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Comment by nivertech | Hacker News Reader

One thing I dislike in Python's syntax is ":" at the end of some composite statements, i.e. "if X:" or "else:". "else" is reserved word, why do I need to append ":"?

Also how to do one-liners? ;)

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Just like semantic indentation, ":" is ABC's heritage. It was discovered that newbie programmers comprehend block operations better when they end with ":".

http://python-history.blogspot.com/2009/02/early-language-de...

back in time, there was several schools for language syntax design for composite statements:

1. "Open" statements (Pascal):

  IF x 
    THEN s1
    ELSE s2;

  IF x 
    THEN
      BEGIN
        s1;
        s2
      END
    ELSE
      BEGIN
        s3;
        s4
      END

  WHILE c DO s;

  WHILE c DO
  BEGIN
     s1;
     s2
  END

The problem with this design was need to use blocks (BEGIN ... END) and complex rules in case of nesting.

2. "Closed" statements (Algol 68)

  IF x 
    THEN 
       s1;
       s2
    ELSE 
       s3;
       s4
  FI // END IF

  WHILE c DO
     s1;
     s2
  OD // END WHILE

You can see new kind of parenthesis IF-FI, DO-OD, etc.

I more like "closed" syntax. But C syntax with it's brackets blocks "{...}" instead of "BEGIN...END" made this less an issue.

You can have a one-line "if" statement [1]:

  if a == 42: print "Yes" ; do_stuff()

It's true that you cannot have a "else" statement on the same line, however.

But in some cases, you could use a conditional expression instead [2]:

  x = f() if a == 42 else g()

[1] http://docs.python.org/reference/compound_stmts.html

[2] http://docs.python.org/reference/expressions.html#conditiona...

in this case plain old C syntax is much more readable:

x = (a==42) ? f() : g();

In this case I think the PEP8 spacing guidelines are counterproductive:

    f() if a==42 else g()

looks much more readable to me than

    f() if a == 42 else g()

I think that it's much more readable due to familiarity more than anything else. The C syntax for the ternary operator was the one thing that it took me the longest time to get used to when learning to program. I usually just ignored it because it was too hard to remember what it did. That said, I can easily read it now, but I still feel that the Python syntax is more understandable.

Which is more readable:

  > condition ? value1 : value2

  > value1 if condition else value2

Maybe the latter is just more readable to me because I'm used to reading Perl all day long that looks like:

  > die unless condition;
  > return true if condition;
  > return false
  >     if condition1 && condition2 && condition3;

That said, I'm also used to reading:

  > return condition1   ? value1
  >        : condition2 ? value2
  >        : condition3 ? value3
  >                     : value4;

and I still find the Python ternary operator more readable:

  > return value1 if condition1 else
  >        value2 if condition2 else
  >        value3 if condition3 else
  >        value4

Personally, I still have to think about what the ternary operator means every time I see it. It's just so nonobvious.

You can also write it this way, which is more similar to C:

  x = (a==42) and f() or g()

I think the FAQ answers this question nicely: http://docs.python.org/faq/design.html#why-are-colons-requir...

As a non expert developer, I hate to see one-liners (using lambda expressions) when I am inspecting open source code.

So I would prefer they were not possible :)

While one-liners are almost always bad, the lack of non-crippled anonymous functions is the one thing that really bothers me about Python. They don't /have/ to be on one line; see Ruby's each blocks, for instance.

Every once in a while this will be brought up and debated to death...

See my last attempt in Feb 2009: http://mail.python.org/pipermail/python-ideas/2009-February/...

If you like Python but not the ":", check out the Cobra language: http://cobra-language.com/samples/WordCount/. FWIW I do like the ":", reminds me of a TODO list; in fact my plain text notes tend to look like Python ;)

You can do one liners with lambda functions in Python. e.g:

lambda x: x*2

http://diveintopython.org/power_of_introspection/lambda_func...

The colon is there to make it easier on editors that want to do auto-indentation. Their logic can simply be that if the previous line ends with a colon, then add a new indentation level.

Now we supposed to help editors? ;) I thought it should be otherwise... editors supposed to be helping programmers.

Programmers can learn syntax. Regular humans can't. Both Python and Ruby failed to provide a simple way of building internal DSLs. In Python humans need to be specific about indentation and ":" and in Ruby they need to remember all these stupid sigils.

lambda functions are pretty neat for one-liners.

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