Question

我得到一个Typecast - 错误，当我尝试转换unicode-strings，从网站解析。以下是相关的代码：

# special IPython command to prepare the notebook for matplotlib

%matplotlib inline 

from fnmatch import fnmatch

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
import requests
from pattern import web

# set some nicer defaults for matplotlib
from matplotlib import rcParams

#these colors come from colorbrewer2.org. Each is an RGB triplet
dark2_colors = [(0.10588235294117647, 0.6196078431372549, 0.4666666666666667),
                (0.8509803921568627, 0.37254901960784315, 0.00784313725490196),
                (0.4588235294117647, 0.4392156862745098, 0.7019607843137254),
                (0.9058823529411765, 0.1607843137254902, 0.5411764705882353),
                (0.4, 0.6509803921568628, 0.11764705882352941),
                (0.9019607843137255, 0.6705882352941176, 0.00784313725490196),
                (0.6509803921568628, 0.4627450980392157, 0.11372549019607843),
                (0.4, 0.4, 0.4)]

rcParams['figure.figsize'] = (10, 6)
rcParams['figure.dpi'] = 150
rcParams['axes.color_cycle'] = dark2_colors
rcParams['lines.linewidth'] = 2
rcParams['axes.grid'] = True
rcParams['axes.facecolor'] = '#eeeeee'
rcParams['font.size'] = 14
rcParams['patch.edgecolor'] = 'none'

def get_poll_xml(id):
    poll = requests.get("http://charts.realclearpolitics.com/charts/"+str(id)+".xml").text
    return poll

import re

def _strip(s):

    return re.sub(r'[\W_]+', '', s)

def plot_colors(xml):

    dom = web.Element(xml)
    result = {}
    for graph in dom.by_tag('graph'):
        title = _strip(graph.attributes['title'])
        result[title] = graph.attributes['color']
    return result

def rcp_poll_data(xml):
    dates = []
    graph1 = []
    graph2 = []
    data = web.Element(xml)
    for item in data.by_tag('series')[0].by_tag('value'):
        dates.append(item.content)
    for item in data.by_tag('graph')[0].by_tag('value'):
        graph1.append(float(unicode(item.content)))
    for item in data.by_tag('graph')[1].by_tag('value'):
        graph2.append(float(unicode(item.content)))
    return pd.DataFrame({'Date': pd.to_datetime(dates), data.by_tag('graph')[0].title: graph1, data.by_tag('graph')[1].title: graph2})

执行此代码时：

print rcp_poll_data(get_poll_xml(1044))

然后我收到以下错误：

---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-8-76ebd15c4a1d> in <module>()
----> 1 print rcp_poll_data(get_poll_xml(1044))

<ipython-input-7-02e6590229d7> in rcp_poll_data(xml)
     53         dates.append(item.content)
     54     for item in data.by_tag('graph')[0].by_tag('value'):
---> 55         graph1.append(float(unicode(item.content)))
     56     for item in data.by_tag('graph')[1].by_tag('value'):
     57         graph2.append(float(unicode(item.content)))

ValueError: could not convert string to float:

我已尝试直接转换为float(item.count)或通过字符串float(string(item.count))，但我总是遇到类型错误...

如果有人可以提供帮助或者可以向我发送主题，我可以在那里找到解决方案，我会很高兴的。我不知道在哪里寻找错误。

THX

Answer 1

我检查了您在代码中检索到的the xml file，发现以value开头的xid="1824"元素没有内容，因此当您尝试转换时，您会得到一个空字符串，会引发错误它是浮动的。解决方案是在转换为float之前检查item.content的内容是否为空。

for item in data.by_tag('graph')[0].by_tag('value'):
    if item.content:
        graph1.append(float(unicode(item.content)))

在上面的for循环之后，你必须进行相同的修正。

Python：ValueError：无法将字符串转换为float：

1 个答案: