虽然python循环不能正常工作？

时间：2017-10-27 08:48:01

标签： python python-3.x while-loop

我正在通过使用python自动化无聊的东西来学习python，并且随着我在最初章节的进展，我决定尝试编写与作者目的不同的代码。在毒理学课上，老师说一种蜗牛每年死亡率高达12％。所以我决定制作一个代码来计算它。

我制作的代码是：

number= input('Number of individuals: ')  #tells the number of individuals in the beggining
count = 0 #tells the nuumber of generations
number=int(number)
percent=input('% of loss per generation ')  #% of individuals lost in each generation
percent=int(percent)

#while number > 1:
 #   number= number*(percent*0.01)
  #  number=round(number,-1)
   # count = count +1
    #print('generation ' + str(count) + ':' + str(number*0.1) + ' individuals')
    #if number == 1:
     #   print(' it took ' + str(count) + ' generations to end with the species')


while True:
    if number == 1:
        print(' it took ' + str(count) + ' generations to end with the species')
    if number >1:
        number= number*(percent*0.01)
        number=round(number,-1)
        count = count +1
        print('generation ' + str(count) + ':' + str(number*0.1) + ' individuals')
    if number == 0 :
        break

我试图制作的第一个代码是在评论中，我试图用另一种方法来尝试解决我的问题。

我的问题是： 我想输入个人数量和损失百分比。最后（因为个体不能与自己交配，这是1），我希望它告诉我结束这个物种所需的世代数。当程序循环比它假定的时间多一个时（和之前我使用round（）函数它甚至循环更多次）问题开始了，因为我不想要0值，并且当它达到1时我想要它告诉我用它结束了多少代。

我试图寻找答案，但因为我是初学者，我可能无法正确理解正确搜索的条款。 我看到它的方式，程序应该像我想的那样运行，但我想我错过了一些我没有得到的东西。

5 个答案:

答案 0 :(得分：0)

看看这个。

number = input('Number of individuals: ')  # tells the number of individuals in the beggining
count = 0  # tells the nuumber of generations
number = int(number)
percent = input('% of loss per generation ')  # % of individuals lost in each generation
percent = int(percent)

while number > 1:
    number = number * (1 - percent * 0.01)
    number = int(number)
    count = count + 1
    print('generation ' + str(count) + ':' + str(number) + ' individuals')
print(' it took ' + str(count) + ' generations to end with the species')

包括@Alans的建议。

永无止境的循环问题的发生是因为最终只有一小部分人死于“死亡”。在您的round(number, -1)四舍五入后，例如从5个人中死亡0.3人，所以4.7仍然存在，但是四舍五入使他们再次成为5人。 int(number)向下舍入。

答案 1 :(得分：0)

让我们在评论中讨论代码，因为它是一个更好的解决方案，只需要一些改进。您的代码中存在两个主要问题

1）为什么要打印number * 0.1而不是number？它显示1应该显示10，我相信这是误导你的主要问题。

print('generation ' + str(count) + ':' + str(number*0.1) + ' individuals')

2）以下两行必须不在循环中，因为实际上你可以传递1到und将永远不会看到结果消息。这些行必须放在循环之后：

if number == 1:
    print(' it took ' + str(count) + ' generations to end with the species')

这是我们的结果：

number= input('Number of individuals: ')  # tells the number of individuals in the beggining
count = 0 # tells the nuumber of generations
number=int(number)
percent=input('% of loss per generation ')  # % of individuals lost in each generation
percent=int(percent) * 0.01

while number > 1:
    number = number * percent
    number = round(number)
    count = count +1
    print('generation ' + str(count) + ':' + str(number) + ' individuals')

print(' it took ' + str(count) + ' generations to end with the species')

<强>更新

如果您不介意，可以应用一些次要代码样式改进代码：

更新＃2：

我只修复了循环，但正如@Alan在评论中指出的那样，你计算了错误。百分比应为1 - int(percent) * 0.01 

number = input('Number of individuals: ')  # tells the number of individuals in the beggining
number = int(number)
percent = input('% of loss per generation ')  # % of individuals lost in each generation
percent = 1 - int(percent) * 0.01

count = 0 # tells the nuumber of generations
while number >= 2:
    number = number * percent
    count += 1
    print('generation {}: {} individuals'.format(count, round(number)))    

print(' it took {} generations to end with the species.'.format(count))

尝试代码https://repl.it/NWi4/2

更新＃3：

我修改了代码块以改进舍入。它是round(number, -1)，导致了数十的四舍五入。

答案 2 :(得分：0)

首先，你以错误的方式计算了活蜗牛的数量，每个迭代蜗牛都应该有（100％ - 损失％）*蜗牛。 第二件事是条件和圆函数。您的代码很容易陷入损失不足以使前一个数字在舍入后降低的点，例如。 4 * 0.88 = 3.52，四舍五入后再次为4。因此，您可以根据问题的性质从舍入或使用楼层辞职。问题是我们如何治疗0.52的蜗牛？

对于12％的损失和100个人，花了37代才结束了没有四舍五入的物种，并且在使用地板时花了24代才结束物种。

以下代码应该有效。 

import numpy as np
while True:
        if number <= 1: # <= covers values below 1
            print(' it took ' + str(count) + ' generations to end with the species')
            break;
        if number > 1:
            number = number*(1-percent*0.01) # number left is 1 - minus loss percent
            # number = np.floor(number) # optional floor
            count = count + 1
            # print('generation ' + str(count) + ':' + str(number*0.1) + ' individuals')

答案 3 :(得分：0)

您的代码有两个问题：

  1. 错误的舍入 - 您正试图以负值（如-2）进行舍入。四舍五入时需要使用正数。
  2. 每次迭代减少数量

    3. number = number - number*percent*0.01

    只需在代码中更改以上两项内容即可。

    更改后的代码： 

    number= input('Number of individuals: ')  #tells the number of individuals in the beggining
count = 0 #tells the nuumber of generations
number=int(number)
percent=input('% of loss per generation ')  #% of individuals lost in each generation
percent=int(percent)

while True:
    if number <= 1:
        print(' it took ' + str(count) + ' generations to end with the species')
        break
    if number > 1:
        number = number - number*percent*0.01
        number = round(number,2)

        count = count +1
        print('generation ' + str(count) + ':' + str(number*0.1) + ' individuals')
        print "Number is ",number
    if number == 0 :
        break

    <强>输出： 

    Number of individuals: "10"
% of loss per generation "2"
generation 1:0.98 individuals
Number is  9.8
generation 2:0.96 individuals
Number is  9.6
generation 3:0.941 individuals
Number is  9.41
generation 4:0.922 individuals
Number is  9.22
generation 5:0.904 individuals
Number is  9.04
generation 6:0.886 individuals
Number is  8.86
generation 7:0.868 individuals
Number is  8.68
generation 8:0.851 individuals
Number is  8.51
generation 9:0.834 individuals
Number is  8.34
generation 10:0.817 individuals
Number is  8.17
generation 11:0.801 individuals
Number is  8.01
generation 12:0.785 individuals
Number is  7.85
generation 13:0.769 individuals
Number is  7.69
generation 14:0.754 individuals
Number is  7.54
generation 15:0.739 individuals
Number is  7.39
generation 16:0.724 individuals
Number is  7.24
generation 17:0.71 individuals
Number is  7.1
generation 18:0.696 individuals
Number is  6.96
generation 19:0.682 individuals
Number is  6.82
generation 20:0.668 individuals
Number is  6.68
generation 21:0.655 individuals
Number is  6.55
generation 22:0.642 individuals
Number is  6.42
generation 23:0.629 individuals
Number is  6.29
generation 24:0.616 individuals
Number is  6.16
generation 25:0.604 individuals
Number is  6.04
generation 26:0.592 individuals
Number is  5.92
generation 27:0.58 individuals
Number is  5.8
generation 28:0.568 individuals
Number is  5.68
generation 29:0.557 individuals
Number is  5.57
generation 30:0.546 individuals
Number is  5.46
generation 31:0.535 individuals
Number is  5.35
generation 32:0.524 individuals
Number is  5.24
generation 33:0.514 individuals
Number is  5.14
generation 34:0.504 individuals
Number is  5.04
generation 35:0.494 individuals
Number is  4.94
generation 36:0.484 individuals
Number is  4.84
generation 37:0.474 individuals
Number is  4.74
generation 38:0.465 individuals
Number is  4.65
generation 39:0.456 individuals
Number is  4.56
generation 40:0.447 individuals
Number is  4.47
generation 41:0.438 individuals
Number is  4.38
generation 42:0.429 individuals
Number is  4.29
generation 43:0.42 individuals
Number is  4.2
generation 44:0.412 individuals
Number is  4.12
generation 45:0.404 individuals
Number is  4.04
generation 46:0.396 individuals
Number is  3.96
generation 47:0.388 individuals
Number is  3.88
generation 48:0.38 individuals
Number is  3.8
generation 49:0.372 individuals
Number is  3.72
generation 50:0.365 individuals
Number is  3.65
generation 51:0.358 individuals
Number is  3.58
generation 52:0.351 individuals
Number is  3.51
generation 53:0.344 individuals
Number is  3.44
generation 54:0.337 individuals
Number is  3.37
generation 55:0.33 individuals
Number is  3.3
generation 56:0.323 individuals
Number is  3.23
generation 57:0.317 individuals
Number is  3.17
generation 58:0.311 individuals
Number is  3.11
generation 59:0.305 individuals
Number is  3.05
generation 60:0.299 individuals
Number is  2.99
generation 61:0.293 individuals
Number is  2.93
generation 62:0.287 individuals
Number is  2.87
generation 63:0.281 individuals
Number is  2.81
generation 64:0.275 individuals
Number is  2.75
generation 65:0.269 individuals
Number is  2.69
generation 66:0.264 individuals
Number is  2.64
generation 67:0.259 individuals
Number is  2.59
generation 68:0.254 individuals
Number is  2.54
generation 69:0.249 individuals
Number is  2.49
generation 70:0.244 individuals
Number is  2.44
generation 71:0.239 individuals
Number is  2.39
generation 72:0.234 individuals
Number is  2.34
generation 73:0.229 individuals
Number is  2.29
generation 74:0.224 individuals
Number is  2.24
generation 75:0.22 individuals
Number is  2.2
generation 76:0.216 individuals
Number is  2.16
generation 77:0.212 individuals
Number is  2.12
generation 78:0.208 individuals
Number is  2.08
generation 79:0.204 individuals
Number is  2.04
generation 80:0.2 individuals
Number is  2.0
generation 81:0.196 individuals
Number is  1.96
generation 82:0.192 individuals
Number is  1.92
generation 83:0.188 individuals
Number is  1.88
generation 84:0.184 individuals
Number is  1.84
generation 85:0.18 individuals
Number is  1.8
generation 86:0.176 individuals
Number is  1.76
generation 87:0.172 individuals
Number is  1.72
generation 88:0.169 individuals
Number is  1.69
generation 89:0.166 individuals
Number is  1.66
generation 90:0.163 individuals
Number is  1.63
generation 91:0.16 individuals
Number is  1.6
generation 92:0.157 individuals
Number is  1.57
generation 93:0.154 individuals
Number is  1.54
generation 94:0.151 individuals
Number is  1.51
generation 95:0.148 individuals
Number is  1.48
generation 96:0.145 individuals
Number is  1.45
generation 97:0.142 individuals
Number is  1.42
generation 98:0.139 individuals
Number is  1.39
generation 99:0.136 individuals
Number is  1.36
generation 100:0.133 individuals
Number is  1.33
generation 101:0.13 individuals
Number is  1.3
generation 102:0.127 individuals
Number is  1.27
generation 103:0.124 individuals
Number is  1.24
generation 104:0.122 individuals
Number is  1.22
generation 105:0.12 individuals
Number is  1.2
generation 106:0.118 individuals
Number is  1.18
generation 107:0.116 individuals
Number is  1.16
generation 108:0.114 individuals
Number is  1.14
generation 109:0.112 individuals
Number is  1.12
generation 110:0.11 individuals
Number is  1.1
generation 111:0.108 individuals
Number is  1.08
generation 112:0.106 individuals
Number is  1.06
generation 113:0.104 individuals
Number is  1.04
generation 114:0.102 individuals
Number is  1.02
generation 115:0.1 individuals
Number is  1.0
 it took 115 generations to end with the species

答案 4 :(得分：0)

根据Iosif Serafeimidis的回答，这将继续减少人口，直到减少量小于1。正如其他人所说，答案实际上取决于你想要表达的内容。请注意，round（number）将舍入到最接近的整数，而不是int（number），它会舍入到下一个最小的整数。这是修改后的版本：

number = input('Number of individuals: ')  # tells the number of individuals in the beginning
count = 0  # tells the nuumber of generations
number = int(number)
percent = input('% of loss per generation ')  # % of individuals lost in each generation
percent = int(percent)

while number > 1:
    reduction = number * (percent * 0.01)
    if reduction < 1:
        print('No further reductions possible')
        break
    number = round(number - reduction)
    count = count + 1
    print('generation ' + str(count) + ':' + str(number) + ' individuals')

print(' after ' + str(count) + ' generations, there were ' + str(number) + ' individuals')
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