Ruby equivalent for Python's "try"?

Question

I'm trying to convert some Python code into Ruby. Is there an equivalent in Ruby to the try statement in Python?

Look up Ruby `rescue` (and `raise`) – lurker Sep 09 '13 at 19:21 — lurker, Sep 09 '13 at 19:21

Óscar López · Accepted Answer · 2022-08-31T08:23:30.917

134

Use this as an example:

begin  # "try" block
    puts 'I am before the raise.'  
    raise 'An error has occurred.' # optionally: `raise Exception, "message"`
    puts 'I am after the raise.'   # won't be executed
rescue # optionally: `rescue StandardError => ex`
    puts 'I am rescued.'
ensure # will always get executed
    puts 'Always gets executed.'
end

The equivalent code in Python would be:

try:     # try block
    print('I am before the raise.')
    raise Exception('An error has occurred.') # throw an exception
    print('I am after the raise.')            # won't be executed
except:  # optionally: `except Exception as ex:`
    print('I am rescued.')
finally: # will always get executed
    print('Always gets executed.')

edited Aug 31 '22 at 08:23

answered Sep 09 '13 at 19:22

Óscar López

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There's also the quirky `else` clause that gets executed only if no exceptions have been triggered. – tadman Sep 09 '13 at 19:32
this is most easieast answer and understandable, thanks thanks – Jenuel Ganawed Mar 23 '20 at 02:33
1

one of the best answers on SO from both a form and content perspective; much thanks – d8aninja Dec 01 '20 at 13:17
1

It's better to rescue `StandardError` instead of `Exception` (as in the comment in the Ruby example): https://stackoverflow.com/q/10048173/12484 – Jon Schneider Aug 30 '22 at 22:02

score 13 · Answer 2 · answered Sep 09 '13 at 19:21

13

 begin
     some_code
 rescue
      handle_error  
 ensure 
     this_code_is_always_executed
 end

Details: http://crodrigues.com/try-catch-finally-equivalent-in-ruby/

answered Sep 09 '13 at 19:21

zengr

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Great link! It's really helpful. – thatonegirlo Sep 09 '13 at 19:29

score 3 · Answer 3 · answered Apr 01 '19 at 20:29

If you want to catch a particular type of exception, use:

begin
    # Code
rescue ErrorClass
    # Handle Error
ensure
    # Optional block for code that is always executed
end

This approach is preferable to a bare "rescue" block as "rescue" with no arguments will catch a StandardError or any child class thereof, including NameError and TypeError.

Here is an example:

begin
    raise "Error"
rescue RuntimeError
    puts "Runtime error encountered and rescued."
end

Ruby equivalent for Python's "try"?

3 Answers3