将字符串转换为 f 字符串

将字符串转换为 f 字符串

问题描述:

如何将经典字符串转换为 f 字符串?

How do I transform a classic string to an f-string?

variable = 42
user_input = "The answer is {variable}"
print(user_input)

输出:答案是{variable}

f_user_input = # Here the operation to go from a string to an f-string
print(f_user_input)

期望输出:答案是42

f 字符串是语法,而不是对象类型.您不能将任意字符串转换为该语法,该语法会创建一个字符串对象,而不是相反.

An f-string is syntax, not an object type. You can't convert an arbitrary string to that syntax, the syntax creates a string object, not the other way around.

我假设您想使用 user_input 作为模板,所以只需使用 str.format() 方法 user_input 对象:

I'm assuming you want to use user_input as a template, so just use the str.format() method on the user_input object:

variable = 42
user_input = "The answer is {variable}"
formatted = user_input.format(variable=variable)

如果你想提供一个可配置的模板服务,创建一个包含所有可以插入的字段的命名空间字典,并使用 str.format()**kwargs> 调用语法来应用命名空间:

If you wanted to provide a configurable templating service, create a namespace dictionary with all fields that can be interpolated, and use str.format() with the **kwargs call syntax to apply the namespace:

namespace = {'foo': 42, 'bar': 'spam, spam, spam, ham and eggs'}
formatted = user_input.format(**namespace)

然后用户可以在 {...} 字段中使用命名空间中的任何键(或者没有,忽略未使用的字段).

The user can then use any of the keys in the namespace in {...} fields (or none, unused fields are ignored).