Showing posts with label python. Show all posts
Showing posts with label python. Show all posts

Thursday, January 16, 2014

Python code indentation nightmare

After numerous hesitations, overcoming my intuitive distaste of Python as programming language, I finally decided to learn it. This is not just for getting familiar with the core coolness of Python and getting myself into Python mainstream, but more for not finding myself becoming a Java-mastodon (a-la COBOL-mastodon or FORTRAN-mastodon) in the next 10 years. So, I created a little project, and started to push lines of code into it.

My first experience with Python has not changed anything about my bad attitude towards Python syntax:
  • Code structures simply don't look fine without opening and closing curly braces, everything looks like a big unstructured mess.
  • Doc-strings written as a comment in the body(!), where I can write any crap I want simply don't feel like an API documentation to a class/method/function.
  • """, which can be used either as a multi-line comment separator or ... as a multi-line string separator when assigned to a variable. Isn't it weird? One of my university professors used to say: "If you wan't to confuse a man, either call two different things with the same name, or call two equal things with different names", and I totally agree with him.
  • Two forms: "import thing" and "from thing import another_thing". Why do I need both of them? Why can't I just use: "import thing.another_thing" or "import thing [another_thing]" like in Perl?
  • Indentation...

Indentation worth another post. I've spent about an hour trying to understand why Unit test, which I added to a forked project's test suite doesn't run:

class TestSchemes(TestCase):
    ...
    def test_find(self):
        work = Scheme.find('wlan0', 'work')
        assert work.options['wpa-ssid'] == 'workwifi'

 # Added my test:
 def test_mytest(self):
  work = Scheme.find('wlan0', 'work')
  work.delete()
  work = Scheme.find('wlan0', 'work')
  assert work == None

Trying to run - my test doesn't run, and there's no single error. I thought, may be test methods are registered somewhere (unlikely, but who knows..), but this wasn't the case. Maybe test_mytest is some registered name in Python? Tried another method names, but with no luck. Finally, I tried one more thing: copied and pasted one of the existing method's declarations using Vim's 'yy' and 'p' shortcuts, then renamed the pasted method name, and voila! That worked! Hm... What's the difference between:

    def test_mytest(self):
        work = Scheme.find('wlan0', 'work')
        work.delete()
        work = Scheme.find('wlan0', 'work')
        assert work == None

and:

 def test_mytest(self):
  work = Scheme.find('wlan0', 'work')
  work.delete()
  work = Scheme.find('wlan0', 'work')
  assert work == None

Right.. this is white-space against tab. I always indent my code using tabs, so the method I added was also indented using tabs. As it turns out, the original code was indented using spaces, so the new method simply wasn't recognized until I replaced all tabs with spaces. This is really really weird situation, when indentation characters have an effect on execution flow. Don't you agree?

To complete, I'd like to write a couple of warm words about Python. There are plenty of frameworks and libraries written in Python. GitHub is teeming with lots and lots of interesting and fun projects, from which you can learn. If you want to build a fast prototype, it's awesome. Not as awesome as Java + Maven, but still :-) I'm mastodon...

May the source be with you.