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Code Challenge 14 - Write DRY Code With Decorators - Review

Posted by PyBites on Sat 15 April 2017 in Challenges • 2 min read

It's end of the week again so we review the code challenge of this week: Write DRY Code With Decorators. It's never late to join, just fork us and start coding.

Our solution and learning

Getting our hands on decorators we enriched our Python toolkit! This one was also a lot of fun. See our solution here. We did a simple timeit one and a more complex mute_exception one. For the latter we needed this week's article: How to Write a Decorator with an Optional Argument?.

Some other things we learned:

  • Know the stdlib. Part of what makes these decorators useful is knowing about time, random, the @wraps decorator, partial, the awesome logging module, etc.

  • As we sensed using optional arguments made the mute_exception more versatile. You can run it in various ways:

    @mute_exception                                    # works: no args provided = takes defaults (no reraise, returns None)
    @mute_exception(reraise=True)                      # works: raises the ZeroDivisionError = crash
    @mute_exception(reraise=False, default_return=0)   # works: does not reraise ZeroDivisionError and returns 0 in that case
  • We used f-strings! We are on Python 3.6 now so we just could no longer resist the temptation :)

  • Our Flake 8 Check Vim shortcut pays off: the code is more readable.

  • Keep reading other blogs and books. We based these decorators on How to Create an Exception Logging Decorator and the almighty Python Cookbook, Third edition.

Output 2 stacked decorators

When you run our solution it will print (fake) timings and mute/log the ZeroDivisionError exception:

$ python

div of args: (1, 4) took 0.755037784576416
div 1/4 = 0.25

div of args: (2, 5) took 0.763498067855835
div 2/5 = 0.4

div of args: (3, 0) took 0.09057903289794922
div 3/0 = 0

The program did not crash by the divide by 0, logging the exception:

$ tail decorators.log
00:58:36 root         DEBUG    div called for args (1, 4)
00:58:36 root         DEBUG    div called for args (2, 5)
00:58:37 root         DEBUG    div called for args (3, 0)
00:58:37 root         ERROR    div raised exception ZeroDivisionError for args: (3, 0)


But there is more ... we got a nice PR with two other cool decorators:

  • boxit - a decorator to draw a box around text
  • hashit - a decorator to securely hash passwords (using passlib)

Next Up

As you might have noticed (here and here) we are learning Flask so we thought it would be a great topic for our next challenge coming Monday. Stay tuned ...

We hope you are enjoying these challenges, learning along the way. Let us know if you have any issue and/or contact us if you want to submit a cool challenge. See you next week ...

See an error in this post? Please submit a pull request on Github.