qquark

  irb(main):001:0> a = 1
  => 1
  irb(main):002:0> class Integer
  irb(main):003:1>   def hello
  irb(main):004:2>     puts "world"
  irb(main):005:2>   end
  irb(main):006:1> end
  => :hello
  irb(main):007:0> a.hello
  world
  => nil

  >>> x = 1
  >>> f"{x}"
  '1'

  >>> "{x}".format(x=x)
  '1'

  >>> "{}".format(x)
  '1'

  >>> exec("def f(" + ",".join("f" + str(x) for x in range(300)) + "): print(f299)")
  >>> f(*range(300))
  299
  >>> exec("f(" + ", ".join(str(i) for i in range(300)) + ")")
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
    File "<string>", line 1
  SyntaxError: more than 255 arguments

  >>> exec("f(" + ", ".join(str(i) for i in range(30)) + ")")
  Traceback (most recent call last):
    File "<stdin>", line 1, in <module>
    File "<string>", line 1, in <module>
  TypeError: f() takes exactly 300 arguments (30 given)