Re: [Tutor] Questions about classes
Hi,
Was hoping someone could help me.
I have downloaded the latest pygame 1.9.1 i think) to a Mac powerbook OS
10.4.11.
Python 3 does not recognise pygame although python 2.7 version does
(unfortunately have never programmed python 2.7 and don't no how).
Any help would be much appreciated.
Thanks
Ciaran
On 13 Nov 2012, at 12:57, Steven D'Aprano wrote:
> On 13/11/12 13:49, brandon w wrote:
>
>
>> 1. I saw in the book an assignment written like this:
>>
>> class HumanBeing:
>> def makeName(self, name):
>> *self.name = name*
>> *
>> *
>> Why is it not written like this?:
>>
>> class HumanBeing:
>> def makeName(self, name):
>> * name = self.name*
>
> This creates a class called "HumanBeing". It includes a method called
> "makeName". Methods are very similar to functions, the differences will
> become clear further on.
>
> Methods are defined in the same way as functions: the "def" keyword,
> followed by the name of method, then the parameters. Each parameter
> creates a local variable, so the "makeName" method has two local
> variables:
>
> - self
> - name
>
> "self" is special. When you call the method, Python will automatically
> provide the "self" argument. So if you do this:
>
> fred = HumanBeing() # create an instance of HumanBeing class
> fred.makeName("flintstone")
>
> the makeName method gets passed two arguments:
>
> - self = fred, provided automatically by Python
> - name = "flintstone", provided by you
>
>
> Now, inside the body of the method, we have this:
>
> self.name = name
>
> That says:
>
> - take the argument *name* (which has value "flintstone")
> - attach it to the instance *self* using the attribute called "name"
>
> After the line finishes executing, the instance *fred* will now have
> an attribute *name* with value "flintstone".
>
> So if you later call:
>
> print(fred.name)
>
> Python will print "flintstone".
>
> What if it were written the other way, as you suggested?
>
> name = self.name
>
> That goes in the opposite direction: first Python tries to look up
> an attribute called name. It probably doesn't find one, and so it
> will raise an exception and print an error message. But let's
> suppose it did find one. It then takes that value and stores it
> in the local variable "name", over-writing the local variable you
> provided as an argument to the method.
>
> Then, when the method returns (either at a "return" statement, or
> by reaching the end of the method), the local variable is
> forgotten and no permanent change is made.
>
>
>
>> 2. Why use a class in the first place? What is the purpose of constructing
>> a class instead of just writing a program with a bunch of functions?
>
> Classes are useful for a couple of reasons:
>
> 1) Encapsulation
>
> A class keeps together related code and data. A good example comes from the
> Python built-in class "list". The list class combines:
>
> - a storage area for the list data;
> - methods which operate on that list data.
>
> For example, lists have a method "index". But strings also have a method
> called "index". The list.index method knows how to search a list. It knows
> nothing about strings, and doesn't need to care about strings. It only
> needs to care about lists. The str.list method knows how to search a string.
> It knows nothing about lists, and only cares about strings. That makes it
> much easier to program. Instead of one giant function:
>
>
> def index(obj, value):
>if obj is a string:
>code for searching strings
>elif obj is a list:
>code for searching lists
>elif obj is a tuple:
>code for searching tuples
>else:
>raise TypeError("don't know how to index obj")
>
> instead each branch of the function gets encapsulated into a str class, a
> list class, a tuple class, and anything else that you might want to index.
> If you write a Book class, you can give it an index method without needing
> to care about lists, strings, tuples, etc.
>
>
> The other advantage of classes is:
>
> 2) Inheritance
>
> With classes, you can *inherit* behaviour by creating a subclass. Say, for
> example, you want a type of list that is exactly the same as ordinary lists
> except that every time you append a value, it prints what you appended. This
> might be useful for debugging. Without inheritance, you would have to
> duplicate the entire code base for list, many hundreds or thousands of lines
> of code. But with inheritance, it just takes FOUR lines:
>
> class MyList(list):
>def append(self, value):
>print("appending %s" % value)
>super(MyList, self).append(value)
>
>
> This creates a new class called "MyList", which inherits from the built-in
> list class; everything else is the same as list, except for the append
> method, which prints the value first, then calls the built-in list.append
> method.
>
> (If the super() call looks a bit mysterious, don't worry too much abou
[Tutor] Pygame problem with mac
Hi, Was hoping u could help me. I can't seem to download a version of pygame that is compatible with python 3.2 on my Mac powerbook with OS tiger. I only seem to he able to get pygame for python 2.7 which i have never used. Thanks Ciaran ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] invalid literal for int error in Game loop
HI All,
Was hoping someone could help me with a problem I am having programming a game
using pygame.
I am trying to return a variable with a integer value defined by user input
from a function.
Basically the idea is to allow the player to select the level of difficulty by
selecting from a choice of keys, each key corresponding too the number of
frames per second. The function code is as follows:
def difficultyLevel():
FPS = ''
windowSurface = pygame.display.set_mode((WINDOWWIDTH,
WINDOWHEIGHT),pygame.FULLSCREEN)
windowSurface.fill(BACKGROUNDCOLOUR)
drawText('LEVEL OF PLAY', font3, windowSurface, (WINDOWWIDTH/6),
(WINDOWHEIGHT/6))
drawText('B: Your an absoulute Begineer', font3, windowSurface,
(WINDOWWIDTH/6)-100, (WINDOWHEIGHT/6)+100)
drawText('M: Not Too Snazy', font3, windowSurface, (WINDOWWIDTH/6)-100,
(WINDOWHEIGHT/6)+150)
drawText('H: Deathwish' ,font3,windowSurface, (WINDOWWIDTH/6)-100,
(WINDOWHEIGHT/6)+200)
pygame.display.update()
for event in pygame.event.get():
if event.type == QUIT:
terminate()
if event.type == KEYDOWN:
if event.key == ord('b'):
FPS = 30
elif event.key == ord('m'):
FPS = 70
elif event.key == ord('h'):
FPS = 120
return FPS
The function is then called and FPS converted too a integer value in the main
game loop as follows:
topScore = 0
while True:
#set up the game and all intial key and mouse movement values as false
baddies = [] #baddies as a empy list
score = 0
etc
FPS = int(difficultyLevel())
FPS is then used within the game loop to allow for number of frames per second
in:
mainClock.tick(FPS)
However I keep getting the following error:
ValueError: invalid literal for int() with base 10: ''
Please note I am a absolute beoingeer in programming and have had no formal
education to date so please excuse anything I may of left out !!
Thanks
Ciaran
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Re: [Tutor] invalid literal for int error in Game loop
Thanks for the feedback.
Steve, If I set the FPS to a default of say 30, the game seems to run at this
default FPS=30 regardless of the key pressed in the function.
Dave, If I remove the the default value at the start of the function and add it
to elif in the loop I get the following error:
Traceback (most recent call last):
File "/Users/callanmooneys/Desktop/Pythoin Programmes/Aliens Game/dodger ver
3 instructons.py", line 139, in
FPS = difficultyLevel()
File "/Users/callanmooneys/Desktop/Pythoin Programmes/Aliens Game/dodger ver
3 instructons.py", line 50, in difficultyLevel
return FPS
UnboundLocalError: local variable 'FPS' referenced before assignment
I wondered if i could set FPS to nether a string or integer and just declare it
by setting FPS=None but I get the following error:
Traceback (most recent call last):
File "/Users/callanmooneys/Desktop/Pythoin Programmes/Aliens Game/dodger ver
3 instructons.py", line 301, in
mainClock.tick(FPS)
TypeError: a float is required
Cheers
Ciaran
On 20 Dec 2012, at 21:07, Dave Angel wrote:
> On 12/20/2012 03:51 PM, Steven D'Aprano wrote:
>> On 21/12/12 07:40, Ciaran Mooney wrote:
>>
>>> def difficultyLevel():
>>> FPS = ''
>>
>> Here you set the variable FPS to the empty string.
>>
>>> if event.type == KEYDOWN:
>>> if event.key == ord('b'):
>>> FPS = 30
>>> elif event.key == ord('m'):
>>> FPS = 70
>>> elif event.key == ord('h'):
>>> FPS = 120
>>
>> These three options set FPS to an integer value. But notice that if
>> the user
>> does not press one of the b m or h keys, FPS never gets changed so it
>> still
>> has the initial value of the empty string.
>>
>>> return FPS
>>>
>>> The function is then called and FPS converted too a integer value in
>>> the main game loop as follows:
>>
>>> FPS = int(difficultyLevel())
>>
>>> However I keep getting the following error:
>>>
>>> ValueError: invalid literal for int() with base 10: ''
>>
>> There are three possible values that difficultyLevel() may return:
>>
>> * if the user hits the 'h' key, it returns the integer value 120;
>> * if the user hits the 'm' key, it returns the integer value 70;
>> * if the user hits the 'b' key, it returns the integer value 30;
>> * otherwise, it returns the empty string.
>>
>> Three of the four values are already ints and don't need to be converted;
>> the fourth cannot be converted because it is not a numeric string.
>>
>> To fix this, change the line FPS = '' to a default integer value,
>> say, FPS = 30.
>>
>>
>>
>
> Or even better, remove that default value and add an else clause to the
> if/elif/elif section. That way it's all in one place, and it's more
> obvious that the return value will always be an int.
>
> And of course you can remove the int() call on the line
>FPS = int( difficultyLevel() )
> becomes
>FPS = difficultyLevel()
>
> BTW, when quoting an error, please include the whole traceback, not just
> one line of it. Here it was obvious, but many times other parts will be
> very useful, or even essential.
>
>
>
> --
>
> DaveA
>
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Re: [Tutor] invalid literal for int error in Game loop
On 4 Jan 2013, at 19:20, Francesco Loffredo wrote:
> Ciaran Mooney wrote:
>> Thanks for the feedback.
>>
>> Steve, If I set the FPS to a default of say 30, the game seems to run at
>> this default FPS=30 regardless of the key pressed in the function.
>>
>> Dave, If I remove the the default value at the start of the function and add
>> it to elif in the loop I get the following error:
>>
>>
>> Traceback (most recent call last):
>> File "/Users/callanmooneys/Desktop/Pythoin Programmes/Aliens Game/dodger
>> ver 3 instructons.py", line 139, in
>> FPS = difficultyLevel()
>> File "/Users/callanmooneys/Desktop/Pythoin Programmes/Aliens Game/dodger
>> ver 3 instructons.py", line 50, in difficultyLevel
>> return FPS
>> UnboundLocalError: local variable 'FPS' referenced before assignment
>>
>>
>> I wondered if i could set FPS to nether a string or integer and just declare
>> it by setting FPS=None but I get the following error:
>>
>> Traceback (most recent call last):
>> File "/Users/callanmooneys/Desktop/Pythoin Programmes/Aliens Game/dodger
>> ver 3 instructons.py", line 301, in
>> mainClock.tick(FPS)
>> TypeError: a float is required
>>
>> Cheers
>> Ciaran
> As far as I understood your problem, it seems that you need the difficulty
> level to be changed at the player's will during the game. In this case, the
> function gets called many times, maybe at every game loop. If this is true,
> you need a global FPS value to be changed by the player's choice, not one
> that you create inside the function.
>
> Try this:
>
> # put the line below out of the function definition and out of the game loop,
> usually together with other default program settings
> FPS = 30 # you want the game to be beginner-friendly, don't you?
>
> def difficultyLevel():
>global FPS
> windowSurface = pygame.display.set_mode((WINDOWWIDTH,
> WINDOWHEIGHT),pygame.FULLSCREEN)
> windowSurface.fill(BACKGROUNDCOLOUR)
> drawText('LEVEL OF PLAY', font3, windowSurface, (WINDOWWIDTH/6),
> (WINDOWHEIGHT/6))
> drawText('B: Your an absoulute Begineer', font3, windowSurface,
> (WINDOWWIDTH/6)-100, (WINDOWHEIGHT/6)+100)
> drawText('M: Not Too Snazy', font3, windowSurface, (WINDOWWIDTH/6)-100,
> (WINDOWHEIGHT/6)+150)
> drawText('H: Deathwish' ,font3,windowSurface, (WINDOWWIDTH/6)-100,
> (WINDOWHEIGHT/6)+200)
> pygame.display.update()
>
> for event in pygame.event.get():
> if event.type == QUIT:
> terminate()
>
> if event.type == KEYDOWN:
> if event.key == ord('b'):
> FPS = 30
> elif event.key == ord('m'):
> FPS = 70
> elif event.key == ord('h'):
> FPS = 120
>
> return FPS
>
> ... then let us know.
> Hope that helps
>
> Francesco
Thanks Francesco,
Ill give it a go and come back to u.
Ciaran
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Re: [Tutor] Beginner question
On 10 Aug 2013, at 04:30, eschneide...@comcast.net wrote:
> I've been learning python from the website 'inventwithpython.com', and I'm on
> a chapter that covers the following code:
>
> import random
> import time
> def displayIntro():
> print('You are in a land full of dragons. In front of you,')
> print('you see two caves. In one cave, the dragon is friendly')
> print('and will share his treasure with you. The other dragon')
> print('is greedy and hungry, and will eat you on sight.')
> print()
> def chooseCave():
> cave = ''
> while cave != '1' and cave != '2':
> print('Which cave will you go into? (1 or 2)')
> cave = input()
> return cave
> def checkCave(chosenCave):
> print('You approach the cave...')
> time.sleep(2)
> print('It is dark and spooky...')
> time.sleep(2)
> print('A large dragon jumps out in front of you! He opens his jaws
> and...')
> print()
> time.sleep(2)
> friendlyCave = random.randint(1, 2)
> if chosenCave == str(friendlyCave):
> print('Gives you his treasure!')
> else:
> print('Gobbles you down in one bite!')
> playAgain = 'yes'
> while playAgain == 'yes' or playAgain == 'y':
> displayIntro()
> caveNumber = chooseCave()
> checkCave(caveNumber)
> print('Do you want to play again? (yes or no)')
> playAgain = input()
>
> I'm confused about what the line 'checkCave(caveNumber)' does and how it
> works. I would appreciate any help with this
>
> Thank you,
>
> Eric
>
Hi Eric,
This line calls the method 'checkCave()'. This method takes the argument
caveNumber (checkCave(caveNumber) , which is a string returned from user input
generated in the method chooseCave().
In checkCave method, the value (caveNumber) is then used in a if/else statement
to compare with a random integer (parsed to a string str(frindlyCave)) to
determine whether you will be eaten or given treasure ;)
Hope that was of some help.
Ciaran
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