How to create functors?

Robert Dailey rcdailey at gmail.com
Tue Aug 18 22:42:59 CEST 2009


On Aug 18, 3:40 pm, Chris Rebert <c... at rebertia.com> wrote:
> On Tue, Aug 18, 2009 at 1:32 PM, Robert Dailey<rcdai... at gmail.com> wrote:
> > On Aug 18, 3:31 pm, Duncan Booth <duncan.bo... at invalid.invalid> wrote:
> >> Robert Dailey <rcdai... at gmail.com> wrote:
> >> > Hello,
>
> >> > I want to simply wrap a function up into an object so it can be called
> >> > with no parameters. The parameters that it would otherwise have taken
> >> > are already filled in. Like so:
>
> >> >       print1 = lambda: print( "Foobar" )
> >> >       print1()
>
> >> > However, the above code fails with:
>
> >> >   File "C:\IT\work\distro_test\distribute_radix.py", line 286
> >> >     print1 = lambda: print( "Foobar" )
> >> >                          ^
> >> > SyntaxError: invalid syntax
>
> >> > How can I get this working?
>
> >> def print1():
> >>     print "Foobar"
>
> >> It looks like in your version of Python "print" isn't a function. It always
> >> helps if you say the exact version you are using in your question as the
> >> exact answer you need may vary.
>
> > I'm using Python 2.6. And using the legacy syntax in the lambda does
> > not work either. I want to avoid using a def if possible. Thanks.
>
> chris at morpheus ~ $ python
> Python 2.6.2 (r262:71600, May 14 2009, 16:34:51)
> [GCC 4.0.1 (Apple Inc. build 5484)] on darwin
> Type "help", "copyright", "credits" or "license" for more information.>>> print1 = lambda: print( "Foobar" )
>
>   File "<stdin>", line 1
>     print1 = lambda: print( "Foobar" )
>                          ^
> SyntaxError: invalid syntax>>> from __future__ import print_function
> >>> print1 = lambda: print( "Foobar" )
> >>> print1()
>
> Foobar
>
> Cheers,
> Chris
> --http://blog.rebertia.com

I see what you're saying now. However, why am I able to use print as a
function in general-purpose code in my Python 2.6 script, like so:

def SomeFunction():
   print( "Hello World" )

But, I am not able to do this:

SomeFunction = lambda: print( "Hello World" )

??????

Doesn't make sense.



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