What does this mean: key=lambda x: x[1] ?

Question

I see it used in sorting, but what do the individual components of this line of code actually mean?

key=lambda x: x[1]

What\'s lambda

Answer 1

lambda effectively creates an inline function. For example, you can rewrite this example:

max(gs_clf.grid_scores_, key=lambda x: x[1])

Using a named function:

def element_1(x):
    return x[1]

max(gs_clf.grid_scores_, key=element_1)

In this case, max() will return the element in that array whose second element (x[1]) is larger than all of the other elements' second elements. Another way of phrasing it is as the function call implies: return the max element, using x[1] as the key.