python之字面量插值

• 字面量：以变量或常量给出的原始值，在程序中可以直接使用字面量。

• 字面量插值：将变量与常量以及表达式插入的一种技术，可以避免字符串拼接问题。

字面量插值通常有以下三种方法：

格式化输出 %

% 操作符可以实现字符串格式化，属于旧式格式化输出，建议使用其它两种方法。

转换说明符	解释
%s	使用str()函数将表达式转换为字符串
%d	转换为带符号的十进制整数
%f	转换为十进制浮点数

>>> name = "Tom"
>>> age = 18
>>> height = 176.66666
>>> print('my name is %s, age is %d and height is %0.2f' % (name, age, height))

my name is Tom, age is 18 and height is 176.67

string.format()

通过format函数传值。列表通过在变量前加*来访问元素。字典通过在变量前加**来访问键值。

name = "Tom"
age = 18
height = 176.66666
list = ['Tom', 18, 176.66666]
dict = {'name':'Tom', 'age':18, 'height':176.66666}
print('my name is {}, age is {} and height is {:.2f}'.format(name, age, height))
print('my name is {0}, age is {1} and height is {2:.2f}'.format(*list))
print('my name is {name}, age is {age} and height is {height:.2f}'.format(**dict))

my name is Tom, age is 18 and height is 176.67

f-string

f-string 是 python3.6 之后版本添加的，称之为字面量格式化字符串，是新的格式化字符串的语法。

f-string 格式化字符串以 f 开头，后面跟着字符串，字符串中的表达式用大括号 {} 包起来，它会将变量或表达式计算后的值替换进去。

name = "Tom"
age = 18
height = 176.66666
list = ["Tom", 18, 176.66666]
dict = {"name":"Tom", "age":18, "height":176.66666}

print(f'my name is {name}, age is {age} and height is {height:.2f}')
print(f'my name is {list[0]}, age is {list[1]} and height is {list[2]:.2f}')
print(f'my name is {dict["name"]}, age is {dict["age"]} and height is {dict["height"]:.2f}')

my name is Tom, age is 18 and height is 176.67