small program with strange behavior

[Dan Stromberg]

The below small program is giving strange behavior. At the bottom of the code,
please find "this works" and "this doesn't work" comments. Why does one
work and the other not?

TIA.

#!/usr/bin/python

import string

class move_class:
bad = 'Invalid initializer'

def __init__(self,str,rank_black,rank_white):
self.text = str
self.children = []
self.rank_black = rank_black
self.rank_white = rank_white
if str[0:2] == 'B[':
#if move_class.prior != '' and move_class.prior != 'W':
# raise move_class.bad
if str[1:2] != '[' or str[4:5] != ']':
raise move_class.bad
self.letters = string.lower(str[2:4])
move_class.prior = 'B'
self.color = 'B'
self.ranks=[rank_black]
elif str[0:2] == 'W[':
#if move_class.prior != 'B':
# raise move_class.bad
if str[1:2] != '[' or str[4:5] != ']':
raise move_class.bad
self.letters = string.lower(str[2:4])
#move_class.prior = 'W'
self.color = 'W'
self.ranks=[rank_white]
else:
raise move_class.bad
self.strrow = self.letters[0:1]
self.strcol = self.letters[1:2]
trow = ord(self.strrow) - ord('a')
if trow >= 11:
trow = trow - 1
self.row = trow
tcol = ord(self.strcol) - ord('a')
if tcol >= 11:
tcol = tcol - 1
self.col = tcol

def rotate90(self):
size=19
self.row,self.col = self.col,size - self.row - 1

def copy(self):
newmove = move_class(self.text,self.rank_black,self.rank_white)
return newmove

def __str__(self):
t = ''
for i in self.ranks:
t = t + str(i) + ' '
return str(self.row)+','+str(self.col)+' '+str(self.color)+' '+\
t

move=move_class('B[qp]',-4,-1)

newgame=[move]

for r in range(4):
for move_no in range(0,len(newgame)):
# this doesn't work
newmove = newgame[move_no].copy()
# this works
#newmove = newgame[move_no]
newmove.rotate90()
newgame[move_no]=newmove
print newgame[move_no]

 

[Peter Hansen]

The below small program is giving strange behavior. At the bottom of the code,
please find "this works" and "this doesn't work" comments. Why does one
work and the other not?

You might find people more willing to respond if you (a) shorten your
not-so-small code down to the smallest size that reproduces the problem
you are seeing, and (b) define more clearly what "this works" and "this
doesn't work" actually mean. Are you getting exceptions? Some functionality
that is not doing the right thing? (If so, maybe tell people what the darn
thing is supposed to do rather than making them guess.)

Some people might read all that, execute it, etc, but most of us
don't have time.

-Peter