Hi @Rockkley.

Lambdas are anonymous callable objects. If you want call it later, you must use a variable, no other choice to do that. And here (in codewars) if there no name, unit test cannot check the solution.

For your information, in python, a def (and so, a fonction) defined like that create a variable:

def foobar(): pass

The variable created is foobar, the proof, you can do that:

def foobar(): pass
foobar = 1234

It's the aim of the mechanism under the concept of decorators.

If you prefer i can use these solutions instead of lambda, the solution will be acepted:

# Common accepted solution
def check(s, e): return e in s

# Another solution
def singleton(c): return c()
@singleton
class check:
  def __call__(self, s, e):
    return e in s

I know that lambda is anonymous function, and there's no need to create variable for lambda, but here we need to meet the interface requirements. Requirement here is that check is callable.

In real world I would not create function for this one liner, that's why I'm showing solution with lambda.

variable "check" holds the function. and ambda describes the oneliner function.

mult = lambda a,b:a*b

is the same as

def mult(a,b):
return a*b

What do you mean? Do you know how lambdas work? Do you know you can copy the code and make trials on your own to understand how it works? On your own computer, or just here, by clicking on Forkjust below any solution.

Why creating a variable for lambda?

You need more corner-case tests here

This comment got deleted.

I'm not happy with this kata. Using builtin function is not cheating when in description is no information about not using this.
Also this "anti-cheat" was not giving me option to name my variable max :/

Hi, message ValueError: sample larger than population simply says that population (from what we want build sample) is smaller than number of elements we want to select.
In this case it suggests that [x for x in c.dict.keys() if not str(x).startswith('__')] is less than 1. And that means that you miss something in class created with your solution.

Hi, after attempts I have this error. Should it be visible or I just made something wrong?

Traceback (most recent call last):
File "main.py", line 60, in
rand = sample([x for x in c.dict.keys() if not str(x).startswith('__')], 1)[0]
File "/usr/local/lib/python2.7/random.py", line 325, in sample
raise ValueError("sample larger than population")
ValueError: sample larger than population