Forbid map/filter with lambda

Rule request

Thesis

Forbid using lambda inside of map and filter.

# bad
map(lambda x: x*2, lst)
# good
(x*2 for x in lst)

# bad
filter(lambda x: x%2, lst)
# good
(x for x in lst if x%2)

# using functions instead of lambdas is ok
map(str, lst)
str(str.islower, lst)

Reasoning

Generator expressions are good, easier to read, faster, and even shorter.

[Jrryy]

I don’t say that lambda is good, use it everywhere. I say, that sometimes they are more suitable than generators or functions.

I totally agree with this statement. There are cases in which using lambdas makes your code cleaner, more readable, and even faster. There are also cases in which using them transforms you code into a mess of complicated functional nonsense. Finding a balance between lambdas, generators, and functions, is a must to write good code, but simply forbidding their usage will not necessarily improve someone’s code.

In my humble opinion, the usage of lambdas depends on the context and complexity of the code and thus forbidding it might be too strict for a big amount of developers.

[sobolevn]

@AlwxSin consider using real monads instead! (just joking 🙂 )