How To Let People Know You're A Bad Python Programmer

Re:How To Let People Know You're A Bad Python Programmer by blasdel on Friday August 28, 2009 @03:16PM (#792056)

Of course functions are first-class, and the lambda statement does return anonymous functions. Functions in Python are just objects that have a __call__ method, and methods are just functions partially-applied to the object they are bound on -- LOVELY METACIRCULARITY

What aren't first class are statements and suites (indented blocks of expressions) -- they're part of the syntax and thus can't be constructed or referred to. Particularly nasty is the way non-value-returning statements can't be used in expressions passed to other statements.

Your example is perfect -- in Python < 3, print is a statement and not a built-in function!

  # this is invalid syntax:
  name_printer = lambda x: lambda: print x
  
  # with print as a function it works:
  from __future__ import print_function
  name_printer = lambda x: lambda: print(x)

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Re:How To Let People Know You're A Bad Python Programmer by erlanger on Friday August 28, 2009 @03:32PM (#792090)

Nice explanation. Note that I did wrap my print arg in parens, however. When I heard they were changing it to a function in 3 I made this a habit.

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Re:How To Let People Know You're A Bad Python Programmer by blasdel on Friday August 28, 2009 @04:04PM (#792171)

Using parens that way with the print statement is a bad idea. You aren't using it like a function -- the parens are parsed as an expression.

                 statement   function
  print(1)       1           1
  print(1,2)     (1, 2)      1 2
  print(1,2), 3  (1, 2) 3    SyntaxError

Just use the old syntax, and let 2to3 take care of you when the time comes.

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Re:How To Let People Know You're A Bad Python Programmer by erlanger on Friday August 28, 2009 @06:09PM (#792387)

I don't think I've ever used print that way. If I need to print more than one thing, it's clearer to use regular string formatting. Thanks for clarifying that though, interesting.

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