Dealing with Tuples in Erlang

Say in Python we have a function defined like this:

def foo(**kwargs):

    pass

In languages like Python, we can pass keyword arguments to a function like:

foo(a = 1, b = 2, c = 3, d = 1)

In Erlang the function may look like this:

foo(Args) -> ok.

A call to foo in Erlang would look like:

foo([{a, 1}, {b, 2}, {c, 3}, {d, 1}]).

In Python we could check if 'a' was passed in as a keyword argument with:

return 'a' in kwargs

Whereas in Erlang we need to do:

lists:keyfind('a', 1, Args)

Note that we are looking at the 1st element in our tuple (hence the 1 in the second argument and not a zero).

keyfind returns false if the key was not found, otherwise it returns the tuple

In Python, to find all keys with the value 1 we do:

[k for k, v in kwargs.items() if v == 1]

In Erlang we do:

lists:filter(fun({Key, Value}) -> Value == 1 end, Args).

and just in case you thought that

lists:keyfind(1, 2, Args).

would find all tuples with the second element equal to 1, it only returns the first tuple that it finds.