RE: Python: A Program I'd Love To Understand

  • From: "Homme, James" <james.homme@xxxxxxxxxxxx>
  • To: "programmingblind@xxxxxxxxxxxxx" <programmingblind@xxxxxxxxxxxxx>
  • Date: Wed, 22 Jun 2011 15:25:51 -0400

Hi Chris,
That was one of the things that confused me. I pasted the program from the web 
site, and it said map. Then I read about map.

Jim

From: programmingblind-bounce@xxxxxxxxxxxxx 
[mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of Q
Sent: Wednesday, June 22, 2011 3:10 PM
To: programmingblind@xxxxxxxxxxxxx
Subject: Re: Python: A Program I'd Love To Understand

each function returns the next key in the dictionary to call by the main loop. 
Presumably the last one exits or goes back to the beginning or something 
because otherwise the loop never exits.
Tip: call your argument something other than map, perhaps room_map or 
something, as map is a builtin function that you're shadowing.


On 6/22/2011 2:56 PM, Homme, James wrote:

Hi,

In the program in question, here is more code with more attempts to understand 
what's going on.



In the real program is a function call that is physically below the function 
that it calls.



Here's the function, and call, heavily commented in an attempt to understand 
what's going on. Please correct and elaborate if necessary.



def runner(map, start):

  # Loop through the dictionary and call each function.



  print "Top of runner function." # For understanding what's going on. Remove 
later

  # next will be the first function of the dictionary.

  next = start

  # I think that the condition will be False once we have no more functions to 
loop through.

  while True:

    print "Top of loop: next is now %s." % next # Remove later.

    room = map[next] # Get the name of the function we are going to call 
further down.

    print "Room is now %s." % room # Remove later.

    print "\n--------"

    next = room() # Call the function and get back what it returns.

    print "Bottom of loop: next is now %s." % next



# Call runner. Give it the dictionary, and which key to start with.

runner(ROOMS, 'princess_lives_here')



Thanks.



Jim



From: 
programmingblind-bounce@xxxxxxxxxxxxx<mailto:programmingblind-bounce@xxxxxxxxxxxxx>
 [mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of Q
Sent: Wednesday, June 22, 2011 2:04 PM
To: programmingblind@xxxxxxxxxxxxx<mailto:programmingblind@xxxxxxxxxxxxx>
Subject: Re: Python: A Program I'd Love To Understand



Jim,
Those functions are defined elsewhere in the module, right?
Python supports a computer science concept known as first-class functions:
http://en.wikipedia.org/wiki/First-class_function
If you don't understand, feel free to poke me and I'll explain further.

On 6/22/2011 1:59 PM, Homme, James wrote:

Hi,

I have lots of questions about the current Python exercise I'm working on, so 
I'll just ask one at a time. Hope you have lots of patience.



First question. I think I should be getting a compiler error but I'm not. I 
thought I had to put some sort of quotes around this code after the commas. Why 
is this compiling OK?



ROOMS = { 'death': death,

  'princess_lives_here': princess_lives_here,

  'gold_koi_pond': gold_koi_pond,

  'big_iron_gate': big_iron_gate,

  'bear_with_sword': bear_with_sword

  }



Thanks.



Jim



Jim Homme,

Usability Services,

Phone: 412-544-1810.



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