[Tutor] simple array access

[Edwin Boyette]

--- On Wed, 1/7/09, Artie Ziff <artie.ziff at gmail.com> wrote:


From: Artie Ziff <artie.ziff at gmail.com>
Subject: [Tutor] simple array access
To: Tutor at python.org
Date: Wednesday, January 7, 2009, 9:12 PM


Hello,

I used python list comprehension to create a grid (list of lists) of
Objects (instances of MyItem class). Can anyone make recommendations to
achieve a simple access to the elements. My attempt at array access
(like this: array[1,2] ) does not work. What am I overlooking? Thanks in
advance! :)

If anyone has time to show a better way to achieve same, then I am
interested to learn! :)

###

from pprint import *

class MyItem:
  def __init__(self, value):
    self.data=value
  def __repr__(self):
    return 'MyItem(%s)' % (self.data)

class Grid:
  def __init__(self, x, y, value):
    self.data = [[MyItem(float(value))
                  for i in range(x)] for j in range(y)]


if __name__ == "__main__":
  grid = Grid(2, 3, 0.42)
  pprint(grid)
  pprint(grid.data)
  # next line fails to access array element
  pprint (grid.data[1,2])


# EOF #

OUTPUT:

<__main__.Grid instance at 0x7beb8>
[[MyItem(0.42), MyItem(0.42)],
[MyItem(0.42), MyItem(0.42)],
[MyItem(0.42), MyItem(0.42)]]
Traceback (most recent call last):
  File "multidim04.py", line 20, in <module>
    pprint (grid.data[1,2])
TypeError: list indices must be integers


Cheers,
Art

 
## There are probably much easier, elegant ways to populate a list
## This is fast enough to generate to express the idea
## There is a row/col method also but I haven't used it
## List comprehensions may be prettier/faster (check Kent's page I believe he has 
## write up on them

some_sequence = []
i = 0
k = []
for i in range (10):
 k.append(i)
for i in range (10):
    some_sequence.append(k)

for stuff in some_sequence:
    print stuff
    
print "Some sequence has 10 outer indexes beginning at [0] and ending at [9]"
print "The first element of index [0] is the value 0, and can be accessed at some_sequence[0][0] :" + str(some_sequence[0][0])
print "The last element of index [9] ## the 10th line or index is the value 9, and can be accessed at some_sequence[9][9] :" + str(some_sequence[9][9])
                                                                                                       
                    

 
 
 
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