总结列表中的十进制数。 Python

Question

i wass trying to print the Training result, However, the test accuracy can not be sumed.

q=(['0.50000', '0.56250', '0.50000', '0.50000'])

sum(q)
TypeError: unsupported operand type(s) for +: 'int' and 'str'

Answer 1

You have a list of str so first you have to convert them to float , which you can do using a generator expression within sum .

>>> sum(float(i) for i in q)
2.0625

Answer 2

Someone should post the imho proper version (see comments below):

>>> sum(map(float, q))
2.0625

Answer 3

sum function uses start value 0

>>> help(sum)
Help on built-in function sum in module builtins:

sum(iterable, /, start=0)
    Return the sum of a 'start' value (default: 0) plus an iterable of numbers

    When the iterable is empty, return the start value.
    This function is intended specifically for use with numeric values and may
    reject non-numeric types.

So adding a int object with a string object will raise TypeError

>>> 0 + '0.50000'
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for +: 'int' and 'str'

In order to fix this you can convert the string object into float object first and then apply the sum function.

Answer 4

you can do it like this:

q=(['0.50000', '0.56250', '0.50000', '0.50000'])
result = 0 # create a variable wich will store the value.

for i in q: # loop over your elements
    result += float(i) # cast your temp variable (i) to float and add each element to result. 
print(result) # escape the loop and print the result variable.

Answer 5

q=([0.50000, 0.56250, 0.50000, 0.50000])
sum(q)

or

q=(['0.50000', '0.56250', '0.50000', '0.50000'])
sum([float(x) for x in q])

Answer 6

Remember that float are prone to rounding errors, to my understanding you can get a little extra precision with:

from decimal import Decimal
my_sum = sum(map(Decimal, q))