Python中f-string字符串格式化的使用

name = "Alice"
 age = 25
 ​
 # 使用 f-string 嵌入变量
 message = f"My name is {name} and I am {age} years old."
 print(message)
 ​
 # 输出 My name is Alice and I am 25 years old.

a = 5
 b = 10
 ​
 # 使用 f-string 嵌入表达式
 result = f"The sum of {a} and {b} is {a + b}."
 print(result)
 ​
 # 输出 The sum of 5 and 10 is 15.

pi = 3.141592653589793
 ​
 # 保留两位小数
 formatted_pi = f"Pi rounded to 2 decimal places: {pi:.2f}"
 print(formatted_pi)
 ​
 #输出 Pi rounded to 2 decimal places: 3.14

number = 42
 ​
 # 补零到 5 位
 formatted_number = f"The number is {number:05d}"
 print(formatted_number)
 ​
 #输出 The number is 00042

population = 1234567890
 ​
 # 添加千位分隔符
 formatted_population = f"The world population is {population:,}"
 print(formatted_population)
 ​
 #输出 The world population is 1,234,567,890

ratio = 0.4567
 ​
 # 格式化为百分比，保留两位小数
 formatted_ratio = f"The ratio is {ratio:.2%}"
 print(formatted_ratio)
 ​
 #输出 The ratio is 45.67%

name = "Alice"
 ​
 # 左对齐，总宽度为 10，用 ' ' 填充
 formatted_name = f"Name: {name:<10}!"
 print(formatted_name)
 ​
 # 右对齐，总宽度为 10，用 '*' 填充
 formatted_name = f"Name: {name:*>10}!"
 print(formatted_name)
 ​
 # 居中对齐，总宽度为 10，用 '=' 填充
 formatted_name = f"Name: {name:=^10}!"
 print(formatted_name)
 ​
 # 输出
 Name: Alice     !
 Name: *****Alice!
 Name: ==Alice===!

long_text = "This is a very long string."
 ​
 # 截断为前 10 个字符
 formatted_text = f"Truncated: {long_text:.10}"
 print(formatted_text)
 ​
 #输出 Truncated: This is a

from datetime import datetime
 ​
 now = datetime.now()
 ​
 # 格式化日期
 formatted_date = f"Today is {now:%Y-%m-%d}"
 print(formatted_date)
 ​
 #输出 Today is 2023-10-05

from datetime import datetime
 ​
 now = datetime.now()
 ​
 # 格式化时间
 formatted_time = f"The time is {now:%H:%M:%S}"
 print(formatted_time)
 ​
 #输出 The time is 14:35:22

number = 1234567890
 ​
 # 科学计数法，保留两位小数
 formatted_number = f"Scientific notation: {number:.2e}"
 print(formatted_number)
 ​
 #输出 Scientific notation: 1.23e+09

number = 255
 ​
 # 二进制
 binary = f"Binary: {number:b}"
 print(binary)
 ​
 # 八进制
 octal = f"Octal: {number:o}"
 print(octal)
 ​
 # 十六进制
 hexadecimal = f"Hexadecimal: {number:x}"
 print(hexadecimal)
 ​
 #输出
 Binary: 11111111
 Octal: 377
 Hexadecimal: ff

name = "alice"
 ​
 # 调用字符串的 title() 方法
 formatted_name = f"Hello, {name.title()}!"
 print(formatted_name)
 ​
 # 输出 Hello, Alice!

person = {"name": "Bob", "age": 30}
 ​
 # 访问字典中的值
 info = f"{person['name']} is {person['age']} years old."
 print(info)
 ​
 numbers = [1, 2, 3, 4, 5]
 ​
 # 访问列表中的元素
 summary = f"The first number is {numbers[0]} and the last number is {numbers[-1]}."
 print(summary)
 ​
 # 输出 
 Bob is 30 years old.
 The first number is 1 and the last number is 5.

name = "Charlie"
 age = 35
 ​
 # 多行 f-string
 message = f"""
 Name: {name}
 Age: {age}
 """
 print(message)
 ​
 # 输出
 Name: Charlie
 Age: 35

a = 5
 b = 10
 ​
 # 嵌套 f-string
 result = f"The sum of {a} and {b} is {f'{a + b}'}."
 print(result)
 ​
 # 输出 The sum of 5 and 10 is 15.