python3.6版本新增了f-strings方法来格式化字符串，我们看一下效果。
示例：
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name = 'liu lin'
age = 29
print("Hello, {}. Your age is {}.".format(name,age)) # old way format
print(f"Hello, {name}. Your age is {age}.") # f-strings format
输出：
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Hello, liu lin. Your age is 29.
Hello, liu lin. Your age is 29.
[Finished in 0.2s]
f-strings格式化字符串，更快，更简洁。对我来说，将来肯定是首选f-strings。
