在 Python 3 中将 str 显式转换为 float

Question

我遇到了 "TypeError: Can't convert 'float' object to str implicitly" 错误，因为我试图用字符串除以浮点数。

我正在尝试将字符串转换为浮点数，但仍然出现错误。

字符串 'empNumber' 全部为数字，但有一个逗号（例如：112,000）- 因此 "replace" 函数去除逗号。当我尝试划分 "final/decimal" 时出现错误。如何修复此类型错误？

def revPerEmployee():
    for ticker in sp500short:
        searchurl = "http://finance.yahoo.com/q/ks?s="+ticker
        f = urlopen(searchurl)
        html = f.read()
        soup = BeautifulSoup(html, "html.parser")

        searchurlemp = "http://finance.yahoo.com/q/pr?s="+ticker+"+Profile"
        femp = urlopen(searchurlemp)
        htmlemp = femp.read()
        soupemp = BeautifulSoup(htmlemp, "html.parser")

        try:
            revenue2 = soup.find("td", text="Revenue (ttm):").find_next_sibling("td").text
            empCount2 = soupemp.find("td", text="Full Time Employees:").find_next_sibling("td").text 

        except:
            revenue2 = "There is no data for this company"
            empCount2 = "There is no data for this company"         

        if revenue2 == "There is no data for this company" or empCount2 == "There is no data for this company":
            lastLetter = ticker+": There is no data for this company"
        else:
            lastLetter = revenue2[len(revenue2)-1:len(revenue2)]
            empNumber = empCount2.replace(",", "")
            decimal = float(empNumber)

        if lastLetter == "B":
            result = revenue2[:-1]
            revNum = float(result)
            final = revNum * 1000000000.0
            revPerEmp = final/decimal
            print(ticker+": "+revPerEmp)

        elif lastLetter == "M":
            result = revenue2[:-1]
            revNum = float(result)
            final = revNum * 1000000.0
            #newnum = "{:0,.2f}".format(final)
            revPerEmp = final/decimal
            print(ticker+": "+revPerEmp)

        elif lastLetter == "K":
            result = revenue2[:-1]
            revNum = float(result)
            final = revNum * 1000.0
            #newnum = "{:0,.2f}".format(final)
            revPerEmp = final/decimal
            print(ticker+": "+revPerEmp)

        else:
            print(lastLetter)

Answer 1

17 + "orange"是废话，数字和字符串不能相加。你要

print("%s: %s" % (ticker, revPerEmp))

（您可以将 %s 切换为其他格式，例如 %.2f），或

print(str(ticker) + ": " + str(revPerEmp))

Answer 2

问题是您的程序假定从 URL 请求中获得的是数字形式的数字，后跟后缀（K、M 或 B）。这没有经过测试。

还有两条改进代码的建议。首先，您确实使用 try ... except 子句来检查何时无法获取数据。如果转换失败，您也可以使用它。消息 "There is no data for this company" 可以打印在 except 子句中。

其次，你有三个非常相似的if子句，表明它们可以被压缩。 python 字典可用于后缀值。

SUFFIX_VALUES = { 'K': 1000.0, 'M': 1000000.0, 'B': 1000000000.0 }
try:
  # taken from your code
  revenue2 = soup.find("td", text="Revenue(ttm):").find_next_sibling("td").text
  empCount2 = soupemp.find("td", text="Full Time Employees:").find_next_sibling("td").text 
  revNum = float(revenue2[:-1])
  empNumber = empCount2.replace(",", "")
  decimal = float(empNumber)
  lastLetter = revenue2[-1]
  final = revNum * SUFFIX_VALUES[lastLetter]
  revPerEmp = final/decimal
  print("%s: %d" % (ticker, revPerEmp))
except:
  print(ticker + ": There is no data for this company")

现在，如果URL请求中缺少数据，如果转换失败，或者后缀错误，程序将执行except子句。

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