Python, Ruby, Perl: Loop Examples

Xah Lee, 2005-01-15, …, 2012-12-16

Python

This is a example of “for” loop.

# -*- coding: utf-8 -*-
# python

aa = range(1, 10) # creates a list, 1 to 9
for xx in aa:
    print xx                    # prints 1 to 9

Python also supports “break” and “continue” to exit the loop. “break” will exit the loop. “continue” will skip code and start the next iteration.

Here's a example of using “break”.

#-*- coding: utf-8 -*-
# python

for x in range(1, 10):          # 1 to 9
    print x
    if x == 4:
        break                   # prints 1 to 4

http://docs.python.org/reference/compound_stmts.html#for

#-*- coding: utf-8 -*-
# python

x = 1
while x <= 9:
    print x
    x += 1

http://docs.python.org/reference/compound_stmts.html#while

Ruby

#-*- coding: utf-8 -*-
# ruby

aa = 1..9                     # creates a array 1 to 9
for xx in aa do
  p xx
end                               # prints 1 to 9

Note: Ruby also supports loop controls {break, next}.

#-*- coding: utf-8 -*-
# ruby

for xx in 1..9 do
  p xx
  if xx == 4 then break end
end                             # prints 1 to 4

#-*- coding: utf-8 -*-
# ruby

x = 1;
while x <= 9 do
  p x
  x += 1
end

Perl

This is similar code in Perl.

#-*- coding: utf-8 -*-
# perl

@aa = (1..9); # creates a array 1 to 9
for $xx (@aa) {
  print $xx
}                               # ⇒ 123456789

Note: Perl also supports loop controls “next”, “last”, “goto” and few others.

#-*- coding: utf-8 -*-
# perl

for $xx (1..9) {
  print $xx;
  if ($xx == 4) {
    last;                       # break
  }
}                               # ⇒ 1234

#-*- coding: utf-8 -*-
# perl

$x = 1;
while ($x <= 9) {
  print $x, "\n";
  $x++;
}

• perldoc perlsyn
• perldoc -f next
• perldoc -f last
• perldoc -f goto