将日期转换为字符串导致字符串中出现“None”，但在 python 中没有错误

问：

我正在尝试创建一个电子邮件正文，然后我将能够发送，代码可以工作并返回我期望的值，直到：

email_text = "Please can you " + str(move_plates) + " and " + str(read_plates)

当我使用时：print(email_text)

然后我得到“请你无和无”但没有错误，任何人都可以建议如何解决这个问题吗？

当我将日期转换为字符串时，我假设这是一个问题。

def move_Plates():
    if _days_[movePlates.weekday()] == "Saturday":
        return ("change day " + str(_days_[movePlates.weekday()]) + "New Date: " + str(movePlates + timedelta(days = 2)))
    elif _days_[movePlates.weekday()] == "Sunday":
        return ("change day " + str(_days_[movePlates.weekday()]) + "New Date: " + str(movePlates + timedelta(days = 1)))
    else: 
        return (" move plates on: " + str(_days_[movePlates.weekday()]) + " " + str(movePlates))
move_plates = print(move_Plates())
move_plates

def read_Plates():
    if _days_[readPlates.weekday()] == "Saturday":
        return ("change day " + str(_days_[readPlates.weekday()])+ "New Date: " + str(movePlates + timedelta(days = 2)))
    elif _days_[readPlates.weekday()] ==  "Sunday":
        return ("change day " + str(_days_[readPlates.weekday()])+ "New Date: " + str(movePlates + timedelta(days = 1)))
    else: 
        return (" read plates on: " + str(_days_[readPlates.weekday()]) + " " + str(readPlates))
read_plates = print(read_Plates())
read_plates

email_text = "Please can you " + str(move_plates) + " and " + str(read_plates)
print(email_text)