I have checked a few examples on the Python shell and they seem to spit out same numbers. But in a program where large set of numbers are supposed to be approximated, they apparently produce different results.
I am trying to write a little program that simulates movement of an object on a rectangular plane. For that, I had to write a class named "RectangularRoom" that takes in a width and a height and creates a grid:
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
As you see I implemented it using the int() method and the random generator "random.randrange".
In the solution, the teacher has implemented this class using the math.floor() function and the random generator random.random():
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))
Surprisingly, these two chunks of code produce completely different results. I want to know why this happens. int() and floor() should have the same effect on a positive number and the two random functions seem to produce similar numbers.