类型错误：+ 不支持的操作数类型：“NoneType”和“float”，同时循环和添加

Question

while running the below code I am getting TypeError: unsupported operand type(s) for +: 'NoneType' and 'float' As per my requirement, I have a list of floating points numbers as string from an API, I want to convert them to float and find the avg

a= None
l=['2.35','4.25','9.9']
for num in l:
  a=a+float(num)
avg=a/len(l)

Answer 1

You should initiate your variable a to 0 instead of None . This will give you:

a = 0
l=['2.35','4.25','9.9']
for num in l:
  a=a+float(num)
avg=a/len(l)

The error you have tells you that you cannot sum a None object with a float, which is exactly what you are trying to do at your first iteration of for loop.

When you initiate your variable a to 0 , you instead perform an addition of two numerical values, which is accepted by Python.