020 格式化输出的三种方式

格式化输出的三种方式

符合某种规范的打印输出

1.占位符

程序中常常会有这样场景：要求用户输入信息，而后打印成固定的格式

好比要求用户输入用户名和年龄，而后打印以下格式：My name is xxx，my age is xxx.

很明显，用逗号进行字符串拼接，只能把用户输入的名字和年龄放到末尾，没法放到指定的某个位置，并且数字也必须通过str(数字)的转换才能与字符串进行拼接，很是麻烦，以下例子

age = 19
print('My name is xxx，my age is '+str(age))
My name is xxx，my age is 19

age = 19
print('My name is xxx，my age is', age)
My name is xxx，my age is 19

name = 'nick'
age = 19
print('My name is '+name+' my age is '+str(age))
My name is nick my age is 19

上面使用的方法越看越别扭，越看越麻烦。这就须要用到占位符。

如：%s（针对全部数据类型）、%d（仅仅针对数字类型）

name = 'nick'
age = 19
print('my name is %s my age is %s' % (name, age))
my name is nick my age is 19

age = 19
print('my age is %d' % age)
my age is 19

2.format格式化

name = 'nick'
age = 19
print("Hello, {}. You are {}.".format(name, age))
Hello, nick. You are 19.

name = 'nick'
age = 19
print("Hello, {1}. You are {0}-{0}.".format(age, name))
Hello, nick. You are 19-19.

name = 'nick'
age = 19
print("Hello, {name}. You are {age}-{age}.".format(age=age, name=name))
Hello, nick. You are 19-19.

3.f-Strig格式化

相比较占位符的方式，python3.6版本新增了f-String格式化的方式，比较简单易懂，这是目前我用的最多的方式，推荐使用这种方式。

1.让字符串和数字能够直接相加

name = "nick"
age = 19
print(f"Hello, {name}. You are {age}.")
Hello, nick. You are 19.

2.大写的F也适用。

name = "nick"
age = 19
print(F"Hello, {name}. You are {age}.")
Hello, nick. You are 19.

age = 19
print(f'{age*2}')
38

3.F-string格式化方法还可直接转换成浮点型，以及保留几位小数

s1 = 'nick'  # name
s2 = 'ugly'  # qizhi
s3 = 180     # height

print(f'name:{s1}, qizhi:{s2:->10}, height:{s3:.2f}') 
name:nick, qizhi:------ugly, height:180.00