在Python中,如何将列表中的所有项目都转换为浮点数?

问题:在Python中,如何将列表中的所有项目都转换为浮点数?

我有一个脚本,该脚本读取文本文件,将十进制数字作为字符串从中提取出来并将它们放入列表中。

所以我有这个清单:

['0.49', '0.54', '0.54', '0.54', '0.54', '0.54', '0.55', '0.54', '0.54',  '0.54', 
 '0.55', '0.55', '0.55', '0.54', '0.55', '0.55', '0.54', '0.55', '0.55', '0.54']

如何将列表中的每个值从字符串转换为浮点数?

我努力了:

for item in list:
    float(item)

但这似乎对我不起作用。

I have a script which reads a text file, pulls decimal numbers out of it as strings and places them into a list.

So I have this list:

['0.49', '0.54', '0.54', '0.54', '0.54', '0.54', '0.55', '0.54', '0.54',  '0.54', 
 '0.55', '0.55', '0.55', '0.54', '0.55', '0.55', '0.54', '0.55', '0.55', '0.54']

How do I convert each of the values in the list from a string to a float?

I have tried:

for item in list:
    float(item)

But this doesn’t seem to work for me.


回答 0

[float(i) for i in lst]

确切地说,它将创建一个带有浮点值的新列表。与该map方法不同,它将在py3k中工作。

[float(i) for i in lst]

to be precise, it creates a new list with float values. Unlike the map approach it will work in py3k.


回答 1

map(float, mylist) 应该这样做。

(在Python 3中,map不再返回列表对象,因此,如果您想要一个新列表而不只是要迭代的内容,则需要list(map(float, mylist)-或使用SilentGhost的答案(可以说是更Python的)。)

map(float, mylist) should do it.

(In Python 3, map ceases to return a list object, so if you want a new list and not just something to iterate over, you either need list(map(float, mylist) – or use SilentGhost’s answer which arguably is more pythonic.)


回答 2

float(item)做正确的事情:它将其参数转换为float并返回,但不会就地更改参数。您的代码的一个简单修正是:

new_list = []
for item in list:
    new_list.append(float(item))

使用列表理解,可以将相同的代码写得更短: new_list = [float(i) for i in list]

要就地更改列表:

for index, item in enumerate(list):
    list[index] = float(item)

顺便说一句,请避免将其list用于变量,因为它会伪装具有相同名称的内置函数。

float(item) do the right thing: it converts its argument to float and and return it, but it doesn’t change argument in-place. A simple fix for your code is:

new_list = []
for item in list:
    new_list.append(float(item))

The same code can written shorter using list comprehension: new_list = [float(i) for i in list]

To change list in-place:

for index, item in enumerate(list):
    list[index] = float(item)

BTW, avoid using list for your variables, since it masquerades built-in function with the same name.


回答 3

这将是另一种方法(不使用任何循环!):

import numpy as np
list(np.float_(list_name))

This would be the an other method (without using any loop!):

import numpy as np
list(np.float_(list_name))

回答 4

你甚至可以通过numpy做到这一点

import numpy as np
np.array(your_list,dtype=float)

返回列表的np数组为float

您也可以将’dtype’设置为int

you can even do this by numpy

import numpy as np
np.array(your_list,dtype=float)

this return np array of your list as float

you also can set ‘dtype’ as int


回答 5

您可以使用numpy将列表直接转换为浮动数组或矩阵。

    import numpy as np
    list_ex = [1, 0] # This a list
    list_int = np.array(list_ex) # This is a numpy integer array

如果要将整数数组转换为浮点数组,请添加0。

    list_float = np.array(list_ex) + 0. # This is a numpy floating array

You can use numpy to convert a list directly to a floating array or matrix.

    import numpy as np
    list_ex = [1, 0] # This a list
    list_int = np.array(list_ex) # This is a numpy integer array

If you want to convert the integer array to a floating array then add 0. to it

    list_float = np.array(list_ex) + 0. # This is a numpy floating array

回答 6

这就是我要做的。

my_list = ['0.49', '0.54', '0.54', '0.54', '0.54', '0.54', '0.55', '0.54', 
    '0.54', '0.54', '0.55', '0.55', '0.55', '0.54', '0.55', '0.55', '0.54', 
    '0.55', '0.55', '0.54']
print type(my_list[0]) # prints <type 'str'>
my_list = [float(i) for i in my_list]
print type(my_list[0]) # prints <type 'float'>

This is how I would do it.

my_list = ['0.49', '0.54', '0.54', '0.54', '0.54', '0.54', '0.55', '0.54', 
    '0.54', '0.54', '0.55', '0.55', '0.55', '0.54', '0.55', '0.55', '0.54', 
    '0.55', '0.55', '0.54']
print type(my_list[0]) # prints <type 'str'>
my_list = [float(i) for i in my_list]
print type(my_list[0]) # prints <type 'float'>

回答 7

import numpy as np
my_list = ['0.49', '0.54', '0.54', '0.54', '0.54', '0.54', '0.55', '0.54', '0.54', '0.54', '0.55', '0.55', '0.55', '0.54', '0.55', '0.55', '0.54', 
'0.55', '0.55', '0.54']
print(type(my_list), type(my_list[0]))   
# <class 'list'> <class 'str'>

将类型显示为字符串列表。您可以使用numpy同时将此列表转换为浮点数数组:

    my_list = np.array(my_list).astype(np.float)

    print(type(my_list), type(my_list[0]))  
    # <class 'numpy.ndarray'> <class 'numpy.float64'>
import numpy as np
my_list = ['0.49', '0.54', '0.54', '0.54', '0.54', '0.54', '0.55', '0.54', '0.54', '0.54', '0.55', '0.55', '0.55', '0.54', '0.55', '0.55', '0.54', 
'0.55', '0.55', '0.54']
print(type(my_list), type(my_list[0]))   
# <class 'list'> <class 'str'>

which displays the type as a list of strings. You can convert this list to an array of floats simultaneously using numpy:

    my_list = np.array(my_list).astype(np.float)

    print(type(my_list), type(my_list[0]))  
    # <class 'numpy.ndarray'> <class 'numpy.float64'>

回答 8

我必须首先从浮点字符串列表中提取数字:

   df4['sscore'] = df4['simscore'].str.findall('\d+\.\d+')

然后将每个转换为浮点数:

   ad=[]
   for z in range(len(df4)):
      ad.append([float(i) for i in df4['sscore'][z]])

最后,将所有浮点数分配给数据框为float64:

   df4['fscore'] = np.array(ad,dtype=float)

I had to extract numbers first from a list of float strings:

   df4['sscore'] = df4['simscore'].str.findall('\d+\.\d+')

then each convert to a float:

   ad=[]
   for z in range(len(df4)):
      ad.append([float(i) for i in df4['sscore'][z]])

in the end assign all floats to a dataframe as float64:

   df4['fscore'] = np.array(ad,dtype=float)

回答 9

我已经在我的程序中使用以下方法解决了这个问题:

number_input = float("{:.1f}".format(float(input())))
list.append(number_input)

I have solve this problem in my program using:

number_input = float("{:.1f}".format(float(input())))
list.append(number_input)

回答 10

for i in range(len(list)): list[i]=float(list[i])
for i in range(len(list)): list[i]=float(list[i])