如何从文本文件中划分数字？

Question

这是我的文件文本：

Covid-19 Data
Country / Number of infections / Number of Death
USA  124.356  2.236
Netherlands  10.866  771
Georgia  90  NA
Germany  58.247  455

我创建了一个函数来计算死亡人数与感染人数的比率，但是它不起作用，因为有些值不是浮点数。

f=open("myfile.txt","w+")

x="USA" + " " + " " + "124.356" + " " + " " + "2.236"
y="Netherlands" + " " + " " + "10.866" + " " + " " + "771"
z="Georgia" + " " + " " + "90" + " " + " " + "NA"
w="Germany" + " " + " " + "58.247" + " " + " " + "455"

f.write("Covid-19 Data" + "\n" + "Country" + " " + "/" + " " + "Number of infections" + " "  + "/" + " " + "Number of Death" + "\n")
f.write(x + "\n")
f.write(y + "\n")
f.write(z + "\n")
f.write(w)

f.close()

with open("myfile.txt", "r") as file:


        try:
            for i in file:
                t = i.split()
                    result=float(t[-1])/float(t[-2])
                    print(results)
        except:
            print("fail")
        file.close()

有人知道如何解决这个问题吗？

Answer 1

您可以执行以下操作：

with open("myfile.txt", "r") as file:
    for i in file:
      t = i.split()

      try:
        result = float(t[-1]) / float(t[-2])
        print(result)
      except ValueError:
        pass

当时您不知道要除的值是否是数值，因此用 try-catch 包围操作应该可以解决您的问题。

如果你想变得更"clean"，你可以这样做：

def is_float(value):
  try:
    float(value)
  except ValueError:
    return False

  return True

with open("myfile.txt", "r") as file:
    for i in file:
      t = i.split()
      if is_float(t[-1]) and is_float(t[-2]):
        result = float(t[-1]) / float(t[-2])
        print(result)

然而，想法是一样的。

Answer 2

文件中的 header 行是 Covid-19 Data。这是第一行，当您调用 t=i.split() 时，您会得到一个包含数据 ['Covid-19', 'Data']

的列表 t

你不能把它们转换成浮点数，因为它们里面有字母。相反，您应该在循环之前阅读前 2 header 行并且不对它们执行任何操作。但是，您将遇到乔治亚州的问题，因为 "NA" 也无法转换为浮点数。

另外几点，捕获所有异常不是好的做法。此外，如果您使用 with 语句打开文件，则无需显式关闭文件。

Answer 3

我使用了您在示例中附加的相同文件。我创建了这个函数，希望它能有所帮助：

with open("test.txt","r") as reader:
    lines = reader.readlines()

for line in lines[2:]:
    line = line.replace(".","") # Remove points to have the full value
    country, number_infections, number_deaths = line.strip().split()
    try:
        number_infections = float(number_infections)
        number_deaths = float(number_deaths)
    except Exception as e:
        print(f"[WARNING] Could not convert Number of Infections {number_infections} or Number of Deaths {number_deaths} to float for Country: {country}\n")
        continue
    ratio = number_deaths/number_infections
    print(f"Country: {country} D/I ratio: {ratio}")

如您所见，我使用 lines[2:] 避免了文件的 headers，这意味着我将从文件的第 3 行开始。此外，添加了 try/exception 逻辑以避免 non-float 转换。希望这对您有所帮助！

编辑刚刚注意到千位的格式与“。”一起使用。而不是 "," 在这种情况下，句点在 line 7.

中被删除

这次执行的结果是：

Country: USA D/I ratio: 0.017980636237897647
Country: Netherlands D/I ratio: 0.07095527332965212

[WARNING] Could not convert Number of Infections 90.0 or Number of Deaths NA to float for Country: Georgia

Country: Germany D/I ratio: 0.007811561110443456

Answer 4

修复了以下内容：

您 text-file 中的前两行是 headers。这些需要跳过
'NA'无法转换为零
如果你的数据中有一个 0，你的程序就会崩溃。现在不会了。

f=open("myfile.txt","w+")

x="USA" + " " + " " + "124.356" + " " + " " + "2.236"
y="Netherlands" + " " + " " + "10.866" + " " + " " + "771"
z="Georgia" + " " + " " + "90" + " " + " " + "NA"
w="Germany" + " " + " " + "58.247" + " " + " " + "455"

f.write("Covid-19 Data" + "\n" + "Country" + " " + "/" + " " + "Number of infections" + " "  + "/" + " " + "Number of Death" + "\n")
f.write(x + "\n")
f.write(y + "\n")
f.write(z + "\n")
f.write(w)

f.close()

with open("myfile.txt", "r") as file:

        #Skipping headers
        next(file)
        next(file)

        try:
            for i in file:
                t = i.split()

                #Make sure your code keeps working when one of the numbers is zero
                x = 0
                y = 0

                #There are some NA's in your file. Strings not representing
                #a number can't be converted to float
                if t[1] != "NA":
                    x = t[1]
                if t[2] != "NA":
                    y = t[2]

                if x == 0 or y == 0:
                    result = 0
                else:
                    result=float(x)/float(y)

                print(t[0] + ": " + str(result))

        except:
            print("fail")
file.close()

输出：

USA: 55.615384615384606
Netherlands: 0.014093385214007782
Georgia: 0
Germany: 0.12801538461538461

如何从文本文件中划分数字？

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