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{ 2008 06 21 }

Why I hate python

I recently wrote a small internal program in python to automate our client’s builds: run everything overnight, collect the output, and generate some rudimentary web pages It wound up being 250 loc for the program, split into about three files; and 500 loc for the tests. I spent about 2-5 days on it, part time. Just enough to give me a feel for what the language is like.

And I don’t like the language. I know that python is supposed to be the cool language, and perl is ugly line noise. And ruby? I don’t know what people have against ruby. But python is so sexy they even use it to teach the Intro to Computer Science course at Harvey Mudd now.

I hate the way formatting structures control flow. I hate that even in XEmacs in python-mode, I was fighting with it to get the right indentation (which means the right semantics). I hate that I can’t define an empty class or method. Several times I started to write a test, realized I wanted to run something first, and left it stubbed out as


  def testHTMLLine:

Well, you can’t do that. You need to do:


  def testHTMLLine:
      pass

At that point I’ll bring my own curly braces.

I hate that it’s dynamic, but not dynamic enough. I had a set of tests, collected into about five test cases. One set of tests was slow (10 seconds) because it actually tested connecting to the CVS server, checking out a project, building it, etc. The rest of the tests finished in under a second. I wanted to define a test suite that contained all the fast tests only, so I could shorten my test-code-test cycles.

Simple and evil solution: enumerate the test cases that are fast. Evil because I have to remember to update the list if I add a new fast test case. So create a suite at module level like this:


fastTests = ["test.TestParseOutputLog", "test.TestDirClass", "test.TestSystem" ]
fastSuite = unittest.TestLoader().loadTestsFromNames( fastTests )

Clever and dynamic solution: enumerate all the tests but remove the slow ones.

# NOTE: not actually python, this DOESN'T WORK
fastTests = __thismodule__.Classes.remove( "SlowTest" )
fastSuite = unittest.TestLoader().loadTestsFromNames( fastTests )

I couldn’t figure out how to easily enumerate all the classes in the module I was in. While loading the module, some of the things which get set up eventually (the module object, for example) are not yet available to me. Look, I know it’s possible because the unittest.main() routine knows how to enumerate all the classes which are descended from unittest.TestCase. But it’s not trivial to do. In ruby you could do something like

fastTests = []
ObjectSpace.each_object( Class ) { |x| fastTests << x.to_s if x =~ /^Test/ }
fastTests.delete("TestSlow")

where you could filter on name (starts with Test) and file (if necessary), and then remove the slow one. This isn’t about dynamic vs. static languages, it’s about user experience. In C you know you can’t do reflection, and when a unit test framework like cxxtest depends on perl or Python being installed, that’s fine. But because it’s possible in Python — but obscure and ill-documented — it becomes an annoyance.

The documentation is horrible. Over the last ten years my first recourse when looking for API documentation has been my friend Google. The Python documentation, even though it’s all free and available online, seems to be deliberately poorly organized and indexed. What I was hoping for was a quick cheat sheet on how to do a common thing (string interpolation). What I found was proposals to change or extend Python in varying mutually incompatible ways, in order to make it easier to do string interpolation. And this experience was repeated over and over as I dug through the language, library, and ancillary documentation looking for the Python way to do the things I needed.

Finally, Python doesn’t live up to its hype. How can it support functional programming when expression if (as opposed to statement if) was only added as a language feature in version 2.5? Even C has it!

Perhaps I have this all wrong, and Python is the best language EVAH. In the spirit of Strong Opinions, Weakly Held I welcome corrections and arguments in the comments.

Posted by Sam_old on Saturday, June 21, 2008, at 1:06 pm. Filed under Languages. Tagged . Follow any responses to this post with its comments RSS feed. You can post a comment or trackback from your blog.