SyntaxError: Missing parentheses in call to ‘print‘. Did you mean print(e)?

在学习古月老师ROS第四课，启动机器人的键盘控制launch文件时报了这个error，下面是报错的内容：

process[mbot_teleop-1]: started with pid [4942]File "/home/zxf/catkin_ws/src/mbot_teleop/scripts/mbot_teleop.py", line 78print msg^
SyntaxError: Missing parentheses in call to 'print'. Did you mean print(msg)?
[mbot_teleop-1] process has died [pid 4942, exit code 1, cmd /home/zxf/catkin_ws/src/mbot_teleop/scripts/mbot_teleop.py __name:=mbot_teleop __log:=/home/zxf/.ros/log/4e9341ca-0155-11ec-8ec5-cf95496c0738/mbot_teleop-1.log].
log file: /home/zxf/.ros/log/4e9341ca-0155-11ec-8ec5-cf95496c0738/mbot_teleop-1*.log

网上搜索了一圈发现是因为python2.x的版本与python3.x版本不兼容的问题。报错的原因就出在print输出语法上，一个简单的例子hello ROS

python2.x
print "hello ROS"
输出：hello ROS
print 'hello ROS'
输出：hello ROS
print ('hello ROS')
输出：hello ROS
print ("hello ROS")
输出：hello ROS

上面四种方法在python2.x中都可以适用，但在python3.x中却不一定

python3.x
print("hello ROS")
输出：hello ROS
print(hello ROS)
输出：hello ROS

我用的是ubuntu20.04，所以是python3的版本，与古月老师用的不一样所以需要修改~/catkin_ws/src/mbot_teleop/scripts/mbot_teleop.py文件

#!/usr/bin/env python
# -*- coding: utf-8 -*-import rospy
from geometry_msgs.msg import Twist
import sys, select, termios, ttymsg = """
Control mbot!
---------------------------
Moving around:u    i    oj    k    lm    ,    .q/z : increase/decrease max speeds by 10%
w/x : increase/decrease only linear speed by 10%
e/c : increase/decrease only angular speed by 10%
space key, k : force stop
anything else : stop smoothlyCTRL-C to quit
"""moveBindings = {'i':(1,0),'o':(1,-1),'j':(0,1),'l':(0,-1),'u':(1,1),',':(-1,0),'.':(-1,1),'m':(-1,-1),}speedBindings={'q':(1.1,1.1),'z':(.9,.9),'w':(1.1,1),'x':(.9,1),'e':(1,1.1),'c':(1,.9),}def getKey():tty.setraw(sys.stdin.fileno())rlist, _, _ = select.select([sys.stdin], [], [], 0.1)if rlist:key = sys.stdin.read(1)else:key = ''termios.tcsetattr(sys.stdin, termios.TCSADRAIN, settings)return keyspeed = .2
turn = 1def vels(speed,turn):return "currently:\tspeed %s\tturn %s " % (speed,turn)if __name__=="__main__":settings = termios.tcgetattr(sys.stdin)rospy.init_node('mbot_teleop')pub = rospy.Publisher('/cmd_vel', Twist, queue_size=5)x = 0th = 0status = 0count = 0acc = 0.1target_speed = 0target_turn = 0control_speed = 0control_turn = 0try:print(msg)print(vels(speed,turn))while(1):key = getKey()# 运动控制方向键（1：正方向，-1负方向）if key in moveBindings.keys():x = moveBindings[key][0]th = moveBindings[key][1]count = 0# 速度修改键elif key in speedBindings.keys():speed = speed * speedBindings[key][0]  # 线速度增加0.1倍turn = turn * speedBindings[key][1]    # 角速度增加0.1倍count = 0print(vels(speed,turn))if (status == 14):print(msg)status = (status + 1) % 15# 停止键elif key == ' ' or key == 'k' :x = 0th = 0control_speed = 0control_turn = 0else:count = count + 1if count > 4:x = 0th = 0if (key == '\x03'):break# 目标速度=速度值*方向值target_speed = speed * xtarget_turn = turn * th# 速度限位，防止速度增减过快if target_speed > control_speed:control_speed = min( target_speed, control_speed + 0.02 )elif target_speed < control_speed:control_speed = max( target_speed, control_speed - 0.02 )else:control_speed = target_speedif target_turn > control_turn:control_turn = min( target_turn, control_turn + 0.1 )elif target_turn < control_turn:control_turn = max( target_turn, control_turn - 0.1 )else:control_turn = target_turn# 创建并发布twist消息twist = Twist()twist.linear.x = control_speed; twist.linear.y = 0; twist.linear.z = 0twist.angular.x = 0; twist.angular.y = 0; twist.angular.z = control_turnpub.publish(twist)except:print(e)finally:twist = Twist()twist.linear.x = 0; twist.linear.y = 0; twist.linear.z = 0twist.angular.x = 0; twist.angular.y = 0; twist.angular.z = 0pub.publish(twist)termios.tcsetattr(sys.stdin, termios.TCSADRAIN, settings)

大概就是在78、79、93、95、141行上的print输出语句上加上（）。

如果写的有什么问题，欢迎大家在评论区留言讨论。

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