python之谁能帮我理解这段 Python 代码是如何工作的

这是我在学校类里面的一个类的代码，我对列表的打印方式感到困惑，因为它总是以“无”结尾......

def printlist(myList, pointer): 
    print("The List is: ", myList) 
    print("Pointer length: ", pointer) 
    print("The List length is: ", len(myList)) 
    print("The List printed properly:") 
    print(printlistproperly(myList)) 
 
def printlistproperly(myList): 
    thelength = len(myList) 
    for i in range(thelength): 
        print(i, " ", myList[i]) 
 
def popin(myList,pointer): 
    myList.append(input("Enter a value: ")) 
    pointer = len(myList)-1 
    return myList, pointer 
 
def main(): 
    myList = ["Ford","Toyota","Mustang"] 
    pointer = len(myList)-1 
    myList,pointer = popin(myList,pointer) 
    printlist(myList, pointer) 

结果是:

>>> main() 
Enter a value: Dodge 
The List is:  ['Ford', 'Toyota', 'Mustang', 'Dodge'] 
Pointer length:  3 
The List length is:  4 
The List printed properly: 
0   Ford 
1   Toyota 
2   Mustang 
3   Dodge 
None 

我真正的问题是......最后的 None 是什么？它从何而来？我该如何解决？

请您参考如下方法:

在函数 printlist 中，您打印函数 printlistproperly 的结果，它不返回任何内容。因此你得到了 None。解决方案:只需调用 printlistproperly(myList)(不使用 print)。

def printlist(myList, pointer): 
    print("The List is: ", myList) 
    print("Pointer length: ", pointer) 
    print("The List length is: ", len(myList)) 
    print("The List printed properly:") 
    printlistproperly(myList)