python - TypeError:类型为 'NoneType' 的对象没有 len() python

Question

我一直收到这个错误

TypeError: object of type 'NoneType' has no len()

代码如下:

def main():
    myList = [ ]
    myList = read_csv()
    ## myList = showList(myList)
    searchList = searchQueryForm(myList)
    if len(searchList) == 0:
        print("I have nothing to print")
    else:
        showList(searchList)

Answer 1

searchQueryForm 如果找不到任何内容，显然会返回 None。由于您不能将 len 应用于 None，因此您必须明确检查:

if searchList is None or len(searchList) == 0: