[Tutor] lambda: print('x') raises SyntaxError?

[wcyee]

Ahh. It seems so obvious now. :)

Thanks, Wesley & Kent!


On 7/5/07, wesley chun <wescpy at gmail.com> wrote:
>
> On 7/5/07, Kent Johnson <kent37 at tds.net> wrote:
> > wc yeee wrote:
> > > Hi. Is there a reason the code below raises a syntax error? It's
> > > probably something silly on my part, but I can't figure it out:
> > >
> > >
> > >  >>> b = lambda: print('bar')
> > >   File "<stdin>", line 1
> > >     b = lambda: print('bar')
> > >                              ^
> > > SyntaxError: invalid syntax
> >
> > The body of a lambda has to be an expression, not a statement. print is
> > a statement.
> > >
> >
> > > This works fine too:
> > >
> > >  >>> import sys
> > >  >>> a = lambda: sys.stdout.write('foo\n')
> > >  >>> a()
> > > foo
> >
> > Right, that is an expression and it is the workaround for your original
> > problem.
>
>
> one thing to keep in mind when thinking, "is this an expression or a
> statement?" is that the former will always evaluate to some sort of
> Python object (numerical calculation, function return value [your case
> above], some string you've built, etc.) whereas the latter will not
> have any kind of intrisic value (print, while, if, class, def... none
> of these have a "value").
>
> on a partially-related note, print will be changing to a function in
> the next generation of Python... see PEP 3105:
>
> http://www.python.org/dev/peps/pep-3105/
>
> for a list of some of the other changes coming down the line:
> http://www.python.org/dev/peps/pep-3100/
>
> cheers,
> -- wesley
> - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
> "Core Python Programming", Prentice Hall, (c)2007,2001
>     http://corepython.com
>
> wesley.j.chun :: wescpy-at-gmail.com
> python training and technical consulting
> cyberweb.consulting : silicon valley, ca
> http://cyberwebconsulting.com
>
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