crazy lambdas

Steven D. Majewski sdm7g at virginia.edu
Wed Feb 14 04:32:13 CET 2001


On Wed, 14 Feb 2001, Dan Parisien wrote:

> I want to do this
> 
> e.callbacks.append(lambda d=dict, p=person: del d[p])
> 
> # .... later
> 
> e.trigger() #deletes
> ---
> those who use lambdas alot will notice my mistake. I, however, do not know 
> what I am doing wrong. I think it has something to do with the fact 'del 
> d[p]' doesn't have a value...

No -- the problem is that 'lambda' expressions take an expression
and 'del' is a statement in the python grammar. 

You'll get the same error if you try: 'lambda x: import sys' --
The problem is 'del' , not 'd[p]' . 

> Is it possible to do what I want (make a custom one-time-use function that 
> is called much later and deletes a key from a dictionary)?


I think the more pythonic way to do this would be to subclass
UserDict and make a method that deletes the keys. 


---|  Steven D. Majewski   (804-982-0831)  <sdm7g at Virginia.EDU>  |---
---|  Department of Molecular Physiology and Biological Physics  |---
---|  University of Virginia             Health Sciences Center  |---
---|  P.O. Box 10011            Charlottesville, VA  22906-0011  |---
		"All operating systems want to be unix, 
		 All programming languages want to be lisp." 





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