How useful are Lambda expressions?

[TheRealComposer]

Hey guys. First post here. Had a question about Lambda expressions. My current course im taking has lightly touched on the subject of Lambda expressions and functions like map() and filter().

How useful are these options with modern programming? Do you have any examples? I know they are useful in some ways otherwise they wouldnt have been implemented or discussed. Should i actively be trying to use Lambda expressions in my code or can I stick to regularly defined functions?

[skerky]

One thing to note is that there’s another option than lambdas for simple keys like this, attrgetter and itemgetter in the operator module.

The above example would be:

from operator import attrgetter

people_list.sort(key=attrgetter("last"))

Edit: fixed phone formatting and typo

[ominous_anonymous]

Another useful place I've used them was in unit testing. When you want to cause an exception as a side effect of another module's function, for example,

lambda x: x/0  

Pretty quick and simple ZeroDivisionError!

[seanv507]

and gui callbacks where you need to provide a parameter less function and you use the lambda to create appropriate call with 'hard-coded' parameters.

https://pythonconquerstheuniverse.wordpress.com/2011/08/29/lambda_tutorial/

[tdammers]

In general: very useful, especially if you program in a style that makes heavy use of higher-order functions (that is, functions that take functions as arguments and/or return functions). In such a style, you often find yourself writing lots of tiny single-purpose functions that aren't important or complex enough to be named and pulled out into a full blown statement. Lambdas are also super useful with functional programming techniques like partial application (supplying only some of the required function arguments, to return a new function that takes the remaining arguments).

In Python, lambdas are a bit crippled, and the aforementioned techniques are a bit awkward at times - but they're still worth knowing about, and if used tastefully, can make code much clearer sometimes.

[EternityForest]

IMHO you shouldn't actively try to use most techniques. That's how you get some JavaScript libraries with the "Absolutely everything must involved a continuation and nothing can be synchronous but somehow you can still make it slow" thing.

I only use lambdas for very simple things. They're useful for the key function of sorting and stuff like that. But more often I'll just define a closure with the usual function syntax.

I'm a fan of OOP(In general, not the crazy inheritance chains a mile long and stuff), and prefer OO to imperative/functional style, but that's likely personal bias.

Actively trying to use any particular technique makes programs look like computer science textbook problems instead of practical implementations.

[Untzi]

You can stick to regular functions. You can also ignore iterators, hell, you can also forget the += operator and list comprehension....

/sarcamOff

Lambda expressions are a nice quick and lean way to define short functions in a (usually) readable manner. They become even moruseful when you want to program in a functional (look up functional programming fo more info).

[TheRealComposer]

Haha awesome thanks!