A common task that is very useful when dealing with lists or other sequences of data is to apply the same operation to each element of the list and then collect the result. For example, a list update may be done in the following way from the Python IDLE:
>>>items = [1,2,3,4,5,6,7,8,9,10] >>>updated_items =  >>>for x in items: >>> updated_items.append(x*2) >>> updated_items >>> [2, 4, 6, 8, 10, 12, 14, 16, 18, 20]
This is a common operation. However, Python has a built-in feature that does most of the work.
The Python function
map(aFunction, aSequence) applies a passed-in function to each item in an iterable object and returns a list containing all the function call results. Now, the same example would be:
>>>items = [1,2,3,4,5,6,7,8,9,10] >>>def multiplyFor2(x):return x*2 >>>print(list(map(multiplyFor2,items))) >>>[2, 4, 6, 8, 10, 12, 14, 16, 18, 20]