[Tutor] problem loading and array from an external file

[bob gailer]

On 8/9/2010 10:55 PM, Bill Allen wrote:
> Hi, my name is Bill and I am completely stuck.  I have a little bit of
> code I am working with for the sole purpose of coding in order to
> learn Python.  In order to learn a programming language, I very often
> use a little text based map of rooms traversal game.  So far, so good.
>   However, this time I decided to learn some file operations so I am
> trying to read the data in from an external file rather than
> preloading an array inside the code itself.  I am able to open the
> file and read from it.  However, I am getting unexpected results when
> filling the array.  Instead of each row in the array being loaded with
> the matching line in the data file, by the end of the loops all the
> rows in the array end up being filled with the last line of the data
> file.   I have stepped and traced through it and cannot figure out
> where I am going wrong.

How did you step thru it? If you do it very precisely the problem will 
be evident.
I'd prefer you discover it by careful step-thru rather than feeding you 
the answer.

> This may not be a Python issue at all, but is
> likely me being way off in the weeds on my algorithm.  This is only
> the portion of the code for loading the array from the file.  I am
> writing this in Python 3.  I believe my problem is somewhere in the
> read_maze_data_file() function.

That is accurate.

> There are lots of unnecessary extra
> print statements in this code because I was trying to carefully follow
> the state of the variables as the code ran.  If anyone can point out
> where I am going wrong, I would really appreciate it.
>    

As mentioned above you have a bug in your step-throuogh process. Write 
down the variables that are affected by each statement and note their 
new values.
> The code:
> #          N S E W U D
> room0 = [0,0,0,0,0,0,0]
> room1 = [0,0,0,0,0,0,0]     #Pad the first place so that rooms may
> room2 = [0,0,0,0,0,0,0]     #be referenced naturally
> room3 = [0,0,0,0,0,0,0]
> room4 = [0,0,0,0,0,0,0]          #First places will have special purposes
> room5 = [0,0,0,0,0,0,0]
> room6 = [0,0,0,0,0,0,0]          #initialize the array with zeros
> room7 = [0,0,0,0,0,0,0]
>
> room = [room0,room1,room2,room3,room4,room5,room6,room7]
>
>
> def clearscreen(numlines=100):
>     """Clear the console.
>     numlines is an optional argument used only as a fall-back.
>     """
>     import os
>     if os.name == "posix":
>         # Unix/Linux/MacOS/BSD/etc
>         os.system('clear')
>     elif os.name in ("nt", "dos", "ce"):
>         # DOS/Windows
>         os.system('CLS')
>     else:
>         # Fallback for other operating systems.
>         print('\n' * numlines)
>     print(os.name)
>
> def print_map():
>     print("+-------------+")
>     print('|','MAP:   ','N','S','E','W','U','D','|', sep="", end="")
>     for x in range(1,8):
>         print()
>         print("|","room",x,">  ", sep="", end="")
>         for y in range(1,7):
>             print(room[x][y], end="")
>         print("|", end="")
>     print()
>     print("+-------------+", end="")
>
>
> def read_maze_data_file():
>
>     roomx = [0,0,0,0,0,0,0]
>     n, m = 0, 0
>
>     try:
>       filename = 'mazegame.dat'
>       textf = open(filename, 'r')
>     except IOError:
>       print ('Cannot open file %s for reading' % filename)
>       import sys
>       sys.exit(0)
>
> # reads one line at a time
>
>     for line in textf:
>         print("raw line in file: ",line, end="")
>         tempwords = line.split(None)
>         print ("line as read from file: ",tempwords)
>
>         for n in range(0, len(room)-1):
>             roomx[n] = tempwords[n]
>             #print(roomx[n])
>
>         print("roomx",roomx)
>         room[m] = roomx
>         print("room ",m,room[m])
>         print("current state of room array")
>         print("room 0",room[0])
>         print("room 1",room[1])
>         print("room 2",room[2])
>         print("room 3",room[3])
>         print("room 4",room[4])
>         print("room 5",room[5])
>         print("room 6",room[6])
>         print("room 7",room[7])
>
>         m += 1
>
>     textf.close()
>     return(room)
>
> #----END read_maze_data_file()
>
>
> #---------MAIN SECTION---------
>
> clearscreen()
>
>
> print("LOAD AN ARRARY FROM A FILE")
> print("              by Bill Allen")
> print()
> print("initial state of room array")
> print(room)
> print()
>
> print("data from file")
> room_final = read_maze_data_file()
> print("from MAIN")
> print(room_final)
> print()
>
> print("a PRINT_MAP call from MAIN")
> print_map()
> print()
> print()
>
>
> =======================
> partial sample output showing the current incorrect results:
> a PRINT_MAP call from MAIN
> +-------------+
> |MAP:   NSEWUD|
> |room1>  000050|
> |room2>  000050|
> |room3>  000050|
> |room4>  000050|
> |room5>  000050|
> |room6>  000050|
> |room7>  000050|
> +-------------+
> =========================
> the contents of the data file, mazegame.dat
> 0 0 0 0 0 0 0
> 0 0 4 2 0 0 0
> 0 0 0 1 3 6 0
> 0 0 5 0 2 0 0
> 0 1 0 5 0 0 0
> 0 3 0 0 4 0 7
> 0 0 0 0 0 0 2
> 0 0 0 0 0 5 0
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>    


-- 
Bob Gailer
919-636-4239
Chapel Hill NC