require 'open3'
 
command = 'python /tmp/foo.py'
 
Open3.popen3(command) { |stdin, stdout, stderr| p stdout.read }   # 1.
 
p `#{command}`  # 2.
p %x{#{command}}  # 3.
system(command)  # 4.
 
# 5.
IO.popen(command, 'r+') do |io|   
        p io.read
end