On 2014-12-08 23:58, Ben Finney wrote:
memilanuk <memila...@gmail.com> writes:
What I'm having trouble finding a concrete answer to is the difference
between:
(Note that where you write “some_func” the syntax requires an
expression, not a function. I've changed your examples to be clear).
lambda: some_expr
This creates a new function which expects zero parameters. The function,
when called, will return the value of ‘some_expr’.
lambda x: some_expr
This creates a new function which expects one positional parameter named
‘x’. The function, when called, will return the value of ‘some_expr’.
lambda x=some_value: some_expr
This creates a new function which expects one parameter named ‘x’, which
parameter has a default value of ‘some_value’. The function, when
called, will return the value of ‘some_expr’.
This is useful when you want to 'capture' the current value of
'some_value' to be passed to some_expr; if you didn't, then some_expr
would be using the value of 'some_value' at the time it was called,
which might be different if some variable it used had been changed.
Any help would be greatly appreciated.
Hope that helps.
It's best to remember that ‘lambda’ is syntactic sugar for creating a
function; the things it creates are not special in any way, they are
normal functions, not “lambdas”.
What is different is that the function starts with no name bound to it,
and the syntax allows only a single expression as the body of the
function.
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