When to use puts, print, and p in Ruby

September 05, 2023

Usually, programming languages have methods for printing out variables. Ruby is not an exception. We will explore the 3 popular methods for printing variables in the Ruby Programming language.

The print method

The way print(var) works is basically converting its value to a string by calling the to_s method on the object(everything is an object in Ruby) before printing the value and returning nil to its caller.

num = 123
print(num) # -> 123 => nil

The print method can be easily used for concatenating strings

num = 123
name = "Aleem"

print "The name of the boy is "
print name
print ", and his tag ID is: "
print num
print "."

# outputs everything on a single line
# -> The name of the boy is Aleem, and his tag ID is: 123

Having print as the last operation in a method should be avoided if returning nil is not the desired value

def check_print 
    print "This should print without a new line"
end

val = check_point 
# -> This should print withouit a new line
# Now p val would return nil

The puts method

puts method is not so different from the print method except for two scenarios:

• puts adds a new line character at the end of the printed value

print "hello World"
# -> Hello World
# -> nil
puts "Hello world"
# -> Hello world
# ->
# -> nil

• puts prints each element in an array on a new line

arr = [1,2,3,4,5,6]
    
print arr
# -> [1,2,3,4,5,6]
# -> nil
puts arr
# -> 1
# -> 2
# -> 3
# -> 4
# -> 5
# -> 6
# -> nil

The p method

This method can be seen as a debugging tool. It prints more than just the value of a variable, it can print the memory, the object it belongs to. A good name befitting the p method is the variable inspection method.

p STDERR
# -> <IO:<STDERR>>

puts STDERR
# -> <IO:0x000000013f888e58>

Notice that above we have printed the value of STDERR to the console. using the p method, the module that the constant belongs as well as its name is returned, while puts only returns the module and memory address of the STDERR constant.

Shalom 🙇