Re: [Tutor] FW: Can this be done easly
> From: andreeng...@gmail.com > Date: Sun, 19 Sep 2010 20:54:01 +0200 > Subject: Re: [Tutor] FW: Can this be done easly > To: rwob...@hotmail.com > CC: tutor@python.org > > On Sun, Sep 19, 2010 at 8:33 PM, Roelof Wobben wrote: > >> Hello, >> >> I changed the programm to this : >> >> import unittest >> class Point: >> def __init__(self, x=0, y=0): >> self.x = x >> self.y = y >> >> class Rectangle(object): >> def __init__(self, base_point, width=0, length=0): >> self.base_point = base_point >> self.width = width >> self.length = length >> >> def moverect(roelof, dx, dy): >> roelof.base_point.y += dy >> roelof.base_point.x +=dx >> return roelof >> >> r = Rectangle(Point(3, 4), 20, 30) >> moverect(r, 10, 11) >> assert r.base_point.x == 13, "wrong x position %d" % r.base_point.x >> assert r.base_point.y == 15, "wrong y position %d" % r.base_point.y >> >> But no output at all > > Which output had you expected, and why? > > > -- > André Engels, andreeng...@gmail.com Hello, Oke, I see it now. There is only output when it's not right. Roelof ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] FW: Can this be done easly
On Sun, Sep 19, 2010 at 8:33 PM, Roelof Wobben wrote: > Hello, > > I changed the programm to this : > > import unittest > class Point: > def __init__(self, x=0, y=0): > self.x = x > self.y = y > > class Rectangle(object): > def __init__(self, base_point, width=0, length=0): > self.base_point = base_point > self.width = width > self.length = length > > def moverect(roelof, dx, dy): > roelof.base_point.y += dy > roelof.base_point.x +=dx > return roelof > > r = Rectangle(Point(3, 4), 20, 30) > moverect(r, 10, 11) > assert r.base_point.x == 13, "wrong x position %d" % r.base_point.x > assert r.base_point.y == 15, "wrong y position %d" % r.base_point.y > > But no output at all Which output had you expected, and why? -- André Engels, andreeng...@gmail.com ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] FW: Can this be done easly
> To: tutor@python.org > From: __pete...@web.de > Date: Sun, 19 Sep 2010 20:07:05 +0200 > Subject: Re: [Tutor] FW: Can this be done easly > > Roelof Wobben wrote: > >> For this exercise : >> >> 3.Write a function named move_rect that takes a Rectangle and two >> parameters named dx and dy. It should change the location of the rectangle >> by adding dx to the x coordinate of corner and adding dy to the y >> coordinate of corner. >> >> Is this one of the possible solutions : >> >> class Point: >> def __init__(self, x=0, y=0): >> self.x = x >> self.y = y >> >> class Rectangle(object): >> def __init__(self, base_point, width=0, length=0): >> self.base_point = base_point >> self.width = width >> self.length = length >> >> def moverect(rectangle, dx, dy): >> rechthoek.base_point.y += dy >> rechthoek.base_point.x +=dx >> return rechthoek >> >> punt = Point(3,4) >> rechthoek = Rectangle (punt,20,30) >> test = moverect (Rectangle, 4,3) >> print rechthoek.base_point.x > > At first glance I'd say so. At second glance I see that you pass the class > and not an instance to the moverect() routine. Your program only seems to > work because you are not using the parameter rectangle but the global > rechthoek variable and as soon as you are trying to move rectangles with a > different variable name everything will break. > If I were to run your program I might even find more errors or problematic > behaviours. > > In the long run it's not a sustainable model to verify the correctness of > your programs by asking someone on the internet who is just as likely to be > wrong as you or might even fool you. > > Instead add some tests. For example, you could precalculate the expected > position and then check if the new position meets your expectation: > > r = Rectangle(Point(3, 4), 20, 30) > > moverect(r, 10, 11) > > if r.base_point.x == 13 and r.base_point.y == 15: > print "looks good" > else: > print "needs work" > > Because tests are needed very often there are libraries accompanying the > interpreter (unittest, doctest) to formalize them and for simple runtime > checks there is the assert statement. Instead of the if...else you could > write > > assert r.base_point.x == 13, "wrong x position %d" % r.base_point.x > assert r.base_point.y == 15, "wrong y position %d" % r.base_point.y > > Peter > > ___ > Tutor maillist - Tutor@python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor Hello, I changed the programm to this : import unittest class Point: def __init__(self, x=0, y=0): self.x = x self.y = y class Rectangle(object): def __init__(self, base_point, width=0, length=0): self.base_point = base_point self.width = width self.length = length def moverect(roelof, dx, dy): roelof.base_point.y += dy roelof.base_point.x +=dx return roelof r = Rectangle(Point(3, 4), 20, 30) moverect(r, 10, 11) assert r.base_point.x == 13, "wrong x position %d" % r.base_point.x assert r.base_point.y == 15, "wrong y position %d" % r.base_point.y But no output at all Roelof ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] FW: Can this be done easly
On Sun, Sep 19, 2010 at 7:02 PM, Roelof Wobben wrote: > > > > >> From: rwob...@hotmail.com >> To: __pete...@web.de >> Subject: RE: [Tutor] Can this be done easly >> Date: Sun, 19 Sep 2010 17:01:22 + >> >> >> >> >> >>> To: tutor@python.org >>> From: __pete...@web.de >>> Date: Sun, 19 Sep 2010 18:27:54 +0200 >>> Subject: Re: [Tutor] Can this be done easly >>> >>> Roelof Wobben wrote: >>> > Hint: why does this work: > >> def __init__(self, x=0, y=0): > > ...while this doesnt: > >> def _init_(self, base_point, width=0, length=0): > > Peter >>> Maybe because base_point has no value ? >>> >>> No. One __init__ has two underscores (correct) on each side, the other >>> _init_ only one (wrong). >>> >>> ___ >>> Tutor maillist - Tutor@python.org >>> To unsubscribe or change subscription options: >>> http://mail.python.org/mailman/listinfo/tutor >> >> > > Hello, > > Everybody thanks. > > For this exercise : > > 3.Write a function named move_rect that takes a Rectangle and two parameters > named dx and dy. It should change the location of the rectangle by adding dx > to the x coordinate of corner and adding dy to the y coordinate of corner. > > Is this one of the possible solutions : > > > class Point: > def __init__(self, x=0, y=0): > self.x = x > self.y = y > > class Rectangle(object): > def __init__(self, base_point, width=0, length=0): > self.base_point = base_point > self.width = width > self.length = length > > def moverect(rectangle, dx, dy): > rechthoek.base_point.y += dy > rechthoek.base_point.x +=dx > return rechthoek > > punt = Point(3,4) > rechthoek = Rectangle (punt,20,30) > test = moverect (Rectangle, 4,3) > print rechthoek.base_point.x This test happens to work, but your program is incorrect. In moverect, you should work with the local variable (rectangle), not with the global one (rechthoek), because it should be possible to call it for any Rectangle, not just with the Rectangle that happens to be called rechthoek. Then, when you call it, you should specify the Rectangle that you call it for, so test = moverect (Rectangle, 4, 3) should be test = moverect(rechthoek, 4, 3) Furthermore, you do not use test (which will be null anyway), so you can shorten this to moverect(rechthoek, 4, 3) -- André Engels, andreeng...@gmail.com ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] FW: Can this be done easly
Roelof Wobben wrote: > For this exercise : > > 3.Write a function named move_rect that takes a Rectangle and two > parameters named dx and dy. It should change the location of the rectangle > by adding dx to the x coordinate of corner and adding dy to the y > coordinate of corner. > > Is this one of the possible solutions : > > class Point: > def __init__(self, x=0, y=0): > self.x = x > self.y = y > > class Rectangle(object): > def __init__(self, base_point, width=0, length=0): > self.base_point = base_point > self.width = width > self.length = length > > def moverect(rectangle, dx, dy): > rechthoek.base_point.y += dy > rechthoek.base_point.x +=dx > return rechthoek > > punt = Point(3,4) > rechthoek = Rectangle (punt,20,30) > test = moverect (Rectangle, 4,3) > print rechthoek.base_point.x At first glance I'd say so. At second glance I see that you pass the class and not an instance to the moverect() routine. Your program only seems to work because you are not using the parameter rectangle but the global rechthoek variable and as soon as you are trying to move rectangles with a different variable name everything will break. If I were to run your program I might even find more errors or problematic behaviours. In the long run it's not a sustainable model to verify the correctness of your programs by asking someone on the internet who is just as likely to be wrong as you or might even fool you. Instead add some tests. For example, you could precalculate the expected position and then check if the new position meets your expectation: r = Rectangle(Point(3, 4), 20, 30) moverect(r, 10, 11) if r.base_point.x == 13 and r.base_point.y == 15: print "looks good" else: print "needs work" Because tests are needed very often there are libraries accompanying the interpreter (unittest, doctest) to formalize them and for simple runtime checks there is the assert statement. Instead of the if...else you could write assert r.base_point.x == 13, "wrong x position %d" % r.base_point.x assert r.base_point.y == 15, "wrong y position %d" % r.base_point.y Peter ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
[Tutor] FW: Can this be done easly
> From: rwob...@hotmail.com > To: __pete...@web.de > Subject: RE: [Tutor] Can this be done easly > Date: Sun, 19 Sep 2010 17:01:22 + > > > > > >> To: tutor@python.org >> From: __pete...@web.de >> Date: Sun, 19 Sep 2010 18:27:54 +0200 >> Subject: Re: [Tutor] Can this be done easly >> >> Roelof Wobben wrote: >> Hint: why does this work: > def __init__(self, x=0, y=0): ...while this doesnt: > def _init_(self, base_point, width=0, length=0): Peter >> >>> Maybe because base_point has no value ? >> >> No. One __init__ has two underscores (correct) on each side, the other >> _init_ only one (wrong). >> >> ___ >> Tutor maillist - Tutor@python.org >> To unsubscribe or change subscription options: >> http://mail.python.org/mailman/listinfo/tutor > > Hello, Everybody thanks. For this exercise : 3.Write a function named move_rect that takes a Rectangle and two parameters named dx and dy. It should change the location of the rectangle by adding dx to the x coordinate of corner and adding dy to the y coordinate of corner. Is this one of the possible solutions : class Point: def __init__(self, x=0, y=0): self.x = x self.y = y class Rectangle(object): def __init__(self, base_point, width=0, length=0): self.base_point = base_point self.width = width self.length = length def moverect(rectangle, dx, dy): rechthoek.base_point.y += dy rechthoek.base_point.x +=dx return rechthoek punt = Point(3,4) rechthoek = Rectangle (punt,20,30) test = moverect (Rectangle, 4,3) print rechthoek.base_point.x Roelof ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
