2, reduce () function
reduce () function is also built-in python a higher-order function. reduce function received parameters () and map () is similar to a function f, a list, but the behavior and map () different, reduce () function f must receive the incoming two parameters, reduce () for each of the list repeatedly calling the function f elements, and returns the final result value.
For example, a write function, receiving x, y, returns the x, y and hair:
def f(x,y)
return x+y
When calling reduce (f, [2,6,9]), reduce the function is calculated as follows:
First calculate the first two elements: f (2,6), the result is 4;
The results of the three elements and then calculates: f (4,9), the result is 13;
When the above calculation is actually summing all elements of the list. Although the python built-sum function sum (), however, the use of reduce () is also very simple summation
reduce () may also receive a third optional parameter, calculated as the initial value. If the initial value is 100. Calculated:
reduce(f,[2,6,9],100)
Results becomes 113, as the first round of calculation:
And calculating the initial value of the first element: f (100,1), the result is 101.
python built-sum function sun (), but no sum function, please use reduce () to Quadrature:
Input: [2,4,5,7,12]
Output: Results 2 * 4 * 7 * 12
reduce () function f receiving two arguments, and returns a result, in order to continue the next round of calculation
as follows:
