exec语句用来执行储存在字符串或者文件中的python语句
示例for i in range(m_no):
expr1 = '''self.m_{} = agent_machine.machine(env, {}, print = 0)'''.format(i,i) # create machines
exec(expr1)

exec语句用来执行储存在字符串或者文件中的python语句
示例for i in range(m_no):
expr1 = '''self.m_{} = agent_machine.machine(env, {}, print = 0)'''.format(i,i) # create machines
exec(expr1)