E731 do not assign a lambda expression, use a def

Question

I get this pep8 warning whenever I use lambda expressions. Are lambda expressions not recommended? If not why?

Answer 1

Lattyware is absolutely right: Basically PEP-8 wants you to avoid things like

f = lambda x: 2 * x

and instead use

def f(x):
    return 2 * x

However, as addressed in a recent bugreport (Aug 2014), statements such as the following are now compliant:

a.f = lambda x: 2 * x
a["f"] = lambda x: 2 * x

Since my PEP-8 checker doesn't implement this correctly yet, I turned off E731 for the time being.