Ruby equivalent of Python's "dir"?

In Python we can "dir" a module, like this:

>>> import re
>>> dir(re)

And it lists all functions in the module. Is there a similar way to do this in Ruby?

As far as I know not exactly but you get somewhere with

object.methods.sort

I like to have this in my .irbrc:

class Object
  def local_methods
    (methods - Object.instance_methods).sort
  end
end

So when I'm in irb:

>> Time.now.local_methods 
=> ["+", "-", "<", "<=", "<=>", ">", ">=", "_dump", "asctime", "between?", "ctime", "day", "dst?", "getgm", "getlocal", "getutc", "gmt?", "gmt_offset", "gmtime", "gmtoff", "hour", "isdst", "localtime", "mday", "min", "mon", "month", "sec", "strftime", "succ", "to_f", "to_i", "tv_sec", "tv_usec", "usec", "utc", "utc?", "utc_offset", "wday", "yday", "year", "zone"]

Or even cuter - with grep:

>> Time.now.local_methods.grep /str/
=> ["strftime"]

Tip for "searching" for a method in irb:

"something".methods.select {|item| item =~ /query/ }

Tip for trying out methods on a value for comparison:

value = "something"
[:upcase, :downcase, :capitalize].collect {|method| [method, value.send(method)] }

Also, note that you won't get all the same information as Python's dir with object.methods. You have to use a combination of object.methods and class.constants, also class.singleton_methods to get the class methods.

You can send the methods method to a value. It will list all the methods the value responds to.

>> "a string".methods
=> [:unicode_normalize, :unicode_normalize!, :ascii_only?, :to_r, :encode, ... ]

There are other methods like this, such as instance_methods which you can read about in the docs: e.g https://ruby-doc.org/core-2.7.3/Module.html#instance_methods-method

I'd go for something like this:

y String.methods.sort

Which will give you a yaml representation of the sorted array of methods. Note that this can be used to list the methods of both classes and objects.

Maybe not answering the original question (depends on the use case), but for those who are looking for this to be used in the irb only, you can use "double-TAB" for autocompletion. Which, effectively, can also list (almost all) the methods available for a given object.

Put the following line into your ~/.irbrc file:

require 'irb/completion'

Now, (re)start the irb, start typing a method and hit TAB twice - irb autocompletes the input!

I actually learned it here: http://drnicwilliams.com/2006/10/12/my-irbrc-for-consoleirb/

Not really. Like the others said, you can get part of what you want by listing class instance methods (e.g. String.instance_methods) but that doesn't help you if a file you open reopens a class (unless you check before and after).

If you don't need programmatic access to the list of methods, consider checking out the documentation for a class, module or method using the ri command line tool.

I would have made this a comment to jonelf's answer, but apparently I don't have enough rep.

some_object.methods.sort - Object.new.methods

This isn't exactly what you were asking as others have said, but it gives you the info you are after.

If I stricly read your question, I must answer it that way: a file as specified by require in Ruby is just a container and does not have necessarely have any relation with a class. The content can be:

• a class
• a module
• plain code

or any combination of the above, several times. So you can not directly ask for all methods in a given file.

If you meant to list all methods of a given module or class, then the other answers are what you seek (mainly using the #methods method on a module name or class).