代码疑问：clean/count函数未按指定Endpoint执行，需实现重复交互

1. 限定操作范围（核心修改） #

要让clean和count仅处理从行0到endRow、列0到endColumn的区域，只需将遍历范围从整个SIZE改为endRow+1和endColumn+1（Python的range是左闭右开区间，加1才能包含指定的行/列）。

修改后的clean函数： #

def clean(world, endRow, endColumn):
    print("Scooping the poop")
    # 仅遍历0到endRow的行、0到endColumn的列
    for r in range(endRow + 1):
        for c in range(endColumn + 1):
            if world[r][c] == POOP:
                world[r][c] = CLEANED

修改后的count函数： #

def count(world, endRow, endColumn):
    print("Counting number of occurances of a character")
    number = 0
    element = input("Enter character: ")
    # 仅遍历指定范围内的区域
    for r in range(endRow + 1):
        for c in range(endColumn + 1):
            if world[r][c] == element:
                number += 1 
    return(element, number)

2. 实现重复交互逻辑 #

在start函数中加入循环，每次完成统计和清理后，询问用户是否继续操作，输入q即可退出。

修改后的start函数： #

def start():
    world = createWorld()
    display(world)
    while True:
        endRow, endColumn = getEndPoint()
        element, number = count(world, endRow, endColumn)
        print("# occurances of %s=%d" % (element, number))
        clean(world, endRow, endColumn)    
        display(world)
        # 询问是否继续操作
        choice = input("Enter 'q' to quit, or any other key to continue: ")
        if choice.lower() == 'q':
            break
start()

3. 修复遗漏的模块导入 #

原代码中createElement使用了random模块但未导入，需在代码开头添加：

import random

完整修改后的代码 #

import random

SIZE = 4
EMPTY = " "
PERSON = "P"
PET = "T"
POOP = "O"
ERROR = "!"
CLEANED = "."
MAX_RANDOM = 10

def clean(world,endRow,endColumn):
    print("Scooping the poop")
    for r in range(endRow + 1):
        for c in range(endColumn + 1):
            if world[r][c] == POOP:
                world[r][c] = CLEANED
            
                    
# @args(reference to a alist of characters,integer,integer)
# Function will count the number of occurences of the character specified by the user up the specified
# end point (row/column specified by the user).
# @return(character,integer)
def count(world,endRow,endColumn):
    print("Counting number of occurances of a character")
    number = 0
    element = input("Enter character: ")
    for r in range(endRow + 1):
        for c in range(endColumn + 1):
            if world[r][c] == element:
                number += 1 
    return(element,number)

# Randomly generates an 'occupant' for a location in the world
# @args(none)
# Randomly generates and returns a character according to the specified probabilities.
#  *50% probability empty space
#  *20% probability of a person
#  *10% probability of a pet
#  *20% probability of fecal matter
# @return(character)
def createElement():
    tempNum = random.randrange(MAX_RANDOM)+1

    # 50% chance empty
    if ((tempNum >= 1) and (tempNum <= 5)):
        tempElement = EMPTY 

    # 20% of a person
    elif ((tempNum >= 6) and (tempNum <= 7)):
        tempElement = PERSON

    # 10% chance of pet
    elif (tempNum == 8):
        tempElement = PET

    # 20% chance of poop in that location (lots in this world)
    elif ((tempNum >= 9) and (tempNum <= 10)):
        tempElement = POOP

    # In case there's a bug in the random number genrator
    else:
        tempElement = ERROR

    return(tempElement)

# Creates the SIZExSIZE world. Randomly populates it with the 
# return values from function createElement
# @args(none)
# Randomly populates the 2D list which is returned to the caller.
# @return(reference to a list of characters)
def createWorld():
    world = [] #  Create a variable that refers to a 1D list. 
    r = 0

    #  Outer 'r' loop traverses the rows. 
    # Each iteration of the outer loop creates a new 1D list.
    while (r < SIZE):
        tempRow = []  
        world.append(tempRow)  # Create new empty row
        c = 0
        # The inner 'c' loop traverses the columns of the newly 
        # created 1D list creating and initializing each element
        # to the value returned by createElement()
        while (c < SIZE):
            element = createElement()
            tempRow.append(element)
            c = c + 1
        r = r + 1    
    return(world)

# Shows the elements of the world. All the elements in a row will
# appear on the same line.
# @args(reference to a list of characters)
# Displays the 2D list with each row on a separate line.
# @return(nothing)
def display(world):
    print("OUR WORLD")
    print("========")
    r = 0
    while (r < SIZE): # Each iteration accesses a single row 
        c = 0
        while (c < SIZE):  # Each iteration accesses an element in a row
            print(world[r][c], end="")
            c = c + 1
        print()  # Done displaying row, move output to the next line
        r = r + 1 

# @args(none)
# @return(integer,integer)
def getEndPoint():
    endRow = int(input("Enter the row (0-3): "))
    while not 0 <= endRow <= 3:
        print("Invalid input. Value must be in range 0-3")
        endRow = int(input("Enter the row: "))
    endColumn = int(input("Enter the column (0-3): "))
    while not 0 <= endColumn <= 3:
        print("Invalid input. Value must be in range 0-3")
        endColumn = int(input("Enter the column: "))
    return(endRow,endColumn)

# Starting execution point for the program.
def start():
    world = createWorld()
    display(world)
    while True:
        endRow, endColumn = getEndPoint()
        element, number = count(world, endRow, endColumn)
        print("# occurances of %s=%d" % (element, number))
        clean(world, endRow, endColumn)    
        display(world)
        choice = input("Enter 'q' to quit, or any other key to continue: ")
        if choice.lower() == 'q':
            break
start()

内容的提问来源于stack exchange，提问作者anonymous