Ruby equivalent to Python's help()?

Question

When working in interactive Python, I tend to rely on the built-in help() function to tell me what something expects and/or returns, and print out any documentation that might help me. Is there a Ruby equivalent to this function?

I'm looking for something I could use in irb. For example, in interactive Python I could type:

>>> help(1)

which would then print

Help on int object:

class int(object)  |  int(x[, base])
-> integer  |    |  

Convert a string or number to an integer, if possible. A ...

Answer 1

It's now late 2014 and here's the two ways to get the Python help() *similarity, as long as you have the Ruby Docs installed:

1. From inside irb, You can call the help method with a string describing what you're looking for.

   Example 1: help 'Array' for the Array class
   Example 2: help 'Array#each' for the Array class each method.

2. From the command line, outside of irb, you can use the ri program:

   Example 1: ri 'Array' for the Array class
   Example 2: ri 'Array#each' for the Array class each method.

* Not quite as good as Python's, but still better than nothing

Answer 2

It's definitely a poor cousin to iPython's help, and one of the main features I miss after moving to Ruby, but you can also use ri from within irb. I'd recommend the wirble gem as an easy way to set this up.

Answer 3

Try using ri from the command line.

It takes a class name, method, or module as an argument, and gives you appropriate documentation. Many popular gems come with this form of documentation, as well, so it should typically work even beyond the scope of core Ruby modules.