Pry is the enhancement of Ruby REPL irb, equivalent of Python's IPython.

Install, start and show help

Check and install:

gem search pry
gem info -b pry  # search Both local and remote, by default only local
gem install pry pry-doc pry-byebug pry-theme awesome_print coderay

Note: gem install pry-full failed with dependency error.

Start Pry inside irb and show help:

> require 'pry'
> binding.pry
> help

Frequently Used Commands

hist       # show command history
.pwd       # run shell command with `.` prefix
cd myobj1  # go into an object
whereami   # print the context where the debugger is stopped
ls         # list methods of `myobj`
method1    # equals to `myobj1.method1`
cd ..      # go out of myobj1
reset      # clear pry environment

Toggle shell-mode with shell-mode.

Show doc: ? method-name or show-doc ..., ri ....

Show source codes of a method: $ method-name or show-source ....

Run shell command with . prefix.

Define new command or aliases

The following command add some aliases and a new command into Pry session:

cat << EOF >> ~/.pryrc
Pry.editor = 'nvim'
Pry.config.commands.alias_command "w", "whereami"
Pry.config.commands.alias_command "n", "next"
Pry.config.commands.alias_command "c", "continue"
Pry.config.commands.alias_command "b", "break"
Pry.config.commands.alias_command "s", "step"
Pry.config.commands.alias_command "bt", "backtrace"
Pry.config.commands.command "l", "Load a Ruby file into current session" do |filename|
  Pry.toplevel_binding.eval File.read("#{filename}.rb")
end
EOF

Debug

Debug a ruby script by adding a binding.pry at the debugging point, like set_trace() for IPython.

To debug a script, run ruby myscript.rb in shell, or load 'myscript.rb' in pry REPL. It will be stopped at the line binding.pry. Then you can use next, continue, etc to debug the script. Using help in pry REPL to list available commands. All aliases defined in ~/.pryrc are listed in section "Aliases". All debugging commands are listed in section "Byebug". See pry-byebug for details.

A minimum demo script:

require 'pry'

binding.pry

class Number < Struct.new(:value)
  def to_s
    value.to_s
  end
end

n = Number.new(53)
puts(n.to_s)

Run pry-theme list in pry REPL to show all themes.

Ref:

Better pry for Ruby REPL

Notes

To open tab completion and auto indention in irb, add the following lines into ~/.irbrc:

require 'irb/completion'

IRB.conf[:AUTO_INDENT] = true

Or using Bond, gem install bond and add the following into ~/.irbrc:

require 'bond'
Bond.start