practice at war的用法和样例：
- The two sisters are constantly at war with each other.
- The country has been at war with its neighbour for two years.
- Those two countries have been at war for a long time.
- He kept himself in practice at golfing.
- The coach let us out from practice at 3 o'clock.
- The state of being at war or being engaged in a warlike conflict.