Python：如何使用“sum” function 来计算列表中数字的总和？

Question

I'm trying to calculate the sum of multiple numbers in one list, but there always appears an error. These numbers are readed from a txt.

Numbers:

19.18,29.15,78.75,212.10

My code:

infile = open("January.txt","r")
list = infile.readline().split(",")
withdrawal= sum(list)

Error:

withdrawal= sum(list)
TypeError: unsupported operand type(s) for +: 'int' and 'str'

Answer 1

You would need to convert each element from str to float , you can do this with a generator expression.

with open("January.txt","r") as infile:
    data = infile.readline().split(",")
    withdrawal = sum(float(i) for i in data)

Answer 2

The elements of the list are in str format. When they are converted into int or float format, then the sum function will return the sum of the list.

This can be done using the map function as following:

liss=map(float,lis)

Hence:

f=open("January.txt", "r")
lis = f.readline().split(",")
liss=map(float,lis)
withdrawal= sum(liss)
print(withdrawal)

This will produce the desired output.

Hope this was helpful!