字符串格式化

更具体的在这里：https://www.cnblogs.com/wupeiqi/articles/5484747.html

字符串格式化，使用更便捷的形式实现字符串的拼接。

1.1 %输出

1.1.1基本格式化操作

name='yunki'
age=18
text='I am %s, I am 18 years old.' % name
text='I am %s, I am %d years old.' %(name,age)

name='yunki'
age=18
text='I am %(name)s, I am %(age)d years old.' % {'name':name,'age':age}

1.2 百分比表示

一旦字符串格式化中存在百分比的显示，一定要加两个百分号，以实现输出%

name='yunki'
text='%s is 50%%'% name
print(text)
# output: yunki is 50%

1.2 format(推荐)

name='yunki'
age=18
text='i am {0}, I am 18 years old.'.format(name)
text='i am {0}, I am {1} years old.'.format(name,age)
text='i am {0}, I am {1} years old, real name is {0}.'.format(name,age)

name='yunki'
age=18
text='i am {}, I am 18 years old.'.format(name)
text='i am {}, I am {} years old.'.format(name,age)
text='i am {}, I am {} years old, real name is {}.'.format(name,age,name)

name='yunki'
age=18
text='i am {name}, I am 18 years old.'.format(name=name)
text='i am {name}, I am {age} years old.'.format(name=name,age=age)
text='i am {name}, I am {age} years old, real name is {name}.'.format(name=name,age=age)

name='yunki'
age=18
text='i am {0}, I am {1} years old.'.format(name,age)
data1=text.format(name,age)
data2=text.format('ali',15)

1.3 f ‘{string}’（python 3.6++）

name='yunki'
age=18
text=f'I am {name},I am {age} years old.'

name='yunki'
age=18
text=f'I am {name},I am {age+2} years old.'
# text=I am yunki,I am 20 years old.

# 在python3.8引入
name='yunki'
age=18
text=f'I am {name},I am {age+2=} years old.'
# text=I am yunki,I am age+2=20 years old.

# 进制转换
age=18
a1=f'I am {age} years old'
a2=f'I am {age:#b} years old'
a3=f'I am {age:#o} years old'
a4=f'I am {age:#x} years old'
# output:
# I am 18 years old
# I am 0b10010 years old
# I am 0o22 years old
# I am 0x12 years old

name='yunki'
age=18

text=f'I am {'yunki'}.'
# I am yunki.

name='yunki'
text=f'I am {name}.'
# I am yunki.

name='yunki'
text=f'I am {name.upper()}.'
# I am YUNKI.