称重一袋钱

Question

我编制了一个程序来称重一袋钱，并计算出袋子里是否有太多/小硬币，以及两者之间的差别。

bagWeight = 0
totalCoinsAdd = 0
totalCoinsRemoved = 0
totalBagsChecked = 0

def inputs():    
    global bagWeight
    global totalCoinsAdd
    global totalCoinsRemoved 
    #The above grabs the global variables for use in the function    
    bagWeight = int(input("How much does the bag weigh? "))    
    denomination = ""
    denom = ['0.01', '0.02', '0.05', '0.10', '0.20', '0.50', '1', '2']
    while denomination not in denom:
        denomination = input("What denomination is the money? £")

    idealWeight = {    '2' : 120,    '1' : 190,    '0.50' : 160,    '0.20' : 250,   '0.10' : 325,    '0.05' : 325,   '0.02' : 356,    '0.01' : 356,    }
    #This dictionary stores the ideal weight of each bag.
    bagCoins = {    '2' : 10,    '1' : 20,    '0.50' : 20,    '0.20' : 50,   '0.10' : 50,    '0.05' : 100,   '0.02' : 50,    '0.01' : 100,    }
    #This dictionary stores how many coins are in each bag.
    coinWeight = {    '2' : 12,   '1' :  9.5,   '0.50' : 8,  '0.20' : 5,   '0.10' :  6.5,  '0.05' : 3.25,'0.02' : 7.12, '0.01' : 3.56, }
    #This dictionary stores how much the 1 of each coin weighs. The values are in grams.
    AddCoins = True     #This defines a variable for whether to add/remove coins.    
    differentWeight = idealWeight[denomination] - bagWeight
    #This calculation works out how the difference in weight between the 'ideal' bag weight and the actual bag weight.
    coinInBag = bagWeight/coinWeight[denomination]
    #This calculation works out how many coins are in each bag. It does this by, dividing the bag weight by how much each coin weighs.  
    coinChange = bagCoins[denomination] - coinInBag
    #Calculating the amount of coin difference in the bag

    if differentWeight < 0:
        AddCoins = False
        differentWeight = differentWeight  * -1
        coinChange = coinChange * -1

    if AddCoins == True:
        print('The bag is ',str(differentWeight), 'g less than it should be')
        print('Add ', int(coinChange), ' coin(s)')
        totalCoinsAdd = totalCoinsAdd + coinChange

    if AddCoins == False:
        print('The bag is ',str(differentWeight), 'g more than it should be')
        print('Remove ', int(coinChange), ' coin(s)')
        totalCoinsRemoved = totalCoinsRemoved + coinChange

again = 'yes'
while again != 'no':
    inputs()
    totalBagsChecked = totalBagsChecked + 1
    again = input('Would you like to weight another bag? ("no" to quit)')

print('Total coins added: ', int(totalCoinsAdd))
print('Total coins removed: ', int(totalCoinsRemoved))
print('Total bags checked:', int(totalBagsChecked))

Answer 1

多信息源

您有4个数据结构(1个list和3个字典)，它们的内容需要保持同步，因为列表中的值必须是字典的键，而列表中没有的字典中的键是没有意义的。

如果你只有一个真理的单一来源，事情可能会更清楚。例如，您可以有一个到idealWeight、bagCoins和coinWeight的单字典映射值(不管它的意思是什么)。Python通过元组或名称s提供了简单的实现方法。

FOr实例，您可以执行如下操作：

from collections import namedtuple
bagWeight = 0
totalCoinsAdd = 0
totalCoinsRemoved = 0
totalBagsChecked = 0

CoinInfo = namedtuple('CoinInfo', ['idealWeight', 'bagCoins', 'coinWeight'])

COINS = {
    '2':    CoinInfo(120,  10, 12),
    '1':    CoinInfo(190,  20,  9.5),
    '0.50': CoinInfo(160,  20,  8),
    '0.20': CoinInfo(250,  50,  5),
    '0.10': CoinInfo(325,  50,  6.5),
    '0.05': CoinInfo(325, 100,  3.25),
    '0.02': CoinInfo(356,  50,  7.12),
    '0.01': CoinInfo(356, 100,  3.36),
}

def inputs():    
    global bagWeight
    global totalCoinsAdd
    global totalCoinsRemoved 
    #The above grabs the global variables for use in the function    
    bagWeight = int(input("How much does the bag weigh? "))    
    denomination = ""
    while denomination not in COINS:
        denomination = input("What denomination is the money? £")
    coin = COINS[denomination]
    AddCoins = True     #This defines a variable for whether to add/remove coins.    
    differentWeight = coin.idealWeight - bagWeight
    #This calculation works out how the difference in weight between the 'ideal' bag weight and the actual bag weight.
    coinInBag = bagWeight/coin.coinWeight
    #This calculation works out how many coins are in each bag. It does this by, dividing the bag weight by how much each coin weighs.  
    coinChange = coin.bagCoins - coinInBag
    #Calculating the amount of coin difference in the bag

AddCoinss变量

注释This defines a variable for whether to add/remove coins.非常冗长，可以是一个简单的Add/remove coins。

顺便说一句，这里有一个叫做PEP 8的风格指南，它非常值得一读，如果你没有任何理由不去读它(遗留项目、公司代码风格等等)，它是值得一读的。除其他外，它还指出snake_case应该用于变量(而不是CamelCase)。

另外，我们以后检查它的方式可以改进，原因有两个：

• 当变量(或任何表达式)已知为布尔值时，最好编写if var (resp )。( if not var)而不是if var == True (resp.if var == False)。在现实生活中，你会说“如果下雨”，而不是“如果真的下雨”。
• 检查if AddCoins == True，然后在if AddCoins == False之后检查，而不更改AddCoins的值。这正是else关键字的作用所在。它使代码对读者来说更加清晰，因为乍一看，我们将只通过一个块。

到目前为止，我们已经：

add_coins = True  # Whether to add/remove coins.
if differentWeight < 0:
    add_coins = False
    differentWeight = differentWeight  * -1
    coinChange = coinChange * -1

if add_coins :
    print('The bag is ',str(differentWeight), 'g less than it should be')
    print('Add ', int(coinChange), ' coin(s)')
    totalCoinsAdd = totalCoinsAdd + coinChange
else:
    print('The bag is ',str(differentWeight), 'g more than it should be')
    print('Remove ', int(coinChange), ' coin(s)')
    totalCoinsRemoved = totalCoinsRemoved + coinChange

现在，这个变量一点也不有用，因为我们正在执行真正重要的测试(differentWeight < 0)，我们可以直接在这里处理不同的处理。

此外，在这里，变量名也可以改进，您可以使用var *= -1而不是var = var * -1。

代码看起来应该是：

if different_weight < 0:
    different_weight *= -1
    coinChange *= -1
    print('The bag is ',str(different_weight), 'g more than it should be')
    print('Remove ', int(coinChange), ' coin(s)')
    totalCoinsRemoved = totalCoinsRemoved + coinChange
else:
    print('The bag is ',str(different_weight), 'g less than it should be')
    print('Add ', int(coinChange), ' coin(s)')
    totalCoinsAdd = totalCoinsAdd + coinChange

正如马蒂亚斯·埃廷格的S评论所指出的，您最好完全去掉乘法，在打印时只考虑负值：

if different_weight < 0:
    print('The bag is ',str(-different_weight), 'g more than it should be')
    print('Remove ', int(-coinChange), ' coin(s)')
    totalCoinsRemoved = totalCoinsRemoved - coinChange
else:
    print('The bag is ',str(different_weight), 'g less than it should be')
    print('Add ', int(coinChange), ' coin(s)')
    totalCoinsAdd = totalCoinsAdd + coinChange

字符串格式

Python提供了不同的格式化字符串的方法，向print提供多个参数并不是最喜欢的方法。您可以在网上找到关于字符串格式设置的文档，但是可以找到pyformat.info提供了一个非常好的摘要。

使用此方法，您可以编写如下内容：

    if different_weight < 0:
        print('The bag is {}g more than it should be'.format(-different_weight))
        print('Remove {} coin(s)'.format(-coinChange))
        totalCoinsRemoved = totalCoinsRemoved - coinChange
    else:
        print('The bag is {}g less than it should be'.format(different_weight))
        print('Add {} coin(s)'.format(coinChange))
        totalCoinsAdd = totalCoinsAdd + coinChange

again = 'yes'
while again != 'no':
    inputs()
    totalBagsChecked = totalBagsChecked + 1
    again = input('Would you like to weight another bag? ("no" to quit)')

print('Total coins added: {}'.format(totalCoinsAdd))
print('Total coins removed: {}'.format(totalCoinsRemoved))
print('Total bags checked: {}'.format(totalBagsChecked))

全局变量

一般来说，使用全局变量是个坏主意，它往往表明代码的组织方式存在问题。

无论如何，bagWeight不需要是一个全局变量。

Answer 2

我想说的是，你应该把这些清单合并成一个。例如

coins = {'1p':[356,3.56,0.01]}

所有的硬币都可以这样做。最后的价值等于硬币的货币价值(以英镑为单位)。

这就是我的例子：

#A variable to count the number of bags processsed
count = 0
#The function to check the weights of the bags and display the number of coins needed to be added or removed
def check(bag_weight, coin_type, bag_weight1):
    #import the variable 'count' into the function
    global count
    #Add 1 to the number of bags counted
    count = count+1
    #Find the maximum number of coins allowed in the bag
    x = bag_weight1[coin_type]
    y = x[1]
    #Check if the bag exceeds the maximum weight allowed
    if bag_weight > y:
        #If it does take the maximum away from the actual weight and display how much too heavy the bag is
        print("you have",int(bag_weight - y), "too many coins")
    else:
        #Otherwise take the actual weight from the maximum weight and display number of coins needed to be added
        print("you need to add",int(y - bag_weight), "coins")





#Starting function to get all necassary information for calculation to begin
def main():
    #Forever iterate through this loop
    while True:
        #Display the number of bags already checked
        print("you have checked", count, "bags.")
        #Ask if the user wants to weigh a bag
        y = input('do you want to check a bag?(Y/N)')
        #If answer is yes continue, other wise jump to the 'else' statement
        if y.lower() == 'y':
            #Get user to input the weight of the bag
            weight = float(input('how heavy is the bag(grams)?'))
            #Dictionary of lists containing vital information about the different types of coin the format: weight of coin, maximum number of coins allowed in the bag
            coin_Weight = {'1p':[3.56, 100],'2p':[7.12, 50],'5p':[3.25,100],'10p':[6.5, 50],'20p':[5.0, 50],'50p':[8.00, 20],'£1':[9.50, 20],'£2':[12.00, 10]}
            #Input the type of coin in the bag
            coin_type = input('what type of coin is it?(1p, 2p, 5p, 10p, 20p, 50p, £1, £2)')
            #Get the corresponding list of information from the dictionary about the coin
            bag_weight1 = coin_Weight[coin_type]
            #Divide the actual weight of the bag by the weight of one coin to find the number of coins in each bag
            bag_weight = weight/bag_weight1[0]
            #Output the number of coins in the bag allong with the type of coin
            print('there are', int(bag_weight), coin_type, 'coins in the bag.')
            #Initiate further calculation by passing the following arguments into the function 'check'
            check(bag_weight, coin_type, coin_Weight)
        #If the user answered 'no' continue into this part of the loop
        else:
            #Print a message thanking the user for using the program
            print("Thank you for using this program.")
            #Break out of the loop
            break
#Call the function 'main' to begin the program
main()