4. (12 points) Choose several different numbers from $1, 2, 3, 4, 5, 6, 7$ (the order of the selected numbers does not matter), such that the sum of the even numbers equals the sum of the odd numbers. The number of ways to select the numbers that meet the condition is $\qquad$.
4. (12 points) Choose several different numbers from $1, 2, 3, 4, 5, 6, 7$ (the order of the selected numbers does not matter), such that the sum of the even numbers equals the sum of the odd numbers. The number of ways to do this is $\qquad$.

【Solution】Solution: Among $1,2,3,4,5,6,7$, $1,3,5,7$ are odd numbers, and $2,4,6$ are even numbers;
$$
\begin{array}{l}
3+5=2+6 \\
1+7=2+6 \\
1+5=2+4 \\
1+3=4 \\
1+5=6 \\
3+7=4+6 \\
5+7=2+4+6
\end{array}
$$

There are 7 ways in total;
Answer: There are 7 ways that meet the conditions.
Therefore, the answer is: 7.