Reduce() function

The function reduce (func, seq) continually applies the function func() to the sequence seq. It returns a single value.

If seq= [ s1, s2, s3, ... , sn ], calling reduce(func,seq) works like this:

• At first the first two elements of seq will be applied to func, i.e. func(s1,s2). The list on which reduce() works looks now like this: [func(s1, s2), s3, ... ,sn]
• In the next step func will be applied on the previous result and the third element of the list, i.e. func(func(s1, s2),s3). The list looks like this now: [func(func(s1, s2),s3), ... ,sn]
• Continue like this until just one element is left and return this element as the result of reduce()

We illustrate this process in the following example:

reduce(lambda x,y: x+y, [47,11,42,13])

The following diagram shows the intermediate steps of the calculation: