1.占位符

1.%s：用于插入字符串

name = "Alice"
message = "Hello, %s!" % name
print(message)  # 输出：Hello, Alice!

2. %d：用于插入整数

age = 25
message = "I am %d years old." % age
print(message)  # 输出：I am 25 years old.

3. %f：用于插入浮点数

pi = 3.14159
message = "The value of pi is %.2f." % pi
print(message)  # 输出：The value of pi is 3.14.

4. %x：用于插入十六进制数

number = 255
message = "The hexadecimal representation is %x." % number
print(message)  # 输出：The hexadecimal representation is ff.

5. %o：用于插入八进制数

number = 255
message = "The octal representation is %o." % number
print(message)  # 输出：The octal representation is 377.

6. %r：用于插入任意类型的数据（使用repr()函数进行转换）

data = [1, 2, 3]
message = "The data is %r." % data
print(message)  # 输出：The data is [1, 2, 3].

7. %c：用于插入字符（将整数解释为Unicode字符）

letter = ord('A')
message = "The letter is %c." % letter
print(message)  # 输出：The letter is A.

8. %e 或 %E：用于插入科学计数法表示的浮点数

value = 1.23e+10
message = "The value is %e." % value
print(message)  # 输出：The value is 1.230000e+10.

9. %g 或 %G：用于插入浮点数，自动选择 %f 或 %e（取决于数值大小）

number = 0.0000123456
message = "The number is %g." % number
print(message)  # 输出：The number is 1.23456e-05.

10. %%：用于插入百分号本身

percentage = 75
message = "The success rate is %d%%." % percentage
print(message)  # 输出：The success rate is 75%.

2.转义序列

  在Python中，转义序列是由反斜杠（\）字符紧跟特定字符组成的组合，用于表示一些特殊字符或具有特殊含义的字符。以下是一些常见的Python转义序列及其示例：
1.\ '：单引号

string = 'It\'s a sunny day.'
print(string)  # 输出：It's a sunny day.

2. \ "：双引号

string = "She said, \"Hello!\""
print(string)  # 输出：She said, "Hello!"

3. \\：反斜杠

path = "C:\\Users\\Username\\Documents"
print(path)  # 输出：C:\Users\Username\Documents

4 \n：换行符

message = "Hello,\nWorld!"
print(message)
# 输出：
# Hello,
# World!

5 \t：制表符

message = "Name:\tJohn\tAge:\t25"
print(message)  # 输出：Name:   John    Age:    25

6 \r：回车符

message = "Hello\rWorld!"
print(message)  # 输出：World!

7 \b：退格符

message = "Hello\bWorld!"
print(message)  # 输出：HellWorld!

8 \xhh：十六进制字符（其中 hh 是两位十六进制数）

character = "\x41"
print(character)  # 输出：A