python字符中的变量替换

python3.6后加入了更加简洁的变量替换方式，f放在字符串外面，字符内加了大括号的变量会直接用变量值替换

f"{},{}"

程序如下

name = 'Guido'
n = 37
print(f"{name} has {n} messages.")
Guido has 37 messages.