solution

test.py

class Solution:
    def addOperators(self, num, target):
        length = len(num)
        
        ret = []
        
        def rdfs(curr_index, curr_calculate, curr_expr):
            if curr_index >= length:
                if curr_calculate == target:
                    ret.append(curr_expr)
            else:
                for i in range(curr_index+1, len(num)+1):
                    if num[curr_index: i] == '00': break
                    n = int(num[curr_index: i])
                    
                    print (f'curr_index: {curr_index}, curr_calculate: {curr_calculate}, curr_expr: {curr_expr}, n: {n}')
                    
            
                    if n == 0:
                        rdfs(curr_index+i+1, eval(curr_expr+'0'), curr_expr+'0')

                    rdfs(i, curr_calculate + n, '{}+{}'.format(curr_expr, n))
                    rdfs(i, curr_calculate - n, '{}-{}'.format(curr_expr, n))
                    rdfs(i, eval('{}*{}'.format(curr_expr, n)), '{}*{}'.format(curr_expr, n))
        
        rdfs(1, int(num[0]), str(num[0]))
        return ret