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Tuesday, 27 November 2007

Two years of Python

As last Wednesday was the second anniversary of me joining Google, I thought it an opportune time to reflect on how I've found learning Python.

It's no big secret that Google is a Python shop. I'd been meaning to learn it a for a while prior to joining Google, but never found enough reason to other than because it seemed to be the cool new language. If I had a task that required me to write a script, I could do it in Perl in 30 minutes, or spend a day trying to wrap my head around how to do it Python.

I think I'd known and been writing Perl in some form or other for about 9 years. I've hardly written any in the last two, which is a bit sad. I even bought Perl Best Practices shortly after moving over here, and haven't gotten around to reading it. The only Perl I write these days is for personal tasks to try and stop myself from going totally rusty.

Anyway, I thought I'd write down some of my observations of Python, from a "veteran" Perl programmer's perspective. Not that I consider myself to be a shit-hot Perl coder by any stretch of the imagination...

No punctuation

I really like the lack of punctuation. It makes the code look a lot cleaner. I go back to Perl and my eyes bleed after trying to dereference a reference to a scalar, or something like that. It's just ugly in Perl.

No curly braces/indentation for blocks

The indentation thing isn't so bad. If you're using vi, you really need something along the lines of

set shiftwidth=2
set smarttab
set autoindent
set expandtab

in your ~/.vimrc

What I do miss is being able to bounce on the % key to find the beginning and ending of a block. I've heard rumours of a way to configure vi to do something similar for Python code, but I haven't gotten around to finding out. There seems to a general opinion that if you're writing a block that is so big you can't find the beginning and end of it, you're probably doing something wrong.

String concatenation

It's always struck me as bizarre how the most obvious way to concatenate a string in Python is also one of the least efficient. In fact, there's whole studies been done into different methods of string concatenation and their efficiencies.

Prototyping is easy

Now I may just be ignorant of some Perl shell here, but the number of times I've written a quick Perl script in /tmp to do some proof-of-concept thing is immeasurable. The fact that you can just fire up a Python interpreter and try something quick and dirty to see if it's syntactically sane, or does what you expect is fantastic time saver. ipython makes it an even more pleasant an experience.


I was initially a bit disappointed that there wasn't something like CPAN for Python modules. In practice, using Debian, I haven't found this to be that big a problem though.

List joining is wacky

I still find it weird that you don't join a list by a method of the list, you do it by a method of the string you want to use to join the list together with, that is, I think it should be mylist.join(" ") when it's really " ".join(mylist). That's just always struck me as unintuitive.

urllib2 doesn't hold a candle to libwww-perl

I think even last time I checked with Python 2.5, it's impossible to make a HEAD request. The mind boggles.

No setuid support

I can't complain too much, I think I heard somewhere it's going away in Perl as well, but it was certainly very convenient to be able to write setuid Perl scripts. I miss that convenience in Python. Not that one has to write setuid scripts all that often.

Regular expression handling is painful

It's about on a par with Java. You just can't beat Perl's =~ operator.

"There's more than one way to do it" versus only one way to do it

Perl's always had the adage of there being more than one way to do things. I think that has been its downfall in terms of readability. Heck, I've written some monstrosities that I've looked back on in a month's time and wondered what on earth I was thinking at the time. I think it's far easier to write readable Python than it is to write readable Perl.

I think that's about everything. I never did any real object-oriented programming in Perl, and so I tend to take a procedural approach to things in Python as well. I haven't written any massive bodies of code in Python (although I did help maintain one for about 18 months).

I like Python. It's become my first choice for writing random scripts now. Now I look at Ruby like I used to look at Python when I knew Perl quite well. Ruby has some nice things (like Perlish regular expression handling), but it brings back all that punctuation noise again. I'm not in a huge rush to learn it, even though there's a lot of hype around Ruby on Rails. I think I'd rather investigate Django or Pylons

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