An example introduction to Yang Hui's triangle method in Python

Program output needs to achieve the following effects:

[1]
[1,1]
[1,2,1]
[1,3,3,1]

......

Method: iteration, generator

def triangles()
    L = [1]
    while True:
        yiled L
        L =[1] + [L[i] + L[I+1] for i in range(len(L)-1)] + [1]
n = 0
for t in triangles():
    print(t)
    n += 1
    if n == 10:
        break

Implementation logic:

1. Since yield is the generator interrupt output, the first output is [1]

2. Continue the loop after yield under while. At this time, the list length is 1, substitute it len(L) in L, the result is [L[i]+L[i+1] for i in range(1-1)], which is a null value, so the output of yield L is [1,1]

3. At this time, the value of len(L) is 2, and substitution results in [L[i]+L[i+1] for i in range(2-1)] as [L[i]+L[ i+1] for i in range(1)], i can take the value 0, and after substitution, it is [L[0]+L[1]], and the values ​​of L[0] and L[1] are both 1 (It can be seen from the above results), so the output result is [1,2,1]

4. From the third article, it can be seen that the value of len(L) is 3 at this time, and substitution gives [L[i]+ L[i+1] for i in range(2)], the value of i is 0 and 1, and there are two values ​​output through the loop, both are 3, respectively represented by [L[0]+L[1]],[ L[1]+L[2]]

The above is the detailed content of An example introduction to Yang Hui's triangle method in Python. For more information, please follow other related articles on the PHP Chinese website!