我在Python shell上检查了一些示例,它们似乎吐出了相同的数字。 但是,在一个程序中,应该以大量数字为近似值,它们显然会产生不同的结果。

我正在尝试编写一个小程序来模拟对象在矩形平面上的运动。 为此,我必须编写一个名为“ RectangularRoom”的类,该类接受宽度和高度并创建网格:

class RectangularRoom(object):
"""
A RectangularRoom represents a rectangular region containing clean or dirty
tiles.

A room has a width and a height and contains (width * height) tiles. At any
particular time, each of these tiles is either clean or dirty.
"""
def __init__(self, width, height):
    """
    Initializes a rectangular room with the specified width and height.

    Initially, no tiles in the room have been cleaned.

    width: an integer > 0
    height: an integer > 0
    """
    self.width = width
    self.height = height
    self.room_coordinates = []
    for m in range(self.width):
        for n in range(self.height):
            self.room_coordinates.append((m,n))
    self.cleaned = []
def cleanTileAtPosition(self, pos):
    """
    Mark the tile under the position POS as cleaned.

    Assumes that POS represents a valid position inside this room.

    pos: a Position
    """
    self.cleaned.append((int(pos.getX()), int(pos.getY())))

def isTileCleaned(self, m, n):
    """
    Return True if the tile (m, n) has been cleaned.

    Assumes that (m, n) represents a valid tile inside the room.

    m: an integer
    n: an integer
    returns: True if (m, n) is cleaned, False otherwise
    """
    assert type (m)== int and type (n) == int
    return (m,n) in self.cleaned

def getNumTiles(self):
    """
    Return the total number of tiles in the room.

    returns: an integer
    """
    return self.width*self.height

def getNumCleanedTiles(self):
    """
    Return the total number of clean tiles in the room.

    returns: an integer
    """
    return len(self.cleaned)

def getRandomPosition(self):
    """ 
    Return a random position inside the room.

    returns: a Position object.
    """
    return Position (random.randrange(0 , self.width), random.randrange(0 , self.height))

def isPositionInRoom(self, pos):
    """
    Return True if pos is inside the room.

    pos: a Position object.
    returns: True if pos is in the room, False otherwise.
    """
    return (int(pos.getX()), int(pos.getY())) in self.room_coordinates

如您所见,我使用int()方法和随机生成器“ random.randrange”实现了它。

在解决方案中,教师已使用math.floor()函数和随机生成器random.random()实现了此类:

class RectangularRoom(object):
"""
A RectangularRoom represents a rectangular region containing clean or dirty
tiles.

A room has a width and a height and contains (width * height) tiles. At any
particular time, each of these tiles is either clean or dirty.
"""
def __init__(self, width, height):
    """
    Initializes a rectangular room with the specified width and height.

    Initially, no tiles in the room have been cleaned.

    width: an integer > 0
    height: an integer > 0
    """
    self.width = width
    self.height = height
    self.tiles = {}
    for x in range(self.width):
        for y in range(self.height):
            self.tiles[(x, y)] = False

def cleanTileAtPosition(self, pos):
    """
    Mark the tile under the position POS as cleaned.

    Assumes that POS represents a valid position inside this room.

    pos: a Position
    """
    x = math.floor(pos.getX())
    y = math.floor(pos.getY())
    self.tiles[(x, y)] = True

def isTileCleaned(self, m, n):
    """
    Return True if the tile (m, n) has been cleaned.

    Assumes that (m, n) represents a valid tile inside the room.

    m: an integer
    n: an integer
    returns: True if (m, n) is cleaned, False otherwise
    """
    return self.tiles[(m, n)]

def getNumTiles(self):
    """
    Return the total number of tiles in the room.

    returns: an integer
    """
    return self.width * self.height

def getNumCleanedTiles(self):
    """
    Return the total number of clean tiles in the room.

    returns: an integer
    """
    return sum(self.tiles.values())

def getRandomPosition(self):
    """
    Return a random position inside the room.

    returns: a Position object.
    """
    return Position(random.random() * self.width,
                    random.random() * self.height)

def isPositionInRoom(self, pos):
    """
    Return True if pos is inside the room.

    pos: a Position object.
    returns: True if pos is in the room, False otherwise.
    """
    return ((0 <= pos.getX() < self.width)
            and (0 <= pos.getY() < self.height))

令人惊讶的是,这两个代码块产生了完全不同的结果。 我想知道为什么会这样。 int()和floor()对正数应具有相同的作用,并且两个随机函数似乎产生相似的数。

===============>>#1 票数:5 已采纳

好吧,我不知道您问题的答案-我怀疑他们返回的是完全相同的东西。 但是,我认为您的解决方案存在一个问题,可能会解释输出:

在“ cleanTileAtPosition”中

self.cleaned.append((int(pos.getX()), int(pos.getY())))

在“ getNumCleanedTiles”中

return len(self.cleaned)

此代码似乎允许多次清洁图块。 这不是您的老师的代码,因为磁贴只能设置为“ True”一次。

(顺便说一下,由于random.randrange返回一个整数。.整数转换应该什么都不做!)

编辑:另外-我认为类型差异值得考虑。 但是您所有的类型都是“ ints”,所以这不是问题。

===============>>#2 票数:2

您的方法之间有一个很大的不同。 random.randrange返回一个整数,然后在位置上调用int() 您正在使用整数。 同时, random.random() * something返回浮点数,而math.floor也返回浮点数。 您的老师一直在使用浮子。

那至少是intmath.floor之间的区别,但是我不知道为什么会产生完全不同的结果。 您能对此具体一点吗?

===============>>#3 票数:1

考虑以下示例:

>>> a = 1.2
>>> b = int(a)
>>> c = math.floor(a)
>>> b
1
>>> c
1.0
>>> type(c)
<type 'float'>
>>> type(a)
<type 'float'>
>>> type(b)
<type 'int'>

即使int()和floor()对正整数做“相同的事情”,结果的类型也不同。 这可能会导致各种不同的交互,具体取决于您稍后对其进行的操作。 尽管Python不一定会为您提供所需的结果,但Python会从其角度探讨如何使其“起作用”。

通常,在进行编程中的任何数学运算时,您都希望使用的类型保持一致,这样就不必担心类型转换和升级以及所有令人讨厌的东西。

===============>>#4 票数:0

使用“ integers”而不是math.floor terhe会更好-仍然,Python在float <->整数比较中具有足够的黑魔法,因此单独的区别在上面的代码中应该没有问题。 但是,这两个版本中的代码都有独特的Java或C ++“重音”,比简单的Python代码复杂得多。 差异可能出现在代码的其他点上-不在此舍入中。 例如-首先尝试使用random.randint而不是获取float并对其进行四舍五入。

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