result of a function is difference with result of map-CodePudding

##Why the results of these two ways are different?##

my_list = [a, b, c]
def printable(x):return x*3
printable(my_list)

with this

list(map(printable,my_list)

CodePudding user response：

When the * operator is used on a list, the result is just that list repeated n times. For example, [1, 2, 3] * 3 would yield [1, 2, 3, 1, 2, 3, 1, 2, 3].

However if you want to multiply each element of the list by a number n, you'd use the second method. The map() function returns a map object(which is an iterator) of the results after applying the given function to each item of a given iterable (list, tuple etc.)

That is why you are getting different results.

CodePudding user response：

Checking the Python docs for map, we can see that it takes map(function, iterable) in which it applies the function to every item in iterable.

In this particular case, it seems like you only want to provide one argument, which just happens to be an iterable itself. So we can wrap your argument with a list as such to get the desired result:

>> list(map(printable,[my_list]))[0]
>> ['a', 'b', 'c', 'a', 'b', 'c', 'a', 'b', 'c']

>> my_list = ['a', 'b', 'c']
>> def printable(x):return x*3
>> printable(my_list)
>> ['a', 'b', 'c', 'a', 'b', 'c', 'a', 'b', 'c']