2 ms·
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,
by 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 agoNice 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 agoUsing 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 agoI 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.