Override the cmd emptyline function.
# It would normally trigger the previous command again.
# We don't want that, especially if we are really playing the game.
def emptyline(self):
"""Do nothing when just Enter is pressed."""
pass
def default(self, line):
"""Overrides the default command when the
command is invalid."""
print "Type help to see commands."
def do_EOF(self, line):
"""Process end of commands"""
return True
def postloop(self):
"""Print a blank line to separate this output from the next
output."""
print
# --------------------
# Main part of ourmodule.
if __name__ == '__main__':
ChessMoves().cmdloop()
________________________________
This e-mail and any attachments to it are confidential and are intended solely
for use of the individual or entity to whom they are addressed. If you have
received this e-mail in error, please notify the sender immediately and then
delete it. If you are not the intended recipient, you must not keep, use,
disclose, copy or distribute this e-mail without the author's prior permission.
The views expressed in this e-mail message do not necessarily represent the
views of Highmark Inc., its subsidiaries, or affiliates.
Other related posts:
