Set Matrix Zeroes

def solve(matrix):
    m = len(matrix[0])
    n = len(matrix)
    flag_row,flag_column = False ,False
#flag marking
    for i in range(n):
        if matrix[i][0]==0:
            flag_column = True
            break
            
    for j in range(m):
        if matrix[0][j]==0:
            flag_row = True
            break
            
#mark zero on edges    
    for i in range(1,n):
        for j in range(m):
            if matrix[i][j]==0:
                matrix[0][j]=0
                matrix[i][0]=0
                
#painting zero marked row and columns                
    for i in range(1,n):
        if matrix[i][0]==0:
            for a in range(1,m):
                matrix[i][a]=0
                
    for j in range(m):
        if matrix[0][j]==0:
            for a in range(1,n):
                matrix[a][j]=0

#painting first raw and column if flag is on
    if flag_column==True:
        for i in range(n):
            matrix[i][0]=0
            
    if flag_row==True:
        for j in range(m):
            matrix[0][j]=0
    return matrix