Python string 要么 fraction 要么 float to float

Question

我有一个问题，我想获取一个字符串，它可以表示像“1/6”这样的分数或浮点数“2.0”，并让它们都计算为最终的浮点值。我不知道该怎么做是处理这两种情况出现的可能性或如何处理它们以便我得到分数的浮点输出。

numberArray = []
d1 = 0
d2 = 0

fileInput = f.readlines()

for line in fileInput:
    numberArray.append(line)

for i in numberArray:
    content = i.replace("\n","").split(" ")

    d1 = (float(content[0]))
    //The rest of data in the line is stored below (d2, d3 etc), but this isn't 
    // important. The important part is the first item that comes up in each line, 
    //and whether or not it is a fraction or already a float.

输入：

1/3 ...(rest of the line, not important)
2.0 ...

输出：

d1 (line1, item1) = 0.33
d2 (line1, item2) = ...

d1 (line2, item1) = 2.0
d2 (line2, item2) = ...

Answer 1

我是 python 的新手，所以这可能不是最优雅的解决方案，但可能类似于：

import re

values = ["3.444", "3", "1/3", "1/5"]

def to_float(str):
    is_frac = bool(re.search("/", str))
    if is_frac:
        num_den = str.split("/")
        return float(num_den[0]) / float(num_den[1])
    else:
        return float(str)

floats = [to_float(i) for i in values]
print(floats)

Answer 2

The fractions.Fraction constructor already knows how to parse both float-like strings and fraction-like strings，并产生 Fraction 结果。例如：

>>> from fractions import Fraction
>>> float(Fraction('1/3'))
0.3333333333333333
>>> float(Fraction('2.0'))
2.0

因为Fraction可以转换成float，所以可以用这个无条件的产生一个float的结果：

from fractions import Fraction

for line in f:
    content = line.strip('\r\n').split(" ")

    d1 = float(Fraction(content[0]))
    # The rest of data in the line is stored below (d2, d3 etc), but this isn't 
    # important. The important part is the first item that comes up in each line, 
    # and whether or not it is a fraction or already a float.

我冒昧地大大简化了您的代码； f.readlines() 已经 return 一个 list，所以再次迭代它来填充 numberArray 是没有意义的，因为你似乎只填充 numberArray 来迭代它一次无论如何，直接迭代文件比制作两个毫无意义的临时文件更简单。如果你真的需要 list，你只需这样做：

numberArray = f.readlines()
for line in numberArray:

加载一次list并直接存储，而不是逐个元素复制。

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