python中f-string的基本用法

f'string {expression} string'

name = "Alice"
print(f"Hello, {name}!") # 输出：Hello, Alice!

x = 5
y = 10
print(f"The sum of {x} and {y} is {x + y}.") # 输出：The sum of 5 and 10 is 15.

name = 'tom'
age = '18'
# 方法一：
print(f'我是{name},今年{age}岁。')
# 方法二：
print('我是{}，今年{}岁。'.format(name, age))
# 方法三：
print('我是%s,今年%s岁' % (name, age))

name = "Alice"
print(f"Hello, {name}!") # 输出：Hello, Alice!

x = 5
y = 10
print(f"The sum of {x} and {y} is {x + y}.") # 输出：The sum of 5 and 10 is 15.

person = {"name": "Bob", "age": 30}
print(f"{person['name']} is {person['age']} years old.") # 输出：Bob is 30 years old.

def square(x):
        return x ** 2

number = 4
print(f"The square of {number} is {square(number)}.") # 输出：The square of 4 is 16.

pi = 3.141592653589793
print(f"The value of pi is approximately {pi:.2f}.") # 输出：The value of pi is approximately 3.14.

name = 'ready'
print(f'|{name:>20}|')  # 右对齐，填充字符串长度至20
# |               ready|
print(f'{name:<20}')  # 左对齐，填充字符串长度至20
# |ready               |
print(f'{name:^20}')  # 居中对齐，填充字符串长度至20
# |        ready       |

name = 'ready'
print(f'{name:a>20}')
# aaaaaaaaaaaaaaaready
print(f'{name:1<20}')
# ready111111111111111
print(f'{name:-^20}')
# --------ready-------

x = 10
y = 20
 
print(f"x = {x}, y = {y}") # 原方式
# x = 10, y = 20

print(f"{x = }, {y = }")   # 调试模式
# x = 10, y = 20

# 运算x*y的值
print(f"{x * y = }")
# x * y = 200

print(f"{x = :.3f}")
# x = 10.000

name = "Tom" 
print(f"His name is {name!r}.") #输出:His name is'Tom'

name ="Tom"
age=20 
print(f"{'He' if age<18 else 'She'} is {name}.")#输出:She is Tom.

number = 420
 
# decimal places
# 设置精度
print(f"number: {number:.2f}")
 
# hex conversion
# 十六进制转换
print(f"hex: {number:#0x}")
 
# binary conversion
# 二进制转换
print(f"binary: {number:b}")
 
# octal conversion
# 八进制转换
print(f"octal: {number:o}")
 
# scientific notation
# 科学计数法
print(f"scientific: {number:e}") 
 
# total number of characters
# 填充前导0
print(f"Number: {number:09}")

a = 1000000 
print(f"{a= :,}") 
# a= 1,000,000

per = 0.59596
print(f"{per = :.2%}")
# per = 59.60%

import datetime

today = datetime.datetime.utcnow()
print(f"datetime : {today}")
# datetime : 2024-02-28 06:11:04.848944

print(f"date time: {today:%m/%d/%Y %H:%M:%S}") # 没有微秒
# date time: 02/28/2024 06:11:04

print(f"date: {today:%m/%d/%Y}") # 仅日期
# date: 02/28/2024

print(f"time: {today:%H:%M:%S.%f}") # 仅时间
# time: 06:11:04.848944

print(f"time: {today:%H:%M:%S %p}") # 时间带上上午/下午
# time: 06:11:04 AM

print(f"time: {today:%H:%M}") # 24小时制时间
# time: 06:11

print(f"locale appropriate: {today:%c}") # 本地的适当日期和时间表示法
# locale appropriate: Wed Feb 28 06:13:35 2024

print(f"weekday: {today:%A}") # 获取当前日期是星期几
# weekday: Wednesday

print(f"day of year: {today:%j}") # 获取当前日期是一年中的第几天
# day of year: 059

day_of_year = f"{today:%j}" 
print(f"progress % year: {int(day_of_year)/365 * 100:.2f}%")# 获取本年度已过去时间（百分比）
# progress % year: 16.16%

print(f'My name is {'Li Hua'}')
# SyntaxError: f-string: expecting '}'

""" 外部定界符是单引号 """
print(f'My name is {"Li Hua"}')
print(f'My name is {"""Li Hua"""}')

""" 外部定界符是双引号 """
print(f"My name is {'Li Hua'}")
print(f"My name is {'''Li Hua'''}")

""" 外部定界符是双三引号 """
print(f"""My name is {'Li Hua'}""")
print(f"""My name is {"Li Hua"}""")
print(f"""My name is {'''Li Hua'''}""")

""" 外部定界符是单三引号 """
print(f'''My name is {'Li Hua'}''')
print(f'''My name is {"Li Hua"}''')
print(f'''My name is {"""Li Hua"""}''')

print(f'I\'m{"小杨"}') # 输出：I'm小杨
print(f'I\'m{"小杨"},{I\'m OK}')
#输出
'''
print(f'I\'m{"小杨"},{I\'m OK}')
                                     ^
SyntaxError: f-string expression part cannot include a backslash
'''

s = '\''
print(f"{s}")
# '

print(f"给大家推荐一本书{{物种起源}}")
#输出：给大家推荐一本书{物种起源}