Python将字符串转换为浮点数

We can convert a string to float in Python using float() function. It’s a built-in function to convert an object to floating point number. Internally float() function calls specified object __float__() function.

我们可以使用float（）函数将字符串转换为float在Python中。 它是将对象转换为浮点数的内置函数。 内部float（）函数调用指定的对象__float __（）函数。

Python将字符串转换为浮点数 (Python Convert String to float)

Let’s look at a simple example to convert a string to float in Python.

让我们看一个简单的示例，将字符串转换为浮点数（在Python中）。

s = '10.5674'

f = float(s)

print(type(f))
print('Float Value =', f)

Output:

输出：

<class 'float'>
Float Value = 10.5674

为什么我们需要将字符串转换为float？ (Why do we need to convert a string to float?)

If we are getting float value from user input through the terminal or reading it from a file, then they are string objects. So we have to explicitly convert them to float so that we can perform necessary operations on it, such as addition, multiplication etc.

如果我们通过终端从用户输入中获取浮点值或从文件中读取浮点值，则它们是字符串对象。 因此，我们必须将它们显式转换为float，以便对其执行必要的操作，例如加法，乘法等。

input_1 = input('Please enter first floating point value:\n')
input_1 = float(input_1)

input_2 = input('Please enter second floating point value:\n')
input_2 = float(input_2)

print(f'Sum of {input_1} and {input_2} is {input_1+input_2}')

Python将float转换为String (Python Convert float to String)

We can convert float to a string easily using str() function. This might be required sometimes where we want to concatenate float values. Let’s look at a simple example.

我们可以使用str（）函数轻松地将float转换为字符串。 有时在我们要连接浮点值的地方可能需要这样做。 让我们看一个简单的例子。

f1 = 10.23
f2 = 20.34
f3 = 30.45

# using f-string from Python 3.6+, change to format() for older versions
print(f'Concatenation of {f1} and {f2} is {str(f1) + str(f2)}')
print(f'CSV from {f1}, {f2} and {f3}:\n{str(f1)},{str(f2)},{str(f3)}')
print(f'CSV from {f1}, {f2} and {f3}:\n{", ".join([str(f1),str(f2),str(f3)])}')

Output:

输出：

Concatenation of 10.23 and 20.34 is 10.2320.34
CSV from 10.23, 20.34 and 30.45:
10.23,20.34,30.45
CSV from 10.23, 20.34 and 30.45:
10.23, 20.34, 30.45

If we don’t convert float to string in the above program, join() function will throw exception. Also, we won’t be able to use + operator to concatenate as it will add the floating point numbers.

如果在上述程序中未将float转换为字符串， join（）函数将引发异常。 另外，我们将无法使用+运算符进行连接，因为它将添加浮点数。

Reference: float() official documentation

参考： float（）官方文档

翻译自: https://www.journaldev.com/23715/python-convert-string-to-float