CODEWITHSUNDEEP
pythonrubyloops
CuriOne
CuriOne

Reputation: 103

How does Ruby's for loop work, (compared to Python)?

I am currently jumping onto the Ruby train and I have some basic Python knowledge, which I hoped would help me, however I am not clear as to how Ruby's 'for' loops work and my feeling is that they work differently when compared to Python.

An example could be the following python code:

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)

Which produces the following (I put random numbers in):

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

What would a Ruby equivalent of the for loop here be?

I tried to do it like so:

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}"

This however, produces the following error:

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

Any help is much appreciated.

Upvotes: 0

Views: 378

Answers (2)

Ryan Rebo
Ryan Rebo

Reputation: 1318

Using 'for' in Ruby is typically written using 'each', this is the more idiomatic way. If you care to read more about 'for vs each' you can right here.

A one-line liner (eliminating the 'do' that opens your block) could be:

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

Upvotes: 0

bjhaid
bjhaid

Reputation: 9762

change:

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

to:

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

if you insist on using the for loop then:

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

The for loop in ruby is a wrapper around each so the object you intend to iterate on must respond to each, noy in this case is a string an not an Enumerable object

Upvotes: 2

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