Kernel#p

p(object) -> object

Returns: Object · Updated March 13, 2026 · Kernel Methods

output debugging inspection printing

The p method outputs objects to STDOUT using their inspect method, making it ideal for debugging. Unlike puts which calls to_s, p shows the actual structure of objects.

Basic Usage

# Simple values
p "hello"    # => "hello"
p 42         # => 42
p [1, 2, 3]  # => [1, 2, 3]

# Returns the object
result = p [1, 2, 3]
# Prints: [1, 2, 3]
# Returns: [1, 2, 3]

p vs puts vs print

# puts calls to_s
puts "hello"   # hello (no quotes)
puts [1, 2]   # 1
              # 2

# p calls inspect  
p "hello"     # "hello" (with quotes)
p [1, 2]      # [1, 2]

# print is like puts but no newline
print "hi"   # hi (no newline)

Practical Examples

Debugging Arrays

data = [1, "hello", {key: "value"}]
p data
# Output: [1, "hello", {:key=>"value"}]
# (shows the actual structure)

Debugging Hashes

config = { debug: true, port: 8080 }
p config
# Output: {:debug=>true, :port=>8080}

Multiple Arguments

# p accepts multiple arguments
x = 10
p x, x*2, x*3
# Output:
# 10
# 20
# 30

In Methods

def process_data(input)
  p input  # Debug print
  # ... process
  p input  # Debug print after
end

With Objects

class User
  attr_accessor :name, :age
  
  def initialize(name, age)
    @name = name
    @age = age
  end
end

user = User.new("Alice", 30)
p user
# Output: #<User:0x00007f8a2c003a80 @name="Alice", @age=30>

Chaining

# p returns its argument, so it can be chained
result = p p [1, 2, 3]
# Prints:
# [1, 2, 3]
# [1, 2, 3]
# Returns: [1, 2, 3]

IRB/Console Debugging

# In IRB or Rails console
p variables
p params
p ENV["PATH"]

Use Cases

Debugging variable values
Inspecting complex data structures
Quick logging during development
Seeing exact object types