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> first-class. I'm not sure I follow. This looks first-class to me. def name_printer(name): def printer(): print(name) return printer

> first-class. I'm not sure I follow. This looks first-class to me. def name_printer(name): def printer(): print(name) return printer erlanger_printer = name_printer('erlanger') Python doesn't support creating anonymous functions, but functions are first-class. Sorry if you already knew this; it seems like you know Python pretty well so I'm sure you do.

blasdel 17y ago
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)
- erlanger 17y ago
  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.
  - blasdel 17y ago
    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.
    - erlanger 17y ago
      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.

blasdel 17y ago

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)

erlanger 17y ago
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.
- blasdel 17y ago
  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.
  - erlanger 17y ago
    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.