If you need to assign the
lambda to a name, use a
defs are just syntactic sugar for an assignment, so the result is the same, and they are a lot more flexible and readable.
lambdas can be used for use once, throw away functions which won't have a name.
However, this use case is very rare. You rarely need to pass around unnamed function objects.
filter() need function objects, but list comprehensions and generator expressions are generally more readable than those functions and can cover all use cases, without the need of lambdas.
For the cases you really need a small function object, you should use the
operator module functions, like
operator.add instead of
lambda x, y: x + y
If you still need some
lambda not covered, you might consider writing a
def, just to be more readable. If the function is more complex than the ones at
operator module, a
def is probably better.
So, real world good
lambda use cases are very rare.