Re: [pygame] Name self not defined
Hi! __new__ returns a new instance of the class while __init__ is simply used to initialize instance variables. Normally you don't bother with __new__ unless you have a particular need (does not happen to often in my experience with Python), some types written in C may require it for deviating signatures of the constructor. Also, I try to make it a rule of thumb to place any superclass calls at the top of the __init__ method, this is useful to get a quick overview of what superclass init's are called, in particular if you have more than one. It's not possible or desirable in 100% of the cases, but I try to do it that way for better readability. Just my personal preference. /Peter On 2009-01-29 (Thu) 09:00, John Eikenberry wrote: > Jake b wrote: > > > On Tue, Jan 27, 2009 at 9:18 PM, Yanom Mobis wrote: > > > > > this is the code in question: > > > > > > class Car(Basicsprite): #car class > > >def __init__(self, speedarg=(0,0)): > > >self.speed = speedarg > > >Basicsprite.__init__(self) > > > > > > > Is this valid to call parent constructor after other statements? ( Think > > this is invalid in other languages -- just not sure about python ) > > Yes. You can call the parents __init__() anywhere in the overridden method. > But... __init__() is not the constructor in the traditional sense (as I > understand it), it is already passed the constructed instance. In python > the constructor is the __new__() method which is passed the class and you > must call the superclass' __new__() to get the instance to work with. > > -- > > John Eikenberry > [...@zhar.net - http://zhar.net] > [PGP public key @ http://zhar.net/jae_at_zhar_net.gpg] > __ > "Perfection is attained, not when no more can be added, but when no more can > be > removed." -- Antoine de Saint-Exupery
Re: [pygame] Name self not defined
Ian Mallett wrote: > Frankly, I like this solution: > self.rect = self.rect.move(speedv or (0,0)) > Looks Pythonic to me. +1 -- John Eikenberry [...@zhar.net - http://zhar.net] [PGP public key @ http://zhar.net/jae_at_zhar_net.gpg] __ "Perfection is attained, not when no more can be added, but when no more can be removed." -- Antoine de Saint-Exupery signature.asc Description: Digital signature
Re: [pygame] Name self not defined
Jake b wrote: > On Tue, Jan 27, 2009 at 9:18 PM, Yanom Mobis wrote: > > > this is the code in question: > > > > class Car(Basicsprite): #car class > >def __init__(self, speedarg=(0,0)): > >self.speed = speedarg > >Basicsprite.__init__(self) > > > > Is this valid to call parent constructor after other statements? ( Think > this is invalid in other languages -- just not sure about python ) Yes. You can call the parents __init__() anywhere in the overridden method. But... __init__() is not the constructor in the traditional sense (as I understand it), it is already passed the constructed instance. In python the constructor is the __new__() method which is passed the class and you must call the superclass' __new__() to get the instance to work with. -- John Eikenberry [...@zhar.net - http://zhar.net] [PGP public key @ http://zhar.net/jae_at_zhar_net.gpg] __ "Perfection is attained, not when no more can be added, but when no more can be removed." -- Antoine de Saint-Exupery signature.asc Description: Digital signature
Re: [pygame] Name self not defined
"or else", that's a good way of reading it, thanks. On Thu, Jan 29, 2009 at 1:27 AM, Bill Coderre wrote: > Interestingly, one rarely sees people use "and" as an idiom. It will execute > starting with the left-most statement, and keep going until one of them > fails, then stop, executing nothing further. So you could read it as "and > then" > Well, you often see things like: enemy = FindClosestEnemy() if enemy and enemy.can_attack(self): self.pair_off_with(enemy) else: self.flail_around_madly() ... though it isn't really the "and" idiom you're talking about. That would be more like: self.attacked_this_turn = enemy and self:attack(enemy) ... which is indeed rather rare (rightfully so) Emile
Re: [pygame] Name self not defined
On Tue, Jan 27, 2009 at 9:18 PM, Yanom Mobis wrote: > this is the code in question: > > class Car(Basicsprite): #car class >def __init__(self, speedarg=(0,0)): >self.speed = speedarg >Basicsprite.__init__(self) > Is this valid to call parent constructor after other statements? ( Think this is invalid in other languages -- just not sure about python ) -- Jake
Re: [pygame] Name self not defined
On Jan 28, 2009, at 4:06 PM, James Paige wrote: The "or" operator is what they call a "short circuiting" operator. If the first part is True then the second part is never evaluated. If the first part is False, then the second part is returned. Ah, the "or" idiom. Read it as "or else." I learned of this as a perl- ism of particular delight: open(FILE) or die "Can't open the file!"; perl also has inverted tests: die "The file is not there!" unless open(FILE); Not trying to start LANGUAGE WARS here, just pointing out that when the idioms line up with common natural-language idioms, it's peculiarly satisfying. Interestingly, one rarely sees people use "and" as an idiom. It will execute starting with the left-most statement, and keep going until one of them fails, then stop, executing nothing further. So you could read it as "and then"
Re: [pygame] Name self not defined
oh, thanks. --- On Tue, 1/27/09, James Paige wrote: From: James Paige Subject: Re: [pygame] Name self not defined To: pygame-users@seul.org Date: Tuesday, January 27, 2009, 9:24 PM -Inline Attachment Follows- On Tue, Jan 27, 2009 at 07:18:20PM -0800, Yanom Mobis wrote: > this is the code in question: > > class Car(Basicsprite): #car class > def __init__(self, speedarg=(0,0)): > self.speed = speedarg > Basicsprite.__init__(self) > def move(self, speedv=self.speed): > self.rect = self.rect.move(speedv) > > > however, when I try to import that class from python: > > > > >>> from basicsprite import Car > Traceback (most recent call last): > File "", line 1, in > File "basicsprite.py", line 14, in > class Car(Basicsprite): #car class > File "basicsprite.py", line 18, in Car > def move(self, speedv=self.speed): > NameError: name 'self' is not defined > > > > how can self not be defined?? You can't use "self" in the "def" line. Here is how I usually accomplish what you are trying to do: class Car(Basicsprite): #car class def __init__(self, speedarg=(0,0)): self.speed = speedarg Basicsprite.__init__(self) def move(self, speedv=None): if speedv==None: speedv = self.speedv self.rect = self.rect.move(speedv) But maybe somebody else can suggest a nicer way to do that. --- James Paige
Re: [pygame] Name self not defined
The "or" operator is what they call a "short circuiting" operator. If the first part is True then the second part is never evaluated. If the first part is False, then the second part is returned. --- James On Wed, Jan 28, 2009 at 04:03:27PM -0800, Yanom Mobis wrote: >how do you use the or statement in arguments? >i have never seen it done. > >--- On Wed, 1/28/09, Ian Mallett wrote: > > From: Ian Mallett > Subject: Re: [pygame] Name self not defined > To: pygame-users@seul.org > Date: Wednesday, January 28, 2009, 4:25 PM > > Frankly, I like this solution: > self.rect = self.rect.move(speedv or (0,0)) > Looks Pythonic to me.
Re: [pygame] Name self not defined
how do you use the or statement in arguments? i have never seen it done. --- On Wed, 1/28/09, Ian Mallett wrote: From: Ian Mallett Subject: Re: [pygame] Name self not defined To: pygame-users@seul.org Date: Wednesday, January 28, 2009, 4:25 PM Frankly, I like this solution: self.rect = self.rect.move(speedv or (0,0)) Looks Pythonic to me.
Re: [pygame] Name self not defined
Frankly, I like this solution: self.rect = self.rect.move(speedv or (0,0)) Looks Pythonic to me.
Re: [pygame] Name self not defined
Damn, still haven't learned to format after all these years: class Car(Basicsprite): #car class def move(self, speedv=None): self.rect = self.rect.move(speedv or (0,0))
Re: [pygame] Name self not defined
Marius Gedminas wrote: On Tue, Jan 27, 2009 at 07:24:13PM -0800, James Paige wrote: You can't use "self" in the "def" line. Here is how I usually accomplish what you are trying to do: class Car(Basicsprite): #car class def __init__(self, speedarg=(0,0)): self.speed = speedarg Basicsprite.__init__(self) def move(self, speedv=None): if speedv==None: speedv = self.speedv self.rect = self.rect.move(speedv) But maybe somebody else can suggest a nicer way to do that. The idiomatic way to express that is 'if speedv is None:'. See http://www.python.org/dev/peps/pep-0008/ Marius Gedminas Don't know how `idiomatic` or `pythonic` it is but I see a lot of people use `or` expressions: class Car(Basicsprite): #car class def move(self, speedv=None): self.rect = self.rect.move(speedv or (0,0)) no `speedv`, in (x,y) tuple format, is ever going to bool as False so if it `is None` it will use `self.speedv` of (0,0)
Re: [pygame] Name self not defined
Hey thanks for that link Marius :) For anyone who's interested, here's the suggestion he was referencing: "- Comparisons to singletons like None should always be done with 'is' or 'is not', never the equality operators." On Wed, Jan 28, 2009 at 6:15 AM, Marius Gedminas wrote: > On Tue, Jan 27, 2009 at 07:24:13PM -0800, James Paige wrote: > > You can't use "self" in the "def" line. Here is how I usually accomplish > > what you are trying to do: > > > > class Car(Basicsprite): #car class > > def __init__(self, speedarg=(0,0)): > > self.speed = speedarg > > Basicsprite.__init__(self) > > def move(self, speedv=None): > > if speedv==None: speedv = self.speedv > > self.rect = self.rect.move(speedv) > > > > > > But maybe somebody else can suggest a nicer way to do that. > > The idiomatic way to express that is 'if speedv is None:'. > See http://www.python.org/dev/peps/pep-0008/ > > Marius Gedminas > -- > lg_PC.gigacharset (lg = little green men language, PC = proxima centauri) >-- Markus Kuhn provides an example of a locale > > -BEGIN PGP SIGNATURE- > Version: GnuPG v1.4.9 (GNU/Linux) > > iD8DBQFJgGidkVdEXeem148RAkO0AJ9HCXWcvCbJeJxctMEoqVlTLXNRvQCgk1Oo > vW/kT4jEnhftgSWgEDPo5o0= > =Ijvy > -END PGP SIGNATURE- > >
Re: [pygame] Name self not defined
On Tue, Jan 27, 2009 at 07:24:13PM -0800, James Paige wrote: > You can't use "self" in the "def" line. Here is how I usually accomplish > what you are trying to do: > > class Car(Basicsprite): #car class > def __init__(self, speedarg=(0,0)): > self.speed = speedarg > Basicsprite.__init__(self) > def move(self, speedv=None): > if speedv==None: speedv = self.speedv > self.rect = self.rect.move(speedv) > > > But maybe somebody else can suggest a nicer way to do that. The idiomatic way to express that is 'if speedv is None:'. See http://www.python.org/dev/peps/pep-0008/ Marius Gedminas -- lg_PC.gigacharset (lg = little green men language, PC = proxima centauri) -- Markus Kuhn provides an example of a locale signature.asc Description: Digital signature
Re: [pygame] Name self not defined
On Wed, Jan 28, 2009 at 2:18 PM, Yanom Mobis wrote: > this is the code in question: > > class Car(Basicsprite): #car class >def __init__(self, speedarg=(0,0)): >self.speed = speedarg >Basicsprite.__init__(self) >def move(self, speedv=self.speed): >self.rect = self.rect.move(speedv) > > > however, when I try to import that class from python: > > > > >>> from basicsprite import Car > Traceback (most recent call last): > File "", line 1, in > File "basicsprite.py", line 14, in >class Car(Basicsprite): #car class > File "basicsprite.py", line 18, in Car >def move(self, speedv=self.speed): > NameError: name 'self' is not defined > > > > how can self not be defined?? > > > > This line contains your error. > def move(self, speedv=self.speed): At the time the default arguments are evaluated (at the time of function definition), self - your instance - is not defined. Try something along these lines instead: def move(self, speedv=None): if speedv is None: speedv = self.speed
Re: [pygame] Name self not defined
On Tue, Jan 27, 2009 at 07:18:20PM -0800, Yanom Mobis wrote: > this is the code in question: > > class Car(Basicsprite): #car class > def __init__(self, speedarg=(0,0)): > self.speed = speedarg > Basicsprite.__init__(self) > def move(self, speedv=self.speed): > self.rect = self.rect.move(speedv) > > > however, when I try to import that class from python: > > > > >>> from basicsprite import Car > Traceback (most recent call last): > File "", line 1, in > File "basicsprite.py", line 14, in > class Car(Basicsprite): #car class > File "basicsprite.py", line 18, in Car > def move(self, speedv=self.speed): > NameError: name 'self' is not defined > > > > how can self not be defined?? You can't use "self" in the "def" line. Here is how I usually accomplish what you are trying to do: class Car(Basicsprite): #car class def __init__(self, speedarg=(0,0)): self.speed = speedarg Basicsprite.__init__(self) def move(self, speedv=None): if speedv==None: speedv = self.speedv self.rect = self.rect.move(speedv) But maybe somebody else can suggest a nicer way to do that. --- James Paige
[pygame] Name self not defined
this is the code in question: class Car(Basicsprite): #car class def __init__(self, speedarg=(0,0)): self.speed = speedarg Basicsprite.__init__(self) def move(self, speedv=self.speed): self.rect = self.rect.move(speedv) however, when I try to import that class from python: >>> from basicsprite import Car Traceback (most recent call last): File "", line 1, in File "basicsprite.py", line 14, in class Car(Basicsprite): #car class File "basicsprite.py", line 18, in Car def move(self, speedv=self.speed): NameError: name 'self' is not defined how can self not be defined??
