Question

我从代码中收到以下错误：

File "D:/beverages.py", line XX, in <module>
    relst.append(Residents(float(value[0]),float(value[1]),str(value[2])))
    ValueError: could not convert string to float: '-'

代码如下：

import math

class Residents :
    def __init__(self,x,y,drink):
        self._xco = x
        self._yco = y
        self._drink = drink

    def drink(self):
       return self._drink

    def distance(self,other):
        z = math.sqrt((float(self._xco) - float(other._xco))**2 + (float(self._yco) - float(other._yco))**2)
        return z
    def close(self,other):
        if self.distance(other) < 1:
            return True
        return False

with open("surveydata.txt") as file :
    file1 = file.readline()
    relst = []
    for line in file1 :
        value = line.split()
        relst.append(Residents(float(value[0]),float(value[1]),str(value[2])))

x = input("Input a x-coordinate : ")
y = input("Input a y-coordinate : ")
defau = Residents(x,y,drink = "unknown")

sumcoke = 0
sumpepsi = 0
for res in relst :
    if res.close(defau):
        if res.drink() == "Coke" : 
            sumcoke += 1
        elif res.drink() == "Pepsi": 
            sumpepsi += 1
        pass

print("Number of Coke drinkers are : {0}". format(sumcoke) )
print("Number of Pepsi drinkers are : {0}". format(sumpepsi) )

surveydata.txt文件包含：

-3.043296714578294 -1.8118219429417417  Pepsi
-2.934406412013738 -3.2258867426312845  Pepsi
3.750989559940674 0.6649706751908528  Coke
4.453731061614226 1.1760692786505302  Coke
-3.3141673450571307 2.7471154522861942  Coke
-1.5611978286453065 0.9748847584776836  Coke
-0.6446977323819532 -1.4945077535804119  Pepsi
-4.280039869935868 3.2099331922984433  Coke

我不知道为什么错误会抱怨单个-字符，不是应该处理整个字段（带有符号和的数字）吗？

Answer 1

您的问题就在这里

with open("surveydata.txt") as file:
    file1 = file.readline() # <-- read ONE line
    relst = []
    for line in file1 :
        value = line.split()
        relst.append(Residents(float(value[0]),float(value[1]),str(value[2])))

file1变量仅包含文件的一行（作为字符串），而不包含每一行（作为字符串的集合）。这意味着for line in file1将遍历字符串中的每个 character 而不是集合中的每个 line ，这就是为什么它抱怨单个，单独的{{ 1}}个字符。

因此，您应该将-更改为file1 = file.readline()以读取所有行：

file1 = file.readlines()

此外，尤其是对于较大的文件，遍历文件本身比使用with open("surveydata.txt") as file: file1 = file.readlines() relst = [] for line in file1: value = line.split() relst.append(Residents(float(value[0]),float(value[1]),str(value[2])))效率更高，因为您不会将整个文件加载到内存中。因此，最终代码应如下所示：

.readlines()

打开文件-无法将字符串转换为浮点数：“-”-python

1 个答案: