字典中的稀疏矩阵

Question

I just started to learn to program in Python and I am trying to construct a sparse matrix using Scipy package. I found that there are different types of sparse matrices, but all of them require to store using three vectors like row, col, data; or if you want to each new entry separately, like S(i,j) = s_ij you need to initiate the matrix with a given size.
My question is if there is a way to store the matrix entrywise without needing the initial size, like a dictionary.

Answer 1

You can use usual dictionary with tuples of two integers as indices. For example:

matrix = {}
matrix[5, 7] = 1
matrix[3, 8] = 5

Answer 2

No. Any matrix in Scipy, sparse or not, must be instantiated with a size.

Answer 3

dic={}
a,b=int(input("Enter the order:")),int(input())
for i in range(a):
    for j in range(b):
        c=int(input())
        if c!=0:
            dic[(i,j)]=c
if len(dic)<=(a+b)/2:
    print("sparse metrix")
else:
    print("non sparse metrix")

for i in range(a):
    for j in range(b):
        print(dic.get((i,j),0),end=" ")
    print()