将列表转换为可分割的浮点数

Question

我一直在努力为全世界制作一个货币转换器。我面临的众多问题之一是我的货币转换器无法计算出汇率本身。你不得不。但当然，我想通了。

但我的问题是：我得到了欧元的汇率，但它是一个列表，我需要它是一个浮点数来进行计算。我该怎么做？

这是我尝试过的：

euro_exchange = float(str(tree.xpath('//div[@class="price"]/text()')))
######################################################################
euro_exchange = tree.xpath('//div[@class="price"]/text()')

float(str(euro_exchange)
################################################################
euro_exchange = float(tree.xpath('//div[@class="price"]/text()')

你得到了模式。当我尝试euro_exchange = float(str(tree.xpath('//div[@class="price"]/text()'))) 时，它说（我正在使用 TkInter，顺便说一句）：

Exception in Tkinter callback
Traceback (most recent call last):
  File "/usr/lib/python3.5/tkinter/__init__.py", line 1562, in __call__
    return self.func(*args)
  File "/home/jboyadvance/Documents/Code/Python/Currency Converter/Alpha2/main.py", line 21, in usd_callback
    euro_exchange = float(str(tree.xpath('//div[@class="price"]/text()')))
ValueError: could not convert string to float: "['1.1394']"

当我尝试euro_exchange = tree.xpath('//div[@class="price"]/text()') float(str(euro_exchange) 时，我得到了相同的结果。

当我尝试euro_exchange = float(tree.xpath('//div[@class="price"]/text()')：

Exception in Tkinter callback
Traceback (most recent call last):
  File "/usr/lib/python3.5/tkinter/__init__.py", line 1562, in __call__
    return self.func(*args)
  File "/home/jboyadvance/Documents/Code/Python/Currency Converter/Alpha2/main.py", line 21, in usd_callback
    euro_exchange = float(tree.xpath('//div[@class="price"]/text()'))
TypeError: float() argument must be a string or a number, not 'list'

这里是源代码：

import tkinter as tk
from lxml import html
import requests

window = tk.Tk()

window.title("Currency Converter")

window.geometry("500x500")

window.configure(bg="#900C3F")

# window.wm_iconbitmap("penny.ico")

page = requests.get('https://www.bloomberg.com/quote/EURUSD:CUR')
tree = html.fromstring(page.content)


def usd_callback():
    usd_amount = float(ent_usd.get())
    euro_exchange = float(str(tree.xpath('//div[@class="price"]/text()')))

    euro_amount = usd_amount / euro_exchange

    lbl_euros.config(text="Euro Amount: %.2f€" % euro_amount)


lbl_usd = tk.Label(window, text="Enter the USD ($) here:", bg="#900C3F", font="#FFFFFF")
ent_usd = tk.Entry(window)

btn_usd = tk.Button(window, text="Convert", command=usd_callback, bg="#FFFFFF", font="#FFFFFF")

lbl_euros = tk.Label(window)

lbl_usd.pack()
ent_usd.pack()

btn_usd.pack()

window.mainloop()

任何帮助将不胜感激！谢谢！！

Answer 1

您需要从xpath 的返回值转换第一个元素：

euro_exchange = tree.xpath('//div[@class="price"]/text()')
euro_exchange = float(str(euro_exchange[0]))