Question

我目前正在跳上Ruby列车，我有一些基本的Python知识，我希望能帮助我，但是我不清楚Ruby的'for'循环是如何工作的，我的感觉是它们在比较时的工作方式不同到Python。

一个例子可能是以下python代码：

print('Interest Calculator: ')
sumnum = eval(input('Enter your initial sum: '))
initnum = sumnum
rate = eval(input('Enter your interest rate: '))
noy = eval(input('Enter the number of years to calculate      your interest for: '))
for i in range(noy):
    sumnum = initnum * (1 + rate)

print('The value of your initial investment of £%s' %initnum, 'over the course of', noy, 'years is £%s' %sumnum)

产生以下内容（我随机输入数字）：

Interest Calculator: 
Enter your initial sum: 250
Enter your interest rate: 3
Enter the number of years to calculate your interest for: 7
The value of your initial investment of £250 over the course of 7 years is £1000

这里的for循环的Ruby等价物是什么？

我试着这样做：

puts 'Interest Calculator: '
puts 'Enter your initial sum: '
sumnum = gets
initsum = sumnum
puts 'Enter your interest rate: '
rate = gets
puts 'Enter number of years for your interest: '
noy = gets
for i in noy do
 sumnum = initsum * (1 + rate)
end

puts "The value of your investment of £#{initsum} over the course of #{noy} years is £#{sumnum}"

然而，这会产生以下错误：

Interest Calculator:
Enter your initial sum: 
250
Enter your interest rate: 
3
Enter number of years for your interest: 
7
~/RubymineProjects/ExploreRuby/InterestRate.rb:9:in `<top   (required)>': undefined method `each' for "7\n":String  (NoMethodError)
from -e:1:in `load'
from -e:1:in `<main>'

Process finished with exit code 1

非常感谢任何帮助。

Answer 1

变化：

for i in noy do
 sumnum = initsum * (1 + rate)
end

为：

noy.to_i.times do
 sumnum = initsum.to_i * (1 + rate)
end

如果你坚持使用for循环，那么：

for i in (1..noy.to_i) do
  sumnum = initsum.to_i * (1 + rate)
end

ruby中的for循环是each的包装器，因此您要迭代的对象必须响应each，noy在这种情况下是一个字符串不是Enumerable对象

Answer 2

在Ruby中使用'for'通常使用'each'编写，这是更惯用的方式。如果您想了解更多关于'for vs each'的信息，可以right here。

单线衬垫（消除打开挡块的'do'）可能是：

noy.to_i.times { sumnum = initsum.to_i * (1 + rate) }
end

Ruby的for循环是如何工作的（与Python相比）？

2 个答案: